Web Publications

W3C Editor's Draft

This version:
https://w3c.github.io/wpub/
Latest published version:
https://www.w3.org/TR/wpub/
Latest editor's draft:
https://w3c.github.io/wpub/
Editors:
Matt Garrish (DAISY Consortium)
Ivan Herman (W3C)
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Copyright © 2025 W3C® (MIT, ERCIM, Keio, Beihang). W3C liability, trademark and permissive document license rules apply.

Abstract

The primary objective of this specification is to define requirements for the production of Web Publications. In doing so, it also defines a framework for creating packaged publication formats, such as EPUB and audiobooks, where a pathway to the Web is highly desirable but not necessarily the primary method of interchange or consumption.

Status of This Document

This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at https://www.w3.org/TR/.

Due to the lack of practical business cases for Web Publications, and the consequent lack of commitment to implement the technology, the Publishing Working Group has chosen to publish this document as a Note and focus on other areas of interest, including developing the manifest format as a separate specification.

This document was still a work in progress at the time of its publication. As a result, anyone seeking to create Web Publications, or implement a reader for them, should read the approach and proposals outlined in this document with an abundance of caution. It is being published to archive the work and allow incubation, should interest emerge in the future to resume its development.

The following aspects of the specification, in particular, were being actively discussed at the time of publication and are considered incomplete or in need of more review:

As well, reviews of the following areas were intended to be undertaken only when the specification stabilized:

This document was published by the Publishing Working Group as an Editor's Draft.

GitHub Issues are preferred for discussion of this specification. Alternatively, you can send comments to our mailing list. Please send them to public-publ-wg@w3.org (archives).

Publication as an Editor's Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.

This document was produced by a group operating under the W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.

This document is governed by the 1 March 2019 W3C Process Document.

Introduction

Scope

This specification defines three key concepts:

  1. a general manifest format to describe publications;
  2. a concrete format using the manifest to represent publications on the Web (Web Publications); and
  3. the rules for using the manifest as the basis for modular extensions that desire a pathway to the Web.

This specification does not attempt to constrain the nature of the publications that can be produced—any type of work that can be represented using Web technologies is in scope. It is also designed to be adaptable to the needs of specific areas of publishing, such as audiobook production, and encourages a modular approach for creating specializations.

As much as possible, this specification leverages existing Open Web Platform technologies to achieve its goal—that being to allow for a measure of boundedness — on and off the Web — without changing the way that the Web itself operates.

Moreover, this specification is designed to adapt automatically to updates to Open Web Platform technologies in order to ensure that conforming publications continue to interoperate seamlessly as the Web evolves (e.g., by referencing the latest published versions instead of specific dated versions).

This specification is also intended to facilitate different user agent architectures for the consumption of Web Publications, or any format derived therefrom. While a primary goal is that traditional Web user agents (browsers) will be able to consume Web Publications, this should not limit the capabilities of any other possible type of user agent (e.g., applications, whether standalone or running within a user agent, or even Web Publications that include their own user interface). As a result, the specification does not attempt to architect required solutions for situations whose expected outcome will vary depending on the nature of the user agent and the expectations of the user (e.g., how to prompt to initiate a Web Publication, or at what point or how much of a Web Publication to cache for offline use).

This specification does not define how user agents are expected to render Web Publications. Details about the types of afforances that user agents can provide to enhance the reading experience for users are instead defined in [PWP-UCR].

Organization

This specification organized into three distinct parts, each of which builds on the previous:

Part I — Publication Manifest

The first part of this specification defines a general manifest format for expressing information about a digital publication. It uses [schema.org] metadata augmented to include various structural properties about publications, and is serialized in [JSON-LD]. This definition is designed to be the basis for all the specific implementations of digital publications. It allows for interoperability between the formats while accommodating variances in the information that needs to be expressed. The actual manifest requirements for a digital publication format are defined by its respective specification.

Part II — Web Publications

The second part of this specification details the Web Publications format for defining and deploying publications on the Web. It explains the requirements for expressing the Web Publication manifest, as well as various implementation details such as the primary entry page and the table of contents. Web Publications are the Web deployment format for all digital publications based on a Publication Manifest, so all such extensions have to remain compatible with the requirements defined in this section.

Part III — Modular Extensions

The third part of this specification defines how create new packaged digital publication formats using the Publication Manifest model. While such formats are not required to be conforming Web Publications in their native state, it has to be possible to create content that can conform to both requirements.

Terminology

This document uses terminology defined by the W3C Note "Publishing and Linking on the Web" [publishing-linking], including, in particular, user, user agent, browser, and address.

Digital Publication

The term digital publication is used to refer to the encoding of a publication in any format that conforms to this specification, whether a Web Publication or a modular extension. All such digital publications share the common manifest format, but differ in their structural and content requirements.

Manifest

A manifest represents structured information about a publication, such as informative metadata, a list of all resources, and a default reading order.

Non-empty

For the purposes of this specification, non-empty is used to refer to an element, attribute or property whose text content or value consists of one or more characters after whitespace normalization, where whitespace normalization rules are defined per the host format.

Web Publication

A Web Publication is a collection of one or more resources, organized together through a manifest into a single logical work with a default reading order. The Web Publication is uniquely identifiable and presentable using Open Web Platform technologies.

Conformance

As well as sections marked as non-normative, all authoring guidelines, diagrams, examples, and notes in this specification are non-normative. Everything else in this specification is normative.

The key words MAY, MUST, MUST NOT, OPTIONAL, RECOMMENDED, REQUIRED, SHOULD, and SHOULD NOT in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.

PART I: Publication Manifest

Introduction

A digital publication is described by its manifest, which provides a set of properties expressed using the JSON-LD [json-ld] format (a variant of JSON [ecma-404] for linked data).

The manifest includes both descriptive properties about the publication, such as its title and author, as well as information about the nature and structure of the publication.

This section describes the construction requirements for manifests, and outlines the general set of properties for use with them.

Authored and Canonical Manifests

Depending on the state of a digital publication, its manifest exists in one of two forms:

Authored Manifest

The Authored Publication Manifest is the serialization of the manifest that the author provides with the digital publication (i.e., prior to be digital publication being processed by a user agent). Note that the author does not have to be human; a machine could automatically produce authored manifests for digital publications.

Canonical Manifest

The Canonical Publication Manifest is a version of the manifest created by user agents when they process the authored manifest and remove all possible ambiguities and incorporate any missing values that can be inferred from another source.

It is possible that an authored manifest is the equivalent of the canonical manifest if there are no ambiguities or missing information, but a canonical manifest only exists after a user agent has inspected the authored manifest as part of the process of obtaining it.

This part of the specification describes the requirements for creating an authored manifest, regardless of the format of the digital publication. Rules for constructing a canonical manifest from the authored manifest are defined for each specific implementation (e.g., the process for Web Publications is described in ).

Web IDL

Although a digital publication's manifest is authored as [json-ld], a user agent processes this information into an internal data structure, which can be in any language, in order to utilize the properties. The exact manner in which this processing occurs, and how the data is used internally, is user agent-dependent and not defined in this specification.

To simplify the understanding of the manifest format for developers, this specification defines an abstract representation of the data structures employed by the manifest using the Web Interface Definition Language (Web IDL) [webidl-1] — the PublicationManifest dictionary.

This definition expresses the expected names, datatypes, and possible restrictions for each member of the manifest. Unlike a typical Web IDL definition, however, user agents are not expected to expose the information in the manifest as an API. The Web IDL language is chosen solely to provide an abstraction of the data model.

It is not necessary to understand the Web IDL definition in order to create digital publications. Authoring requirements are defined in the following sections.

The PublicationManifest Dictionary

dictionary PublicationManifest {
    required sequence<DOMString>         type;
             sequence<DOMString>         id;
             sequence<DOMString>         accessMode;
             sequence<DOMString>         accessModeSufficient;
             sequence<DOMString>         accessibilityFeature;
             sequence<DOMString>         accessibilityHazard;
             LocalizableString           accessibilitySummary;
             sequence<CreatorInfo>       artist;
             sequence<CreatorInfo>       author;
             sequence<CreatorInfo>       colorist;
             sequence<CreatorInfo>       contributor;
             sequence<CreatorInfo>       creator;
             sequence<CreatorInfo>       editor;
             sequence<CreatorInfo>       illustrator;
             sequence<CreatorInfo>       inker;
             sequence<CreatorInfo>       letterer;
             sequence<CreatorInfo>       penciler;
             sequence<CreatorInfo>       publisher;
             sequence<CreatorInfo>       readBy;
             sequence<CreatorInfo>       translator;
             sequence<DOMString>         url;
             DOMString                   duration;
             DOMString                   inLanguage;
             TextDirection               inDirection;
             DOMString                   dateModified;
             DOMString                   datePublished;
             ProgressionDirection        readingProgression = "ltr";
    required sequence<LocalizableString> name;
    required sequence<LinkedResource>    readingOrder;
             sequence<LinkedResource>    resources = [];
             sequence<LinkedResource>    links = [];
};
					

dictionary CreatorInfo {
             sequence<DOMString>         type;
    required sequence<LocalizableString> name;
             DOMString                   id;
             DOMString                   url;
};

enum TextDirection {
    "ltr",
    "rtl",
    "auto"
};

dictionary LocalizableString {
    required DOMString                   value;
             DOMString                   language;
};

enum ProgressionDirection {
    "ltr",
    "rtl"
};

Manifest Contexts

A digital publication's manifest MUST start by setting the JSON-LD context [json-ld]. The context has the following two major components:

Example 1: The context declaration. 
{
    "@context" : ["https://schema.org", "https://www.w3.org/ns/wp-context"],
    …
}

The publication context document adds features to the properties defined in Schema.org (e.g., the requirement for the creator property to be order preserving).

As part of the continuous contacts with Schema.org the additional features defined in the publication context file could migrate to the core Schema.org vocabulary.

Although Schema.org is often referenced using the http URI scheme, the vocabulary is being migrated to use the secure https scheme as its default. This specification requires the use of https when referencing Schema.org in the manifest.

Publication Types

A digital publication's manifest MUST define its Publication Type using the type term [json-ld]. The type MAY be mapped onto CreativeWork [schema.org].

Example 2: Setting a publication's type to CreativeWork. 
{
    "@context" : ["https://schema.org", "https://www.w3.org/ns/wp-context"],
    "type"     : "CreativeWork",
    …
}

Schema.org also includes a number of more specific subtypes of CreativeWork, such as Article, Book, TechArticle, and Course. These MAY be used instead of, or in addition to, CreativeWork.

Example 3: Setting a publication's type to Book. 
{
    "@context" : ["https://schema.org", "https://www.w3.org/ns/wp-context"],
    "type"     : "Book",
    …
}

Each Schema.org type defines a set of properties that are valid for use with it. To ensure that the manifest can be validated and processed by Schema.org aware processors, the manifest SHOULD contain only the properties associated with the selected type.

If properties from more than one type are needed, the manifest MAY include multiple type declarations.

Example 4: A publication that combines properties from both Book and VisualArtwork. 
{
    "@context" : ["https://schema.org", "https://www.w3.org/ns/wp-context"],
    "type"     : ["Book", "VisualArtwork"],
    …
}

User agents SHOULD NOT fail to process manifests that are not valid to their declared Schema.org type(s).

Refer to the Schema.org site for the complete list of CreativeWork subtypes.

Properties

Introduction

A digital publication's manifest is defined by a set of properties that describe the basic information a user agent requires to process and render the publication. These properties are categorized as followed:

descriptive properties

Descriptive properties describe aspects of a digital publication, such as its title, creator, and language. These properties are primarily drawn from Schema.org and its hosted extensions [schema.org], so they map to one or several Schema.org properties and inherit their syntax and semantics. (The following property categories typically do not have Schema.org equivalents, so are defined specifically for publications.)

resource categorization

Resource categorization properties describe or identify common sets of resources, such as the resource list and default reading order. These properties refer to one or more resources, such as HTML documents, images, script files, and separate metadata files.

The categorization of properties exists only to simplify comprehension of their purpose; the groupings have no relevance outside this specification (i.e., the properties are not actually grouped together in the manifest).

Each manifest item drawn from schema.org identifies the property it maps to and includes its defining type in parentheses. Properties are often available in many types, however, as a result of the schema.org inheritance model. Refer to each property definition for more detailed information about where it is valid to use.

Schema.org additionally includes a large number of properties that, though relevant for publishing, are not mentioned in this specification — publication authors can use any of these properties. This document defines only the minimal set of manifest items.

There are discussion on whether a best practices document would be created, referring to more schema.org terms. If so, it should be linked from here.

Value Categories

This section describes the categories of values that can be used with properties of the Publication Manifest.

Literals

Some manifest properties expect a literal text string as their value — one that is not language-dependent, such as a code value or date. These values are expressed as [json] strings.

Literal values are not changed during canonicalization of the manifest, unlike other values which might be, for example, converted to objects.

Numbers

Some manifest properties expect a number as their value. These values are expressed as [json] numbers.

Explicit and Implied Objects

Various manifest properties are expected to be expressed as [json] objects. Although the use of objects is usually recommended, it is also acceptable to use string values that are interpreted as objects depending on the context. The exact mapping of text values to objects is part of the property or object definitions.

Localizable Strings

Some manifest properties expect a localizable text string as their value. These values are expressed either as:

  • a single string value;
  • an anonymous object with a value property containing a the property's text and a language property that identifies the language of the text.

In the case of single string values, these represent a implied object whose value property is the string's text and whose language will be determined from other information in the manifest.

Entities

A common case of implied objects in the Publication Manifest properties set is for creators. The entities responsible for the various aspects of creation are expressed as [schema.org] Person and/or Organization objects. To simplify authoring, however, a simple string value can be used for the entity's name. In this case, the entity is assumed to represent a Person.

URLs

URLs are used to identify resources associated with a digital publication. They MUST be valid URL strings [url].

Manifest URLs are restricted to only the http and https schemes [url]. URLs MUST dereference to a resource, although user agents are not required to dereference all URLs in the manifest.

In the case of relative-URL strings, these are resolved to absolute-URL strings using a base URL [url].

The base URL for relative-URL strings is determined as follows:

By consequence, relative-URL strings in embedded manifests are resolved against the URL of the primary entry page unless the page declares a base URL (i.e., in a <base> element in its header).

URLs allow for the usage of characters from Unicode following [rfc3987]. See the note in the HTML5 specification for further details.

Identifiers

Identifiers are URL records [url] that can be used to refer to Web Content in a persistent and unambiguous manner. URLs, URNs, DOIs, ISBNs, and PURLs are all examples of persistent identifiers frequently used in publishing.

Arrays

Some manifest properties allow one or more value of their respective type (literal, object, or URL). As a general rule, these values can be expressed as [json] arrays. When the property value is an array with a single element, however, the array syntax MAY be omitted.

Descriptive Properties

Accessibility

The accessibility properties provides information about the suitability of a digital publication for consumption by users with varying preferred reading modalities. These properties typically supplement an evaluation against established accessibility criteria, such as those provided in [WCAG20]. (For linking to a detailed accessibility report, see .)

The following properties are categorized as accessibility properties:

Term Description Required Value Value Category [schema.org] Mapping
accessMode The human sensory perceptual system or cognitive faculty through which a person may process or perceive information. One or more text(s). Array of Literals accessMode (CreativeWork)
accessModeSufficient A list of single or combined accessModes that are sufficient to understand all the intellectual content of a resource. One or more ItemList. Array of Literals accessModeSufficient (CreativeWork)
accessibilityFeature Content features of the resource, such as accessible media, alternatives and supported enhancements for accessibility. One or more text(s). Array of Literals accessibilityFeature (CreativeWork)
accessibilityHazard A characteristic of the described resource that is physiologically dangerous to some users. One or more text(s). Array of Literals accessibilityHazard (CreativeWork)
accessibilitySummary A human-readable summary of specific accessibility features or deficiencies, consistent with the other accessibility metadata but expressing subtleties such as “short descriptions are present but long descriptions will be needed for non-visual users” or “short descriptions are present and no long descriptions are needed.” Text. Localizable String accessibilitySummary (CreativeWork)

Detailed descriptions of these properties, including the expected values to use with them, are available at [webschemas-a11y].

The author can also provide a reference to a detailed Accessibility Report if more information is needed than can be expressed by these properties.

Example 8: Example accessiblity metadata for a document with text and images. The publication provides alternative text and long descriptions appropriate for each image, so can also be read in purely textual form. 
{
    "@context" : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "type"     : "CreativeWork",
    …
    "accessMode"            : ["textual", "visual"],
    "accessModeSufficient"  : [
        {
            "type"           : "ItemList",
            "itemListElement": ["textual", "visual"]
        },
        {
            "type"           : "ItemList",
            "itemListElement": ["textual"]
        }
    ],
    …
}

Address

A digital publication's address is a URL that identifies its primary entry page. It is expressed using the url property.

Term Description Required Value Value Type [schema.org] Mapping
url URL of the primary entry page. A valid URL string [url]. Array of URLs url (Thing)

A digital publication MAY have more than one address, but all the addresses MUST resolve to the same document.

The publication's address can also be used as value for an identifier link relation [link-relation].
Example 9: Setting the address of the main entry page 
{
    "@context" : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "type"     : "Book",
    …
    "url"      : "https://publisher.example.org/mobydick",
    …
}
Canonical Identifier

A digital publication's canonical identifier property provides a unique identifier for the publication. It is expressed using the id property.

Term Description Required Value Value Type [schema.org] Mapping
id Preferred version of the publication. A URL record [url]. Identifier (None)

The canonical identifier SHOULD be a URL that resolves to the preferred version of the digital publication. Using a URL provides a measure of permanence above and beyond a digital publication's address(es). If a digital publication is permanently relocated to a new URL, for example, the canonical address provides a way of discovering the new location (e.g., a DOI registry could be updated with the new URL, or a redirect could be added to the URL of the canonical identifier). It is also intended to provide a means of identifying instances of the same digital publication hosted at different URLs.

Ensuring uniqueness of canonical identifiers is outside the scope of this specification. The actual achievable uniqueness depends on such factors as the conventions of the identifier scheme used and the degree of control over assignment of identifiers.

If a canonical identifier is not provided in the manifest, or the value is an invalid URL, the digital publication does not have a canonical identifier. User agents MUST NOT attempt to construct a canonical identifier from any other identifiers provided in the manifest for the canonical manifest.

The specification of the canonical identifier MAY be complemented by the inclusion of additional types of identifiers using the identifier property [schema.org] and/or its subtypes.

Example 10: Example of setting the canonical identifier and the address as URLs 
{
    "@context" : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "type"     : "TechArticle",
    …
    "id"       : "http://www.w3.org/TR/tabular-data-model/",
    "url"      : "http://www.w3.org/TR/2015/REC-tabular-data-model-20151217/",
    …
}
Example 11: Example of a URN for the canonical identifier 
{
    "@context" : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "type"     : "Book",
    …
    "id"       : "urn:isbn:9780123456789",
    "url"      : "https://publisher.example.org/mobydick",
    …
}
Creators

A creator is an individual or entity responsible for the creation of the digital publication.

The following properties are categorized as creators:

Term Description Required Value Value Category [schema.org] Mapping
artist The primary artist for the publication, in a medium other than pencils or digital line art. One or more Person. Array of Entities artist (VisualArtwork)
author The author of the publication. One or more Person and/or Organization. Array of Entities author (CreativeWork)
colorist The individual who adds color to inked drawings. One or more Person. Array of Entities colorist (VisualArtwork)
contributor Contributor whose role does not fit to one of the other roles in this table. One or more Person and/or Organization. Array of Entities contributor (CreativeWork)
creator The creator of the publication. One or more Person and/or Organization. Array of Entities creator (CreativeWork)
editor The editor of the publication. One or more Person. Array of Entities editor (CreativeWork)
illustrator The illustrator of the publication. One or more Person. Array of Entities illustrator (Book)
inker The individual who traces over the pencil drawings in ink. One or more Person. Array of Entities inker (VisualArtwork)
letterer The individual who adds lettering, including speech balloons and sound effects, to artwork. One or more Person. Array of Entities letterer (VisualArtwork)
penciler The individual who draws the primary narrative artwork. One or more Person. Array of Entities penciler (VisualArtwork)
publisher The publisher of the publication. One or more Person and/or Organization. Array of Entities publisher (CreativeWork)
readBy A person who reads (performs) the publication (for audiobooks). One or more Person. Array of Entities readBy (Audiobook)
translator The translator of the publication. One or more Person and/or Organization. Array of Entities translator (CreativeWork)

Creators are represented in one of the following two ways:

  1. as a string encoding the name of a Person [schema.org]; or
  2. as an instance of a Person or Organization [schema.org].

In other words, a single string value is a shorthand for a [schema.org] Person whose name property is set to that string value. (See also .)

When compiling each set of creator information from a [schema.org] Person or Organization type, user agents MUST retain the following information when available:

type
One or more strings that identifies the type of creator. This sequence SHOULD include "Person" or "Organization".
name
One or more localizable strings for the name of the creator.
id
A canonical identifier of the creator as an Identifier.
url
An address for the creator in the form of a URL.

Note that user agents MAY interpret a wider range of creator properties defined by Schema.org than the ones in the preceding list.

The manifest MAY include more than one of each type of creator.

Example 12: Author of a book 
{
    "type"     : "Book",
    "@context" : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    …
    "url"      : "https://publisher.example.org/mobydick",
    "author"   : {
        "type"  : "Person",
        "name"  : "Herman Melville"
    }
}
Example 13: Separate listing of editors, authors, and publisher, with some persons expressed as simple strings 
{
    "@context"   : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "type"       : "TechArticle",
    …
    "id"         : "http://www.w3.org/TR/tabular-data-model/",
    "url"        : "http://www.w3.org/TR/2015/REC-tabular-data-model-20151217/",
    "author"     : [
        "Jeni Tennison",
        {
            "type"  : "Person",
            "name" : "Gregg Kellogg",
        },{
            "type"  : "Person",
            "name" : "Ivan Herman",
            "id"   : "https://www.w3.org/People/Ivan/"
        }
    ],
    "editor"    : [
        "Jeni Tennison",
        {
            "type"  : "Person",
            "name" : "Gregg Kellogg",
        }
    ],
    "publisher" : {
        "type"  : "Organization",
        "name" : "World Wide Web Consortium",
        "id"   : "https://www.w3.org/"
    }
    …
}
Duration

The global duration indicates the overall length of a time-based digital publication (e.g., an audiobook, a book consisting of a series of video clips, etc.). It is expressed as a "Duration" value as defined by [iso8601].

Term Description Required Value Value Category [schema.org] Mapping
duration Overall duration of a time-based publication. Duration value as defined by [iso8601] Literal duration (Property)
Example 14: Global duration provided in the manifest (in seconds) 
{
    "@context"       : ["https://schema.org", "https://www.w3.org/ns/wp-context"],
    "type"           : "Audiobook",
    "id"             : "https://example.org/flatland-a-romance-of-many-dimensions/",
    "url"            : "https://w3c.github.io/wpub/experiments/audiobook/",
    "name"           : "Flatland: A Romance of Many Dimensions",
    …		
    "duration"       : "PT15153S",
    …
}

The relevant Wikiepedia page gives a concise description of the ISO duration syntax.

Language and Base Direction

A digital publication has at least one natural language, which is the language that the content is expressed in (e.g., English, French, Chinese). It also has a natural base direction in which it is written — the display direction, either left-to-right or right-to-left.

The digital publication manifest includes entries to set both these concepts, which can influence, for example, the behavior of a user agent (e.g., it might place a pop-up for a table of contents on the right hand side for publications whose natural base direction is right-to-left).

It is important to differentiate the language of the publication from the language and the base direction of the individual resources that compose it. If such resources are, for example, in HTML, the language and direction need to be set in those resources, too. The language and base direction of the publication are not inherited.

Similarly, each natural language property value in the manifest (e.g., title, creators) is a localizable string.

For more information about localized strings on the Web, refer to [string-meta].

The natural language and base direction can be set for both the publication and the natural language properties values of the manifest.

If a user agent requires the language and one is not available in the authored manifest (either globally or specifically for that property), or the obtained value is invalid, the user agent MAY attempt to determine the language when generating the canonical manifest. This specification does not mandate how such a language tag is created. The user agent might:

  • use the non-empty language declaration of the manifest;
  • use the first non-empty language declaration found in a resource in the default reading order;
  • calculate the language using its own algorithm.

No default values are specified for the language or the default base direction.

Global Language and Direction

The manifest MAY include global language and base direction declarations for the publication using the following properties.

Term Description Required Value Value Category [schema.org] Mapping
inLanguage Default language for the publication as well as the textual manifest values language code as defined in [bcp47] Literal inLanguage (Property)
inDirection Default base direction for the publication as well as the textual manifest values ltr, rtl, or auto Literal (None)

The natural language MUST be a tag that conforms to [bcp47], while the base language direction MUST have one of the following values:

  • ltr: indicates that the textual values are explicitly directionally set to left-to-right text;
  • rtl: indicates that the textual values are explicitly directionally set to right-to-left text;
  • auto indicates that the textual values are explicitly directionally set to the direction of the first character with a strong directionality, following the rules of the Unicode Bidirectional Algorithm [bidi].

When specified, these properties are also used as defaults for textual values in the manifest.

The global language information MAY be overridden by individual values.

If the manifest is embedded in the primary entry page via a script element, and the manifest does not set the global language and/or the base direction (see ), the lang and the dir attributes of the script element are used as the global language and base direction, respectively (see the details on handling the lang and dir attributes in [html]).

If authors intend to use a manifest, or a manifest template, both as embedded manifest and as a separate resource, they are strongly encouraged to set these properties explicitly to avoid interference of the containing script element in case of embedding.

Item-specific Language

It is possible to set the language for any textual value in the manifest. This information MUST be set as a localizable string, i.e., using the value and language terms (instead of a simple string) [json-ld]:

Example 15: Setting the author name to French using a localizable string 
{
    "@context" : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "type"     : "Book",
    …
    "author" : {
        "type"  : "Person",
        "name" : {
            "value"    : "Marcel Proust",
            "language" : "fr"
        }
    }
}

The value of the language MUST be set to a language code as defined in [bcp47].

When used in a context of localizable texts, a simple string value is a shorthand for a localizable string, with the value set to the string value, and the language set to the value of the inLanguage property, if applicable, and unset otherwise. In other words, the previous example is equivalent to:

Example 16: Setting the default language of an author name to French 
{
    "@context"   : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "type"       : "Book",
    "inLanguage" : "fr",
    …
	"author"     : "Marcel Proust",
    …	
}

(See also .)

It is not possible to set the direction explicitly for a value.

Setting the direction for a natural text value is currently not possible in JSON-LD [json-ld]. In case the JSON-LD community, as well as the schema.org community, introduces such a feature, future versions of this specification may extend the ability of manifests to include this.

In order to correctly handle manifests entries containing right-to-left or bidirectional text, user agents SHOULD identify the base direction of any given natural language value by scanning the text for the first strong directional character.

In situations where the first-strong heuristics will produce the wrong result (e.g., a string in the Arabic or Hebrew script that begins with a Latin acronym), content developers may want to prepend a Unicode formatting character to the string. This would then produce the necessary base direction when the heuristics are applied. They should use one of the following formatting characters: U+200E LEFT-TO-RIGHT MARK, or U+200F RIGHT-TO-LEFT MARK. (See .)

Once the base direction has been identified, user agents MUST determine the appropriate rendering and display of natural language values according to the Unicode Bidirectional Algorithm [bidi]. This could require wrapping additional markup or Unicode formatting characters around the string prior to display, in order to apply the base direction.

Once the base direction has been identified, user agents MUST determine the appropriate rendering and display of natural language values according to the Unicode Bidirectional Algorithm[bidi]. This could require wrapping additional markup or control characters around the string prior to display, in order to apply the base direction. (See .

Last Modification Date

The last modification date is the date when the digital publication was last updated (i.e., whenever changes were last made to any of the resources of the publication, including the manifest). It is expressed using the dateModified property.

Term Description Required Value Value Category [schema.org] Mapping
dateModified Last modification date of the publication. A Date or DateTime value [schema.org], both expressed in ISO 8601 Date, or Date Time formats, respectively [iso8601]. Literal dateModified (CreativeWork)

The last modification date does not necessarily reflect all changes to the publication (e.g., third-party content could change without the author being aware). User agents SHOULD check the last modification date of individual resources to determine if they have changed and need updating.

Example 17: Last modification date of the publication 
{
    "@context"     : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "type"         : "TechArticle",
    …
    "id"           : "http://www.w3.org/TR/tabular-data-model/",
    "url"          : "http://www.w3.org/TR/2015/REC-tabular-data-model-20151217/",
    "dateModified" : "2015-12-17",
    …
}
Publication Date

The publication date is the date on which the digital publication was originally published. It represents a static event in the lifecycle of a publication and allows subsequent revisions to be identified and compared. It is expressed using the datePublished property.

Term Description Required Value Value Category [schema.org] Mapping
datePublished Creation date of the publication. A Date or DateTime, both expressed in ISO 8601 Date, or Date Time formats, respectively [iso8601]. Literal datePublished (CreativeWork)

The exact moment of publication is intentionally left open to interpretation: it could be when the publication is first made available online or could be a point in time before publication when the publication is considered final.

Example 18: Creation and modification date of the publication 
{
    "@context"      : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "type"          : "TechArticle",
    …
    "id"            : "http://www.w3.org/TR/tabular-data-model/",
    "url"           : "http://www.w3.org/TR/2015/REC-tabular-data-model-20151217/",
    "datePublished" : "2015-12-17",
    "dateModified"  : "2016-01-30",
    …
}
Reading Progression Direction

The reading progression establishes the reading direction from one resource to the next within a digital publication. It is expressed using the readingDirection property.

Term Description Required Value Value Category [schema.org] Mapping
readingProgression Reading direction from one resource to the other. ltr or rtl Literal (None)

The value of this property MUST be either:

  • ltr: left-to-right;
  • rtl: right-to-left.

The default value is ltr.

This property has no effect on the rendering of the individual primary resources; it is only relevant for the progression direction from one resource to the other.

The reading progression of a publication is used to adapt such publication level interactions as menu position, swap direction, defining tap zones to lead the user to the next and previous pages, touch gestures, etc.

If the readingProgression is not set, user agents MUST use the default value ltr when generating the canonical manifest.

Example 19: Reading progression set explicitl to ltr 
{
    "@context"           : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "type"               : "Book",
    …
    "url"                : "https://publisher.example.org/mobydick",
    "readingProgression" : "ltr"
}
Title

The title provides the human-readable name of the digital publication. It is expressed using the name property.

Term Description Required Value Value Category [schema.org] Mapping
name Human-readable title of the publication. One or more text items for the title. Array of Localizable Strings name (Thing)

If a title is not included in the authored manifest, and a digital publication does not define alternative rules for obtaining one, the user agent MUST create one. This specification does not specify what heuristics to use to generate such a title.

A user agent is not expected to produce a meaningful title [wcag20] for a publication when one is not specified.

Example 20: Title of the book set explicitly 
{
    "@context" : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "type"     : "Book",
    …
    "url"      : "https://publisher.example.org/mobydick",
    "name"     : "Moby Dick"
}

Resource Categorization Properties

Publication resources are specified via the default reading order, the resource list, and the links, as defined in this section. These lists contain references to informative resources like the privacy policy, and structural resources like the table of contents.

Note that a particular resource's URL MUST NOT appear in more than one of these lists, and a URL MUST NOT be repeated within a list.

The manifest MUST NOT include a reference to itself within any of these lists.

Default Reading Order

The default reading order is a specific progression through a set of digital publication resources. A user might follow alternative pathways through the content, but in the absence of such interaction the default reading order defines the expected progression from one resource to the next.

The default reading order is expressed using the readingOrder property.

Term Description Required Value Value Category [schema.org] Mapping
readingOrder

One or more of:

  • a string, representing the URL of the resource; or
  • an instance of a LinkedResource object

The order of items is significant. The URLs MUST NOT include fragment identifiers. Non-HTML resources SHOULD be expressed as LinkedResource objects with their encodingFormat values set.

 Array of Links (None)

The default reading order MUST include at least one resource.

Example 21: Reading order expressed as a simple list of URLs 
{
    "@context" : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "type"     : "Book",
    …
    "url"      : "https://publisher.example.org/mobydick",
    "name"     : "Moby Dick",
    "readingOrder" : [
        "html/title.html",
        "html/copyright.html",
        "html/introduction.html",
        "html/epigraph.html",
        "html/c001.html",
        …
    ]
}
Example 22: Reading order expressed as objects providing more information on items 
{
    "@context" : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "type"     : "Book",
    …
    "url"      : "https://publisher.example.org/mobydick",
    "name"     : "Moby Dick",
    "readingOrder" : [{
        "type"           : "LinkedResource",
        "url"            : "html/title.html",
        "encodingFormat" : "text/html",
        "name"           : "Title page"
    },{
        "type"           : "LinkedResource",
        "url"            : "html/copyright.html",
        "encodingFormat" : "text/html",
        "name"           : "Copyright page"
    },{
        …
    }]
}
Resource List

The resource list enumerates any additional resources used in the processing and rendering of a digital publication that are not already listed in the default reading order. It is expressed using the resources property.

Term Description Required Value Value Category [schema.org] Mapping
resources

One or more of:

  • a string, representing the URL of the resource; or
  • an instance of a LinkedResource object

The order of items is not significant. The URLs MUST NOT include fragment identifiers. It is RECOMMENDED to use LinkedResource objects with their encodingFormat values set.

 Array of Links (None)

The completeness of the resource list can affect the usability of a digital publication in certain reading scenarios (e.g., the ability to read it offline). For this reason, it is strongly RECOMMENDED to provide a comprehensive list of all of the publication's constituent resources beyond those listed in the default reading order.

In some cases, a comprehensive list of these resources might not be easily achieved (e.g., third-party scripts that reference resources from deep within their source), but a user agent SHOULD still be able to render a publication even if some of these resources are not identified as belonging to the publication (e.g., if it is taken offline without them).

Example 23: Listing resources, some via a simple URL, some with more details 
{
    "@context"   : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "type"       : "TechArticle",
    …
    "id"         : "http://www.w3.org/TR/tabular-data-model/",
    "url"        : "http://www.w3.org/TR/2015/REC-tabular-data-model-20151217/",
    …
    "resources"  : [
        "datatypes.html",
        "datatypes.svg",
        "datatypes.png",
        "diff.html",
        {
            "type"              : "LinkedResource",
            "url"               : "test-utf8.csv",
            "encodingFormat"    : "text/csv"
        },{
            "type"              : "LinkedResource",
            "url"               : "test-utf8-bom.csv",
            "encodingFormat"    : "text/csv"
        },{
            …
        }
    ],
    …
}

Extensibility

The manifest is designed to provide a basic set of properties for use by user agents in presenting and rendering a digital publication, but MAY be extended in the following ways:

  1. by the provision of linked metadata records.
  2. through the inclusion of additional properties in the manifest;

Although both methods are valid, the use of linked records is RECOMMENDED.

This specification does not define how such additional properties are compiled, stored or exposed by user agents in their internal representation of the manifest. A user agent MAY ignore some or all extended properties.

Linked records

Extending the manifest through links to a record, such as an ONIX [onix] or BibTeX [bibtex] file, MUST be expressed using a LinkedResource object, where:

  • the rel value of the LinkedResource SHOULD include a relevant identifier defined by IANA or by other organizations; if the link record contains descriptive metadata it MUST include the describedby (IANA) identifier;
  • the value of the encodingFormat in the link MUST use the MIME media type [rfc2046] defined for that particular type of record, if applicable.

Linked records MUST be included in the resource list when they are part of the publication (i.e., are needed for more than just manifest extensibility). Otherwise, they MUST be included in the links list.

The application/onix+xml MIME type has not yet been registered by IANA at the time of writing this document, and is included in the example for illustrative purposes only.

Additional Properties in the Manifest

Additional properties can be included directly in the manifest. It is RECOMMENDED that these properties be taken from public schemes like [schema.org] or [dcterms] and use values from controlled vocabularies whenever possible. Proprietary terms MAY be used, but it is RECOMMENDED that such terms be included using Compact IRIs [json-ld], with prefixes defined as part of the context.

Example 25: Usage of the schema.org 'copyrightYear' and 'copyrightHolder' terms, as an extension to the basic data 
{
"@context"        : ["https://schema.org","https://www.w3.org/ns/wp-context"],
"type"            : "TechArticle",
…
"id"              : "http://www.w3.org/TR/tabular-data-model/",
"url"             : "http://www.w3.org/TR/2015/REC-tabular-data-model-20151217/",
"copyrightYear"   : "2015",
"copyrightHolder" : "World Wide Web Consortium",
…
}
Example 26: Usage of the Dublin Core 'subject' with the 2012 ACM Classification terms, as an extension to the basic data 
{
"@context"   : ["https://schema.org","https://www.w3.org/ns/wp-context"],
"type"       : "CreativeWork",
…
"id"         : "http://www.w3.org/TR/tabular-data-model/",
"url"        : "http://www.w3.org/TR/2015/REC-tabular-data-model-20151217/",
"dc:subject" : ["Web data description languages","Data integration","Data Exchange"],
…
}

A prefix definition dc for [dcterms] is included in the context file of [schema.org]. This means that it is not necessary to add the prefix explicitly. The same is true for a number of other public vocabularies; see the schema.org context file for further details.

Resource Relations

Introduction

The manifest identifies key resources of a digital publication through the use of link relations. These relations are applied to the rel property of LinkedResource objects (e.g., the links found in the table of contents and resource list).

The types of resources these relations identify are categorized as follows:

informative resources

Informative resources are resources that contain additional information about the publication, such as its privacy policy, accessibility report, or preview.

structural resources

Structural resources are key meta structures of the publication, such as the cover image, table of contents, and page list.

Informative Resources

Accessibility Report

An accessibility report provides information about the suitability of a digital publication for consumption by users with varying preferred reading modalities. These reports typically identify the result of an evaluation against established accessibility criteria, such as those provided in [WCAG21], and are an important source of information in determining the usability of a publication.

An accessibility report is identified using the accessibility-report link relation.

The accessibility-report term is not currently registered in the IANA link relations but the Working Group expects to add it.

The manifest SHOULD include a link to an accessibility report when one is available for a publication. It is RECOMMENDED that the report be included as a resource of the publication.

It is also RECOMMENDED that the accessibility report be provided in a human-readable format, such as [html]. Augmenting these reports with machine-processable metadata, such as provided in Schema.org [schema.org], is also RECOMMENDED.

Preview

Not all digital publications will be available to all users (e.g., they might be restricted to registered users of a site). In such cases, the publisher might wish to provide a preview of the content in order to entice users to access the full version.

A preview is identified using the preview link relation [iana-link-relations].

Previews MAY be located externally or included as resources of digital publications.

Example 28: A preview is identified as an audio resource of a digital publication 
"@context"   : ["https://schema.org","https://www.w3.org/ns/wp-context"],
"type"       : "Book",
…
"url"        : "https://publisher.example.org/mobydick",
"name"       : "Moby Dick",
"links"  : [{
	"type"            : "LinkedResource",
	"url"             : "preview.mp3",
	"encodingFormat"  : "audio/mpeg",
	"rel"             : "preview"
},{
	…
}],
…
}
Privacy Policy

Users often have the legal right to know and control what information is collected about them, how such information is stored and for how long, whether it is personally identifiable, and how it can be expunged. Including a statement that addresses such privacy concerns is consequently an important part of publishing digital publications. Even if no information is collected, such a declaration increases the trust users have in the content.

A link to a privacy policy can be included in the manifest for this purposes. It is RECOMMENDED that the privacy policy be included as a resource of the publication.

A privacy policy is identified using the privacy-policy link relation [iana-link-relations].

Refer to for more information about privacy considerations in publications.

Structural Resources

Cover

The cover is a resource that user agents can use to present the digital publication (e.g., in a library or bookshelf, or when initially loading the publication).

The cover is identified by the cover link relation. The URL expressed in the url term MUST NOT include a fragment identifier.

The cover term is not currently registered in the IANA link relations but the Working Group expects to add it.

If the cover is in an image format, a title and description SHOULD be provided. User agents can use these properties to provide alternative text and descriptions when necessary for accessibility.

More than one cover MAY be referenced from the manifest (e.g., to provide alternative formats and sizes for different device screens). If multiple covers are specified, each instance MUST define at least one unique property to allow user agents to determine its usability (e.g., a different format, height, width or relation).

Example 31: Cover HTML page 
{
    "@context"   : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "type"       : "Book",
    …
    "url"        : "https://publisher.example.org/donquixote",
    "name"       : "Don Quixote",
    "resources"  : [{
        "type"           : "LinkedResource",
        "url"            : "cover.html",
        "encodingFormat" : "text/html",
        "rel"            : "cover"
    },{
        …
    }],
    …
}
Example 32: Cover image with title and description 
{
    "@context"   : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "type"       : "Book",
    …
    "url"        : "https://publisher.example.org/mobydick",
    "name"       : "Moby Dick",
    "resources"  : [{
        "type"           : "LinkedResource",
        "url"            : "whale-image.jpg",
        "encodingFormat" : "image/jpeg",
        "rel"            : "cover",
        "name"           : "Moby Dick attacking hunters",
        "description"    : "A white whale is seen surfacing from the water to attack a small whaling boat"
    },{
        …
    }],
    …
}
Example 33: Cover image in JPEG and SVG formats 
{
    "@context"   : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "type"       : "Book",
    …
    "url"        : "https://publisher.example.org/donquixote",
    "name"       : "Gulliver's Travels",
    "resources"  : [{
        "type"           : "LinkedResource",
        "url"            : "lilliput.jpg",
        "encodingFormat" : "image/jpeg",
        "rel"            : "cover"
    },{
        "type"           : "LinkedResource",
        "url"            : "lilliput.svg",
        "encodingFormat" : "image/svg+xml",
        "rel"            : "cover"
    },{
        …
    }],
    …
}
Page List

The page list is a navigational aid that contains a list of static page demarcation points within a digital publication.

The page list is identified by the pagelist link relation. The URL expressed in the url term MUST NOT include a fragment identifier.

The pagelist term is not currently registered in the IANA link relations but the Working Group expects to add it.

The link to the page list MAY be specified in either the default reading order or resource-list, but MUST NOT be specified in both.

Example 34: Page list identified in another resource of the publication 
{
"@context"   : ["https://schema.org","https://www.w3.org/ns/wp-context"],
"type"       : "Book",
…
"url"        : "https://publisher.example.org/mobydick",
"name"       : "Moby Dick",
"resources"  : [{
	"type"       : "LinkedResource",
	"url"        : "toc_file.html",
	"rel"        : "pagelist"
},{
	…
}],
…
}
Table of Contents

The table of contents is a navigational aid that provides links to the majort structural sections of a digital publication.

The table of contents is identified by the contents link relation [iana-link-relations]. The URL expressed in the url term MUST NOT include a fragment identifier.

The link to the table of contents MAY be specified in either the default reading order or resource-list, but MUST NOT be specified in both.

Example 35: Resource containing the table of contents identified by its rel attribute value 
{
    "@context"   : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "type"       : "Book",
    …
    "url"        : "https://publisher.example.org/mobydick",
    "name"       : "Moby Dick",
    "resources"  : [{
        "type"       : "LinkedResource",
        "url"        : "toc_file.html",
        "rel"        : "contents"
    },{
        …
    }],
    …
}

Extensions

If additional relations beyond those defined in this specification need to be expressed, the rel property can be extended in one of the following ways:

Use of relations from [iana-relations] is RECOMMENDED.

Association

Embedding

When a manifest is embedded within an HTML document, it MUST be included in a script element [html] whose type attribute is set to application/ld+json.

Additionally, the script element MUST include a unique identifier in an id attribute [html]. This identifier ensures that the manifest can be referenced.

Example 39: A Web Publication Manifest included in an HTML document 
<script id="example_manifest" type="application/ld+json">
   {
      …
   }
</script>

Publication Manifest Lifecycle

Introduction

This section describes the steps a user agent follows to process an authored manifest into an internal representation of the data structure it contains.

The first step in this process is to obtain the manifest, the exact steps by which to do so are typically defined by each digital publication format.

The process then involves generating a canonical form of the manifest, which is a representation that adds any missing data not explicitly authored (e.g., information could be gleaned from a containing HTML document if the manifest is embedded inside a script tag).

After a canonical manifest is generated, the data is put through a final set of post-processing steps to check its validity, ultimately resulting in a data structure that the user agent can use.

Within this process are various extension points that allow digital publication formats to enhance the basic requirements for their own specialized needs and audiences.

Processing a Manifest

The steps for processing a manifest are given by the following algorithm. The algorithm, if successful, returns a processed manifest; otherwise, it terminates prematurely and returns nothing. In the case of nothing being returned, the user agent MUST ignore the manifest declaration.

The algorithm takes the following arguments:

  • text: a UTF-8 string containing the manifest;
  • base: a URL string that represents the base URL for the manifest.
  • document: the HTML Document (DOM) Node of the document that references the manifest.
  1. Let json be the result of parsing text. If parsing throws an error, terminate this algorithm.
  2. If Type(json) is not Object, terminate this algorithm.
  3. Let canonical manifest be the canonical manifest derived from json, using the values of json, base, and document as input to the algorithm described in .

  4. Check whether the canonical manifest fulfills the minimal requirements for a Publication Manifest, namely:

    • the JSON-LD context is set as required in ;
    • the Publication type is set as required in ; and
    • any extension requirements are set as defined in their respective specifications.

    If any of these requirements is not met, terminate the algorithm.

  5. Let processed manifest be the result of post-processing a canonical manifest given canonical manifest.
  6. Return processed manifest.

The algorithm does not describes how error and warning messages should be reported. This is implementation dependent.

Generating a Canonical Manifest

The steps to convert a Publication Manifest into a Canonical Manifest are given by the following algorithm. The algorithm takes the following arguments:

  • manifest: a JSON object that represent the manifest
  • base: a URL string that represents the base URL for the manifest
  • document: the HTML Document (DOM) Node of the document that references the manifest.

The steps of the algorithm are described below. The algorithm varies from strict JavaScript notation in that P["term"] refers to the value in the object P for the label "term", where P is either manifest or an object appearing within manifest (e.g., a Person). The algorithm replaces or adds some terms to manifest; the replacement terms are expressed in JSON syntax as {"term":"value"}.

  1. let lang string represent the default language, set to:

    • the value of the lang value for the script element in document (when set); or
    • undefined otherwise
    Explanation

    This value is used in the step on language below.

  2. let dir string represents the base direction, set to:

    • the value of the dir value for the script element in document (when set); or
    • undefined otherwise
    Explanation

    This value is used in the step on base direction below.

  3. () if manifest["name"] is undefined, locate the title element [html] using document (when set). If that element exists and is non-empty, let t be its text content, and add to manifest:

    • if the language of title is explicitly set to the value of l, then add
      "name": [{"value": t, "language": l}]
    • otherwise
      "name": [t]
    Explanation

    This step adds the content of the title element of document when the name property is not specified in the manifest. For example:

    Example 40 
    <html>
<head>
    <title>Moby Dick</title>
    …
    <script type="application/ld+json">
    {
        "@context" : ["https://schema.org","https://www.w3.org/ns/wp-context"],
        …
    }
    </script>

    yields:

    Example 41 
    {
    "@context" : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "name"     : ["Moby Dick"],
    …
}

  4. () if manifest["inLanguage"] is undefined and the value of lang is not undefined, add
    "inLanguage": lang
    to manifest

    Explanation

    This step ensures that a language explicitly set in document is valid. For example,

    Example 42 
    <html>
<head>
    …
    <script type="application/ld+json" lang=ur>
    {
        "@context" : ["https://schema.org","https://www.w3.org/ns/wp-context"],
        …
    }
    </script>

    yields (unless the language and the direction are set explicitly in the manifest):

    Example 43 
    {
    "@context"    : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "inLanguage"  : "ur",
    …
}

  5. () if manifest["inDirection"] is undefined and the value of dir is not undefined, add
    "inDirection": dir
    to manifest

    Explanation

    This step ensures that the base direction explicitly set in the embedding document is valid. For example,

    Example 44 
    <html>
<head>
    …
    <script type="application/ld+json" dir=rtl lang=ur>
    {
        "@context" : ["https://schema.org","https://www.w3.org/ns/wp-context"],
        "inLanguage"  : "ur",
        …
    }
    </script>

    yields (unless the language and the direction are set explicitly in the manifest):

    Example 45 
    {
    "@context"    : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "inLanguage"  : "ur",
    "inDirection" : "rtl"
    …
}

  6. () if manifest["readingOrder"] is undefined, let u be the value of document.URL, and add
    "readingOrder": [{"type": ["LinkedResource"], "url": u}]
    to the manifest

    Explanation

    If the Digital Publication consists only of the referencing document, the default reading order can be omitted; it will consist, automatically, of that single resource.

  7. () for each value v of P["term"] that is a single string or an object, and where term expects an array: change the relevant term/value pair to
    "term": [v]

    Explanation

    A number of terms require their values to be arrays but, for the sake of convenience, authors are allowed to use a single value instead of a one element array. For example,

    Example 46 
    {
    "@context"  : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "name"      : "Moby Dick",
    "author"    : "Herman Melville",
    "resources" : [{
        "type"           : "LinkedResource",
        "rel"            : "cover",
        "url"            : "images/cover.jpg",
        "encodingFormat" : "image/jpeg"
    },
        …
    }],
    …
}

    yields:

    Example 47 
    {
    "@context"  : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "name"      : ["Moby Dick"],
    "author"    : ["Herman Melville"],
    "resources" : [{
        "type"           : ["LinkedResource"],
        "rel"            : ["cover"],
        "url"            : "images/cover.jpg",
        "encodingFormat" : "image/jpeg"
    },
        …
    }],
    …
}

  8. () for each value v in a manifest["term"] array that is a simple string or a localizable string, and where term expects an entity: exchange that element in the array to
    {"type": ["Person"], "name": [v]}

    Explanation

    An author, editor, etc., should be explicitly designed as an object of type Person but, for the sake of convenience, authors are allowed to just give their name. For example,

    Example 48 
    {
    "@context"  : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "name"      : ["Moby Dick"],
    "author"    : ["Herman Melville"],
    …
}

    yields:

    Example 49 
    {
    "@context"  : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "name"      : ["Moby Dick"],
    "author"    : [{
        "type" : ["Person"],
        "name" : "Herman Melville"
    }],
    …
}

  9. () for each value v in a manifest["term"] array that is a simple string, and where term is one of the resource categorization properties: exchange that element in the array to
    {"type": ["LinkedResource"], "url": v}

    Explanation

    Resource links should be explicitly designed as an object of type LinkedResource but, for the sake of convenience, authors are allowed to just give their absolute or relative URL. For example,

    Example 50 
    {
    "@context"  : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    …
    "resources" : [
        "css/mobydick.css",
        …
    ],
    …
}

    yields:

    Example 51 
    {
    "@context"  : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    …
    "resources" : [{
        "type" : ["LinkedResource"],
        "url"  : "css/mobydick.css"
    },
        …
    ],
    …
}

  10. () for each value v of P["term"], or in P["term"] in the case the latter is an array, that is a simple string, and term expects a localizable string: change the relevant term/value to:

    • if manifest[inLanguage] is set to the value of l then
      "term": {"value": v,"language": l}
    • otherwise
      "term": {"value": v}
    Explanation

    Natural language text values should be explicitly designed as localizable string objects but, for the sake of convenience, authors are allowed to just use a simple string. I.e., if no language information has been provided (via inLanguage) in the manifest then, for example,

    Example 52 
    {
    "@context"  : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "name"      : ["Moby Dick"],
    "author"    : ["Herman Melville"],
    …
}

    yields:

    Example 53 
    {
    "@context"  : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "name"      : [{
        "value" : "Moby Dick"
    }],
    "author"    : [{
        "value" : "Herman Melville"
    }],
    …
}

    If an explicit language has also been provided in the manifest, that language is also added to the localizable string object. For example,

    Example 54 
    {
    "@context"   : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "inLanguage" : "en",
    "name"       : ["Moby Dick"],
    "author"     : ["Herman Melville"],
    …
}

    yields:

    Example 55 
    {
    "@context"  : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "inLanguage": "en",
    "name"      : [{
        "value"    : "Moby Dick",
        "language" : "en"
    }],
    "author"    : [{
        "value"    : "Herman Melville"
        "language" : "en"
    }],
    …
}

  11. () for each value v of P["term"] that is not an absolute URL string, and where term expects a URL: resolve this value, considered to be a relative URL, using the value of base and yielding the value of au, and replace the term/value pair by
    "term": au

    Explanation

    All relative URLs in the Publication Manifest must be resolved against the base value to yield absolute URLs.

  12. (, extension point) if a profile defines its own canonicalization steps for profile specific terms, those steps are executed at this point.

  13. Return the (transformed) manifest.

See the diagram in the appendix for a visual representation of the algorithm. Also, to help understanding the result of the algorithm, there is a link to the corresponding canonical manifests for all the examples in .

Post-Processing a Canonical Manifest

The steps for post-processing a canonical manifest are given by the following algorithm. The algorithm takes a json object representing a canonical manifest. The output from inputting a JSON object into this algorithm is a processed manifest. The goal of the algorithm is to ensure that the data represented in json abides to the minimal requirements on the data, removing, if applicable, non-conformant data.

As an abuse of notation, P["term"] refers to the value in the object P for the label "term", where P is either manifest, or an object appearing within manifest (e.g., a LinkedResource).

  1. Let manifest be the result of converting json to a PublicationManifest dictionary.

  2. Perform data cleanup operations on manifest, possibly removing data, as well as raising warnings.

    1. For all term that expect entities, check whether the value object P in manifest[term] has P["name"] set. If not, remove P from manifest[term] array and issue a warning.
    2. For all term defined in , check whether every object P in manifest[term] has P["url"] set. If not, remove P from manifest[term] array and issue a warning. If yes, check whether P["url"] is a valid URL [url] and, if not, issue a warning.
    3. For every object P of type LinkedResource, if the value of P["length"] is set, check whether this value is a valid number. If the check fails, issue a warning.
    4. Check whether the value of manifest["name"] is not empty. If it is, generate a value (see the separate note for details) and issue a warning.
    5. Check whether manifest["datePublished"] is a valid date or date-time, per [iso8601]. If the check fails, issue a warning.
    6. Check whether manifest["dateModified"] is a valid date or date-time, per [iso8601]. If the check fails, issue a warning.
    7. Check whether manifest["duration"] is a valid duration value, per [iso8601]. If the check fails, issue a warning.

  3. Extension point: process any proprietary, profile specific, and/or other supported members at this point in the algorithm.

  4. Return manifest.

PART II: Web Publications

Introduction

A Web Publication is a discoverable and identifiable collection of resources. Information about the Web Publication is expressed in its manifest, which is an implementation of the format defined in . The manifest is what enables user agents to understand the bounds of the Web Publication and the connection between its resources.

The manifest includes metadata that describe the Web Publication, as a publication has an identity and nature beyond its constituent resources. The manifest also provides a list of all the resources that belong to the Web Publication and a default reading order, which is how it connects resources into a single contiguous work.

A Web Publication is discoverable via the presence of a link to the manifest in any of its resources (i.e., by the use of an HTTP Link header or an HTML link element [html]). The linked manifest is contained either directly within the resource containing the link (in a special case called the primary entry page) or in a separate JSON-LD document.

With the establishment of Web Publications, user agents can build new experiences tailored specifically for their unique reading needs.

Flowchart depicts the resources of a Web Publication and their attachment to a manifest.
Simplified Diagram of the Structure of Web Publications.
A description of the structure diagram is available in the Appendix. Image available in SVG and PNG formats.

Conformance Classes

This specification defines two conformance classes: one for Web Publications and one for user agents that process them.

A Web Publication conforms to this specification if it meets the following criteria:

A user agent conforms to this specification if it meets the following criteria:

Web Publication Construction

Publication Bounds

A Web Publication consists of a finite set of resources that represent its content. This extent is known as its bounds and is defined within its manifest — it is obtained from the union of resources listed in the default reading order and resource list.

To determine whether a resource is within the bounds of a Web Publication, user agents MUST compare the absolute URL of a resource to the absolute URLs of the resources obtained from the union. If the resource is identified in the enumeration, it is within the bounds of the Web Publication. All other resources are external to the Web Publication.

Resources within the bounds of a Web Publication do not have to share the same domain.

Resources

A Web Publication MUST include at least one HTML document [html]—the primary entry page.

Otherwise, a Web Publication MAY references resources of any media type, both in the default reading order and as dependencies of other resources.

When adding resources to a Web Publication, consider support in user agents. The use of progressive enhancement techniques and the provision of fallback content, as appropriate, will ensure a more consistent reading experience for users regardless of their preferred user agent.

Primary Entry Page

The primary entry page represents the preferred starting resource for a Web Publication and enables discovery of its manifest. It is an [HTML] resource that is returned when accessing the Web Publication's address, and MUST be included in either the default reading order or the resource list.

Although any resource can link to the manifest, the primary entry page typically introduces the Web Publication and provides access to the content. It might contain all the content, in the case of a single-page Web Publication, or provide navigational aids to begin reading a multi-document Web Publication. To facilitate the user ease of consumption, the primary entry page SHOULD contain the table of contents.

It is not required that the primary entry page be included in the default reading order, nor that it be the first document listed when it is included. This specification leaves the exact nature of the document intentionally underspecified to provide flexibility for different approaches. If a default reading order is not provided, however, user agents will create one using the primary entry page.

The address of the primary entry page is also the canonical identifier for the Web Publication (i.e., it serves as its unique identifier).

In certain cases where information has been omitted from the manifest, user agents will sometimes use the primary entry page as a fallback source of information (see language and base direction and title).

Table of Contents

The table of contents provides a hierarchical list of links that reflects the structural outline of the major sections of the Web Publication.

The table of contents is expressed via an [html] element (typically a nav element) in one of the resources. This element MUST be identified by the role attribute [html] value "doc-toc" [dpub-aria-1.0], and MUST be the first element in the document — in document tree order [dom] — with that role value.

If the table of contents is not located in the primary entry page, the manifest SHOULD identify the resource that contains the structure.

Example 56: If the primary entry page includes the table of contents, no reference to it in the manifest is necessary 
<head>
    …
    <script type="application/ld+json">
    {
        "@context"        : ["https://schema.org","https://www.w3.org/ns/wp-context"],
        "type"            : "TechArticle",
        …
        "id"              : "http://www.w3.org/TR/tabular-data-model/",
        "url"             : "http://www.w3.org/TR/2015/REC-tabular-data-model-20151217/",
        …
    }
    </script>
    …
</head>
<body>
    …
    <section role="doc-toc">
        …
    </section>
    …
</body>

When specified, the table of content MUST include a link to at least one resource, and all links SHOULD refer to resources within publication bounds.

Refer to the table of contents property definition for more information on how to identify which resource contains the table of contents.

Page List

The page list is a list of links that provides navigation to static page demarcation points within the content. These locations allow users to coordinate access into the content, but the exact nature of the locations is left to content creators to define. They usually correspond to pages of a print document which is the source of the Web Publication, but might be a purely digital creation added to ease navigation.

The page list is expressed via an [html] element (typically a nav element) in one of the resources. This element MUST be identified by the role attribute [html] value "doc-pagelist" [dpub-aria-1.0], and MUST be the first element in the document — in document tree order [dom] — with that role value.

If the page list is not located in the primary entry page, the manifest SHOULD identify the resource that contains the structure.

There are no requirements on the page list itself, except that, when specified, it MUST include a link to at least one resource.

Refer to the pagelist property definition for more information on how to identify which resource contains the page list.

Manifest

Requirements

The expression of properties in a Web Publication manifest includes a combination of those defined generally for digital publications as well as two specific to Web Publications: the publication's address and canonical identifier.

The requirements for the expression of these properties are as follows:

REQUIRED:
RECOMMENDED:

These properties do not all have to be serialized in the authored manifest. Refer to each property's definition to determine whether it is required in the manifest or can be compiled into the canonical manifest from other information.

In addition, inclusion of the following resources is RECOMMENDED:

Properties

Default Reading Order

The Web Publication readingOrder property extends the Publication Manifest readingOrder property in the following ways:

  • The default reading order MAY be omitted when it only consists of the primary entry page. When the default reading order is absent, user agents MUST include an entry for the primary entry page when compiling the canonical manifest.
Title

The Web Publication title property extends the Publication Manifest title property in the following ways:

Relying on the title element could be semantically problematic if the Web Publication consists of several HTML resources (e.g., one per chapter of a book), because the HTML definition defines this element as "metadata" for the enclosing HTML document, not for a collection of resources. Using this element is, on the other hand, preferred in the case of a Web Publication consisting of a single HTML document (e.g., a scholarly journal article).

Association

Manifest

The primary entry page MUST provide a link to the manifest to enable its discovery. It is the only resource that can provide this link.

The primary entry page is also the only resource in which a manifest can be embedded. It is RECOMMENDED to embed the manifest in the primary entry page, but the manifest MAY be external to it.

Embedding is the preferred option as search engines might only process schema.org metadata in JSON-LD format when it is embedded in an HTML page.

Publication

A link to the primary entry page MAY be included in any resource to establish that it belongs to a Web Publication.

Need to determine what relation to use for linking.

Linking resources to their Web Publication is encouraged whenever possible, as it allows user agents to ascertain that a resource belongs to a Web Publication regardless of how the user reaches the resource.

The resources of a Web Publication MUST NOT link directly to the manifest; only the primary entry page is permitted to provide such a link.

Web Publication Lifecycle

The processing of the Web Publication manifest extends the lifecycle defined in as described in this section.

See the diagrams in the appendix for a visual representation of the lifecycle algorithm.

Obtaining a manifest

The steps for obtaining a manifest, starting from the primary entry page, are given by the following algorithm.

  1. If the primary entry page does not have the media type text/html or application/xhtml+xml, terminate this algorithm.
  2. From the Document of the top-level browsing context of the primary entry page, let origin be the Document's origin, and manifest link be the first link element in tree order in Document whose rel attribute contains the publication token.
  3. If origin is an [html] opaque origin, terminate this algorithm.
  4. If manifest link is null, terminate this algorithm.
  5. If manifest link's href attribute's value is the empty string, terminate this algorithm.

  6. If the href attribute value of manifest link is equivalent to [URL] origin:

    1. If it has a non-null fragment identifying an identifier id in Document:

      1. Let embedded manifest script be the first script element in tree order, whose id attribute is equal to id and whose type attribute is equal to application/ld+json.
      2. If embedded manifest script is null, terminate this algorithm.
      3. Let text be the child text content of embedded manifest script
      4. Let base be the value of baseURI of the script element.
    2. Otherwise, terminate this algorithm.
    Explanation

    This branch is in use when the manifest is embedded in the primary entry page. The algorithm locates the script element and extract the manifest itself. The document's URL or, if set by the author, the value of a possible base element will be used to turn relative URLs into absolute ones.

  7. Otherwise:
    1. Let manifest URL be the result of parsing the value of the href attribute, relative to the element's base URL. If parsing fails, then abort these steps.
    2. Let request be a new [fetch] request, whose URL is manifest URL, and whose context is the same as the browsing context of the Document.
    3. If the manifest link's crossOrigin attribute's value is 'use-credentials', then set request's credentials to 'include'.
    4. Await the result of performing a fetch with request, letting response be the result.
    5. If response is a network error, terminate this algorithm.
    6. Let text be the result of UTF-8 decoding response's body.
    7. Let base be the value of manifest URL.
    Explanation

    This branch is in use when the manifest is in a separate file. It performs the standard operations to retrieve the manifest from the Web; the URL of the manifest file will be used to turn relative URLs into absolute ones.

If text contains a non-empty string, it is the input to the first step in the processing stage, with base as the base URL, and Document as the primary entry page. Otherwise, terminate this algorithm.

Processing a Manifest

The processing of a Web Publication adds the following requirement to the minimal canonical manifest requirements step:

  • if the address is not equivalent to [URL] the URL of document, terminate the algorithm.

Extracting a Table of Contents

If a user agent requires the table of contents, it MUST compute the table of contents as follows:

  1. Identify the table of contents resource:
  2. If the table of contents resource contains an HTML element with the role [html] value doc-toc [dpub-aria-1.0], the user agent MUST use that element as the table of contents. If there are several such HTML elements the user agent MUST use the first in document tree order [dom].

See the separate section for the HTML structure that the table of content SHOULD adhere to.

There is no fixed time in the manifest lifecycle when processing of the table of contents has to occur, only that it cannot occur before generating the canonical manifest.

Example 57: Table of content identified in another resource of the publication 
{
    "@context"   : ["https://schema.org","https://www.w3.org/ns/wp-context"],
    "type"       : "Book",
    …
    "url"        : "https://publisher.example.org/mobydick",
    "name"       : "Moby Dick",
    "resources"  : [{
        "type"       : "LinkedResource",
        "url"        : "toc_file.html",
        "rel"        : "contents"
    },{
        …
    }],
    …
}
Example 58: If the primary entry page includes the TOC, no reference in the manifest is necessary 
<head>
    …
    <script type="application/ld+json">
    {
        "@context"        : ["https://schema.org","https://www.w3.org/ns/wp-context"],
        "type"            : "TechArticle",
        …
        "id"              : "http://www.w3.org/TR/tabular-data-model/",
        "url"             : "http://www.w3.org/TR/2015/REC-tabular-data-model-20151217/",
        …
    }
    </script>
    …
</head>
<body>
    …
    <section role="doc-toc">
        …
    </section>
    …
</body>

Extracting a Page List

User agents MUST compute the page list as follows:

  1. Identify the page list resource:
  2. If the page list resource contains an HTML element with the role [html] value doc-pagelist [dpub-aria-1.0], the user agent MUST use that element as the page list. If there are several such HTML elements the user agent MUST use the first in document tree order [dom].

The Working Group will attempt to define the pagelist term with IANA, to avoid using a URL.

There is no fixed time in the manifest lifecycle when processing of the page list has to occur, only that it cannot occur before generating the canonical manifest.

Example 59: Page list identified in another resource of the publication 
{
"@context"   : ["https://schema.org","https://www.w3.org/ns/wp-context"],
"type"       : "Book",
…
"url"        : "https://publisher.example.org/mobydick",
"name"       : "Moby Dick",
"resources"  : [{
	"type"       : "LinkedResource",
	"url"        : "toc_file.html",
	"rel"        : "pagelist"
},{
	…
}],
…
}

Security

Placeholder for security issues.

Privacy

Placeholder for privacy issues.

PART III: Modular Extensions

Introduction

The first two parts of this specification define the cornerstones for developing additional digital publication formats that can be deployed to the Web. Various publishing communities (e.g., audio books, scholarly publications) MAY define extensions, also known as profiles, by extending the core with module specific terms and possibly adding new requirements.

Compatibility Requirements

In order for a digital publication format to be compatible with this specification, following conditions MUST be met:

Adding an example of a term added by, e.g., the audiobook profile would be a good idea, when available.

LinkedResource Definition
Term Description Required Value Value Type [schema.org] Mapping
url Location of the resource. REQUIRED. A valid URL string [url]. Refer to the property definitions that accept this type for additional restrictions. URL url
encodingFormat Media type of the resource (e.g., text/html). OPTIONAL. MIME Media Type [rfc2046]. Literal encodingFormat
name Name of the item. OPTIONAL. One or more Text items. Array of Localizable Strings name
description Description of the item. OPTIONAL. Text. Localizable String description
rel The relation of the resource to the publication. OPTIONAL.

One or more relations. The values are either the relevant relation terms of the IANA link registry [iana-link-relations], or specially-defined URLs if no suitable link registry item exists.

 Array of Literals (None)
integrity A cryptographic hashing of the resource that allows its integrity to be verified. OPTIONAL.

One or more whitespace-separated sets of integrity metadata [sri]. The value MUST conform to the metadata definition [sri].

Refer to [sri] for the list of cryptographic hashing functions that user agents are expected to support.

 Literal (None)
length The total length of a time-based media resource in (possibly fractional) seconds. OPTIONAL Number Number (None)

Although user agent support for the integrity property is OPTIONAL, user agents that support cryptographic hashing comparisons using this property MUST do so in accordance with [sri].

dictionary LinkedResource {
    required DOMString           url;
             DOMString           encodingFormat;
             sequence<LocalizableString>   name;
             LocalizableString   description;
             sequence<DOMString> rel;
             DOMString           integrity;
             double              length;
};

Machine-Processable Table of Contents

Introduction

To facilitate navigation within pages and across sites, HTML uses the nav element [html] to express lists of links. Although generic in nature by default, the purpose of a nav element can be more specifically identified by use of the role attribute [html]. In particular, the doc-toc role from the [dpub-aria-1.0] vocabulary identifies the nav element as the Web Publications's table of contents.

Including an identifiable table of contents is an accessible way to produce any digital publication, but due to the flexibility of HTML markup, it also presents challenges for user agents trying to extract a meaningful hierarchy of links (e.g., to provide a custom view available from any page). To avoid duplicating the tables of contents for different uses, this section defines a syntax that is both human friendly and commonly used while still providing enough structure for user agent extraction.

Authors have a choice of lists (ordered or unordered) to construct their table of contents. By tagging each link within these lists in anchor tags (a elements), user agents can easily differentiate the information they need from any peripheral content (asides) or stylistic tagging that has also been added. The table of contents can consist of both active links (with an href attribute) and inactive links (excluding the href attribute), providing additional flexibility in how the table of contents is constructed (e.g., to omit links to certain headings or only link to certain content in a preview).

HTML Structure

The machine-readable table of contents is defined within an [html] nav element. As described in , this nav element has to be both the first element in the document and identifiable by a role attribute with the value doc-toc.

Although the content model of the nav element is not restricted, user agents will only be able to extract a usable table of contents when the following markup guidelines are followed:

Table of Contents Title

Although a title for the table of contents is optional, to avoid having a user agent generate a placeholder title when one is needed, it is advised to add one. Titles are specified using any of the [html] h1 through h6 elements. Note that only the first such element is recognized as the title. If a heading element is not found before the list of links, user agents will assume that one has not been specified.

The first [html] ol or ul list element encountered in the nav element is assumed to contain the list that defines the links into the content. This list will be found even if it is nested inside of div elements, for example, as the algorithm ignores elements that are not relevant to its processing. The list cannot occur inside of any skipped elements, however, since their internal contents are not evaluated.

If the nav element does not contain one of these elements, then user agents will not register the digital publication as containing a usable table of contents (e.g., a machine-rendered option will not be available).

Branches

If the table of contents is considered as a tree of links, then each list item (li element) inside of the list of links represents one branch. Each of these branches has to have a name and optional destination in order to be presented to users, and this information is obtained from the first a element found within the list item, wherever it is nested (again, excluding any a elements inside of skipped elements.)

The link destination for the branch is obtained from the a element's href attribute, when specified. This attribute can be omitted if a link is not available (e.g., in a preview) or not relevant (e.g., a grouping header). When providing a link into the content, it is also possible to specify the relation of the linked document (in a rel attribute) and the media type of the linked resource (in a type attribute).

After finding the a element that labels the branch, user agents will continue to inspect the markup for another list element (i.e., sub-branches). If a list is found, it is similarly processed to extract its links, and so on, until there are no more nested branches left to process.

Skipped Elements

A small set of elements are ignored when the parsing table of contents to avoid misinterpretation. These are the [html] sectioning content elements and sectioning root elements. The reason they are ignored is because they can defined their own outlines (i.e., they can represent embedded content that is self-contained and not necessarily related to the structure of content links).

Any element that has its hidden attribute set is also skipped, since hidden elements are not intended to be directly accessed by users.

Although these elements can be included in the nav element, care has to be taken not to embed important content within them (e.g., do not wrap a section element around the list item that contains all the links into the content).

Ignored Elements

All elements that are not relevant to extracting the table of contents, and are not skipped, are ignored. Unlike skipped elements, ignoring means that user agents will continue to search inside them for relevant content, allowing greater flexibility in terms of the tagging that can be used.

Examples

User Agent Processing

This section defines an algorithm for extracting a table of contents from a nav element. It is defined in terms of a walk over the nodes of a DOM tree, in tree order, with each node being visited when it is entered and when it is exited during the walk. Each time a node is visited, it can be seen as triggering an enter or exit event. In some steps, user agents are provided a choice in how to process the content to provide flexibility for different presentation models.

For illustrative purposes, the examples in this section show the structure of the table of contents as JavaScript objects. User agents can process and internalize the resulting structure in whatever language and form is appropriate.

For the purposes of this algorithm, a list element is defined as either an [html] ol or ul element.

The following algorithm MUST be applied to a walk of a DOM subtree rooted at the first nav element in document order with the role attribute value doc-toc. All explanations are informative.

  1. Let toc be a object that represents the table of contents and initialize it as follows:

    1. Create a name property for toc that represents the title of the table of contents and set to an empty string.
    2. Create an entries property for toc that represents all the branches of the table of contents and set to an empty array.
    Explanation

    This step initializes the toc object that will store the title and the branches of the table of contents.

  2. Initialize a stack.

    Explanation

    The stack is used to hold branches that are not yet complete. As a new sub-branch is encountered, the parent gets pushed onto the stack so it can be retrieved later.

  3. Let current toc branch be a variable set to null.

    Explanation

    current toc branch is used to hold the object that represents the branch of the table of contents that is currently being processed.

  4. Walk over the DOM in tree order, starting with the nav element the table of contents is being built from, and trigger the first relevant step below for each element as the walk enters and exits it.

    1. When entering a heading content element:

      Run these steps:

      1. If the stack is empty, and the name property of toc is an empty string, set the name property to one of the following:

        • the descendant content of the element (to preserve any HTML tags);
        • the text string obtained from the descendant content (e.g., by calculating the accessible name [accname-1.1] of the element).

        If the resulting value of name is an empty string (e.g., after removing any presentational elements and trimming all leading and trailing whitespace), set the name property either to a placeholder value or to null.

      2. Exit the element and continue processing with the next element.
      Explanation

      This step identifies the heading for the table of contents. A heading is only processed if the value of the toc name property is an empty string (i.e., no headings have yet been encountered).

      Whether a user agent sets the name to the descendant content of the heading element, or generates a text string from it, depends on whether it will re-use any descendant tagging in the presentation (e.g., to retain images, MathML, ruby and other content that does not translate to text easily).

      If the name is not an empty string, or is null, then a previous heading has already been encountered or content has been encountered that indicates the nav element does not have a heading (e.g., a list has already been processed, since the heading would not follow the list of links).

    2. When entering a list element:

      Run these steps:

      1. If the name property of toc is an empty string, set name to null.

      2. If current toc branch is not null:

        1. If the entries property of current toc branch is null or a non-empty array, exit the element and continue processing with the next element.
        2. Otherwise, push the object in current toc branch onto the stack and set current toc branch to null.

      3. Otherwise, if the stack is empty:

        1. If the entries property of toc is null or a non-empty array, exit the element and continue processing with the next element.
        2. Otherwise, do nothing.
      Explanation

      This algorithm does not process multiple lists in a single branch or at the root of the nav element, so if a list has already been encountered (the entries property contains one or more branches or is set to null), this list is skipped.

      If a list is encountered and the table of contents (toc) still does not have a name (i.e., no heading element has been encountered), the table of contents is assumed to not have a heading (i.e., the heading for the table of contents cannot appear after the first list of entries). The value of the name property is changed from an empty string to null as no further headings encountered apply, either.

    3. When exiting a list element:

      If the stack is not empty, pop the top object off the stack and set current toc branch to it.

      Explanation

      This resets current toc branch back to the parent object after all of its child branches have been processed.

    4. When entering a list item element:

      Run these steps:

      1. Set current toc branch to a new object.
      2. Create name, url, type, and rel properties for the object and set them to empty strings.
      3. Create an entries property for the object and set it to an empty array.
      Explanation

      Each list item represents a possible new branch in the table of contents, so whenever one is encountered a new blank object is created in current toc branch.

      This object gets populated with information as a descendant a element and list are encountered.

    5. When exiting a list item element:

      Run these steps:

      1. If entries property of current toc branch contains an empty array, set its value to null.

      2. If the stack contains one or more entries:

        1. If the entries property of current toc branch contains a non-empty array, and its name property is an empty string, set its name to a placeholder value or null;
        2. If the entries property of current toc branch contains an empty array, and its name property is an empty string, set current toc branch to null and exit this processing step.

        Add current toc branch to the array in the entries property of the object at the top of the stack.

      3. Otherwise, add the object in current toc branch to the entries array of toc.

      4. Set current toc branch to null.

      Explanation

      Exiting a list item indicates that processing of the current branch is complete. Before adding this branch to its parent's entries array, the branch needs to be tested to see if it has a name and/or any sub-branches. If it does not have a name but has sub-branches, the branch is kept. The user agent can either supply a placeholder value of its own creation or set the value to null. If it does not have a name or any branches, it is invalid and is discarded.

      To determine where to merge the branch, the stack is checked. If there are no objects in the stack, it is added into the entries property of the root toc object (i.e., it is a top-level branch). Otherwise, it gets added into the entries property of the object immediately preceding it in the stack.

      As a final step, current toc branch is reset back to null.

    6. When entering an anchor element and current toc branch is not null:

      Run these steps:

      1. If the name property of current toc branch is not an empty string, do nothing.

      2. Otherwise:

        1. Set the name property of current toc branch to one of the following:

          • the descendant content of the anchor element (to preserve any HTML tags);
          • the text string obtained from the descendant content (e.g., by calculating the accessible name [accname-1.1] of the element).

          If the resulting value of name is an empty string (e.g., after removing any presentational elements and trimming all leading and trailing whitespace), set the name property to null.

        2. If the element has an href attribute and the URL in the attribute resolves to a resource in the default reading order or resource list, set the url property of current toc branch to the value. Otherwise, set the property to null.
        3. If the element has a type attribute, and the value of the attribute is not an empty string after trimming leading and trailing white space, set the type property of current toc branch to its value. Otherwise, set the property to null.
        4. If the element has a rel attribute, and the value of the attribute is not an empty string after trimming leading and trailing white space, set the rel property of current toc branch to its value. Otherwise, set the property to null.

        Exit the element and continue processing with the next element.

      Explanation

      This step processes anchor tags to obtain values for the name and url properties of a branch.

      If the name of the current branch is already defined, then processing of this element is terminated (i.e., to avoid processing multiple links for a single branch).

      Whether a user agent sets the name of the entry to the descendant content of the a element, or generates a text string from it, depends on whether it will re-use any descendant tagging in the presentation (e.g., to retain images, MathML, ruby and other content that does not translate to text easily).

      In addition to having an href attribute specified, it is necessary that it resolve to a resource that belongs to the digital publication to meet the requirements of this specification. If not, the branch is retained but the entry will not be linkable.

      Additional information about the target of the link — the type of resource and its relation — is also retained.

    7. When entering a sectioning content element, a sectioning root element, or an element with a hidden attribute:

      Exit the element and continue processing with the next element.

      Explanation

      As sectioning and sectioning root elements can define their own outlines, descending into them poses problems for generating the table of contents (i.e., they may contain content that is not directly related). As a result, they are skipped over when encountered to prevent their child content from being processed.

    8. Otherwise: do nothing.

      Explanation

      For all other elements, this steps allows their descendant elements to continue to be processed.

  5. After completing the DOM walk, if the entries property of toc contains a non-empty array, toc represents the machine-processed table of contents.

    Otherwise, the digital publication does not have a table of contents that can be used for machine rendering purposes.

    Explanation

    If the entries array in the root toc object does not contain any branches (either because no list was found in the nav element or the list did not contain any conforming list items), then the algorithm did not produce a usable table of contents.

Manifest Examples

Simple Book

A manifest for a simple book. The canonical version of this manifest is also available.

Example 71 
{
    "@context": ["https://schema.org", "https://www.w3.org/ns/wp-context"],
    "type": "Book",
    "url": "https://publisher.example.org/mobydick",
    "author": "Herman Melville",
    "dateModified": "2018-02-10T17:00:00Z",

    "readingOrder": [
        "html/title.html",
        "html/copyright.html",
        "html/introduction.html",
        "html/epigraph.html",
        "html/c001.html",
        "html/c002.html",
        "html/c003.html",
        "html/c004.html",
        "html/c005.html",
        "html/c006.html"
    ],

    "resources": [
        "css/mobydick.css",
        {
            "type": "LinkedResource",
            "rel": "cover",
            "url": "images/cover.jpg",
            "encodingFormat": "image/jpeg"
        },{
            "type": "LinkedResource",
            "url": "html/toc.html",
            "rel": "contents"
        },{
            "type": "LinkedResource",
            "url": "fonts/STIXGeneral.otf",
            "encodingFormat": "application/vnd.ms-opentype"
        },{
            "type": "LinkedResource",
            "url": "fonts/STIXGeneralBol.otf",
            "encodingFormat": "application/vnd.ms-opentype"
        },{
            "type": "LinkedResource",
            "url": "fonts/STIXGeneralBolIta.otf",
            "encodingFormat": "application/vnd.ms-opentype"
        },{
            "type": "LinkedResource",
            "url": "fonts/STIXGeneralItalic.otf",
            "encodingFormat": "application/vnd.ms-opentype"
        }
    ]
}

Single-Document Publication

Example for an embedded manifest example. The canonical version of the manifest is, as well as a more elaborate version for the same document are also available.

Example 72 
<!DOCTYPE html>
<html lang="en-US">
<head>
    <title>Model for Tabular Data and Metadata on the Web</title>
    <link href="#wpm" rel="publication" />
    ...
    <script id="wpm" type="application/ld+json">
    {
        "@context"        : ["https://schema.org", "https://www.w3.org/ns/wp-context"],
        "type"            : "TechArticle",
        "id"              : "http://www.w3.org/TR/tabular-data-model/",
        "url"             : "http://www.w3.org/TR/2015/REC-tabular-data-model-20151217/",
        "copyrightYear"   : "2015",
        "copyrightHolder" : "World Wide Web Consortium",    
        "creator"         : ["Jeni Tennison", "Gregg Kellogg", "Ivan Herman"],
        "publisher" : {
            "type" : "Organization",
            "name" : "World Wide Web Consortium",
            "id"   : "https://www.w3.org/"
        },
        "datePublished"         : "2015-12-17",
        "resources"             : [
            "datatypes.html",
            "datatypes.svg",
            "datatypes.png",
            "diff.html",
            {
                "type"           : "LinkedResource",
                "url"            : "test-utf8.csv",
                "encodingFormat" : "text/csv"

            },
            {
                "type"           : "LinkedResource",
                "url"            : "test.xlsx",
                "encodingFormat" : "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
            }
        ],
    }
    </script>
</head>
<body>
    ....

    <section id="toc" role="doc-toc">
        <h2 resource="#h-toc" id="h-toc" class="introductory">Table of Contents</h2>
        <ul class="toc">
            <li class="tocline"><a class="tocxref" href="#intro">
                <span class="secno">1. </span>Introduction</a>
            </li>
            ...
        </ul>
    </section>
    ...

</body>
</html>

Audiobook

A manifest for an audiobook. The canonical version of this manifest is also available.

Example 73 
{
  "@context": ["https://schema.org", "https://www.w3.org/ns/wp-context"],
  "type": "Audiobook",
  "id": "https://librivox.org/flatland-a-romance-of-many-dimensions-by-edwin-abbott-abbott/",
  "url": "https://w3c.github.io/wpub/experiments/audiobook/",
  "name": "Flatland: A Romance of Many Dimensions",
  "author": "Edwin Abbott Abbott",
  "readBy": "Ruth Golding",
  "publisher": "Librivox",
  "inLanguage": "en",
  "dateModified": "2018-06-14T19:32:18Z",
  "datePublished": "2008-10-12",
  "duration": "PT15153S",
  "license": "https://creativecommons.org/publicdomain/zero/1.0/",

  "resources": [
    {
      "rel": "cover",
      "url": "http://ia800704.us.archive.org/9/items/LibrivoxCdCoverArt12/Flatland_1109.jpg",
      "encodingFormat": "image/jpeg"
    },{
      "rel": "contents", 
      "url": "toc.html", 
      "encodingFormat": "text/html"
    }
  ],

  "readingOrder": [
    {
      "url": "http://www.archive.org/download/flatland_rg_librivox/flatland_1_abbott.mp3",
      "encodingFormat": "audio/mpeg",
      "length": 1371,
      "name": "Part 1, Sections 1 - 3"
    },{
      "url": "http://www.archive.org/download/flatland_rg_librivox/flatland_2_abbott.mp3",
      "encodingFormat": "audio/mpeg", 
      "length": 1669,
      "name": "Part 1, Sections 4 - 5"
    },{
      "url": "http://www.archive.org/download/flatland_rg_librivox/flatland_3_abbott.mp3",
      "encodingFormat": "audio/mpeg",
      "length": 1506,
      "name": "Part 1, Sections 6 - 7"
    },{
      "url": "http://www.archive.org/download/flatland_rg_librivox/flatland_4_abbott.mp3",
      "encodingFormat": "audio/mpeg",
      "length": 1669,
      "name": "Part 1, Sections 8 - 10"
    },{
      "url": "http://www.archive.org/download/flatland_rg_librivox/flatland_5_abbott.mp3",
      "encodingFormat": "audio/mpeg",
      "length": 1506,
      "name": "Part 1, Sections 11 - 12"
    },{
      "url": "http://www.archive.org/download/flatland_rg_librivox/flatland_6_abbott.mp3",
      "encodingFormat": "audio/mpeg",
      "length": 1798,
      "name": "Part 2, Sections 13 - 14"
    },{
      "url": "http://www.archive.org/download/flatland_rg_librivox/flatland_7_abbott.mp3",
      "encodingFormat": "audio/mpeg",
      "length": 1225,
      "name": "Part 2, Sections 15 - 17"
    },{
      "url": "http://www.archive.org/download/flatland_rg_librivox/flatland_8_abbott.mp3",
      "encodingFormat": "audio/mpeg",
      "length": 1371,
      "name": "Part 2, Sections 18 - 20"
    },{
      "url": "http://www.archive.org/download/flatland_rg_librivox/flatland_9_abbott.mp3", 
      "encodingFormat": "audio/mpeg",
      "length": 1659,
      "name": "Part 2, Sections 21 - 22"
    }
  ]
}

Examples for bidirectional texts

This section illustrates how Unicode formatting characters can be applied to bidirectional strings, where necessary, in order to help a consumer produce the expected display. In cases where the first-strong heuristics would produce the wrong result, if the string is created with a prepended formatting character, the first-strong heuristics will produce the correct base direction for the string as a whole.

A right-to-left string that begins with a Latin script character should have U+200F RIGHT-TO-LEFT MARK prepended.

Character order in memory:  HTML היא שפת סימון.
Gives incorrect display:  HTML היא שפת סימון.
Source code with formatting character:  "\u200FHTML היא שפת סימון."
Gives expected display:  HTML היא שפת סימון.

A left-to-right string that begins with a Arabic script character should have U+200E LEFT-TO-RIGHT MARK prepended.

Character order in memory:  'سلام' is hello in Persian.
Gives incorrect display:  'سلام' is hello in Persian.
Source code with formatting character:  "\u200E'سلام' is hello in Persian."
Gives expected display:  'سلام' is hello in Persian.

Lifecycle diagrams

These diagrams provide a visual view of the lifecycle steps, as specified in .

Overview of the lifecyle algorithm

Overview of the lifecyle algorithm, depicting the main building blocks
Overview of the lifecyle algorithm, depicting the main building blocks.
See the normative description of the algorithm in . Image available in SVG and PNG formats.

Finding the manifest

First major block in the lifecyle algorithm: find the manifest, either through an HTTP request or as part of a script elements
First major block in the lifecyle algorithm: find the manifest, either through an HTTP request or as part of a script elements.
See the normative description of the algorithm in . Image available in SVG and PNG formats.

Manifest canonicalization

Second major block in the lifecyle algorithm: create a canonical manifest (using the core manifest terms as examples)
Second major block in the lifecyle algorithm: create a canonical manifest (using the core manifest terms as examples).
See the normative description of the algorithm in . Image available in SVG and PNG formats.

Converting the manifest into a data structure

Third major block in the lifecyle algorithm: convert the manifest into a programming language dependent data structure that implements the Web IDL specification of the manifest.
Third major block in the lifecyle algorithm: convert the manifest into a programming language dependent data structure that implements the Web IDL specification of the manifest.
See the normative description of the algorithm in . Image available in SVG and PNG formats.

Cleaning up the data

Fourth major block in the lifecyle algorithm: check and clean up data by possibly removing data that cannot be interpreted.
Fourth major block in the lifecyle algorithm: check and clean up data by possibly removing data that cannot be interpreted.
See the normative description of the algorithm in . Image available in SVG and PNG formats.

Properties Index

The following table identifies where the use of manifest properties is defined and extended.

Name Publication Manifest Web Publication
accessMode
accessModeSufficient
accessibilityFeature
accessibilityHazard
accessibilitySummary
address
artist
author
contributor
creator
dateModified
datePublished
duration
editor
id
illustrator
inDirection
inker
inLanguage
letterer
link
name Extended in
penciler
publisher
readBy
readingOrder Extended in
readingProgression
resources
translator

Resource Relations Index

The following table identifies where the use of resource relations is defined.

Name Publication Manifest
accessibility-report
contents
cover
pagelist
privacy-policy
preview

Image Descriptions

Description for the "Structure of Web Publications" diagram:
A simplified diagram of the structure of a Web Publication. The Web Publication is broken down into two elements. The first element is the actual contents (all the real things listed in the manifest). This element is broken down into the CSS, the actual "things" such as the HTML documents, audio, etc, and the images, fonts etc. The actual "things" have an additional subset of items that includes the entry page to the publication and all of the other documents. The second element is the Manifest (JSON). The manifest is used to generate the canonical manifest, which consists of a list of all the "things" in the publication, the publication metadata, and the default reading order of content. It is noted in the diagram that the entry page has to link to the manifest. (Return to the diagram of Web Publication.)

Acknowledgements

The editors would like to thank the members of the Publishing Working Group for their contributions to this specification:

The Working Group would also like to thank the members of the Digital Publishing Interest Group for all the hard work they did paving the road for this specification.