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.
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:
the nature of the canonical identifier;
whether or not the address should specify a specific resource or only refer to a directory (i.e.,
rely on a default document being served);
differences in linking from the primary entry page to the manifest and from a publication resource
to the primary entry page; and
the processing of the manifest, in particular the inheritance of information from the primary entry
page (e.g., title or language information).
As well, reviews of the following areas were intended to be undertaken only when the specification
stabilized:
security, such as issues around cross-origin resource sharing and the exact origin for Web
Publication resources;
privacy, both as it relates to the maintenance of stored content and user-identifiable information;
and
user agent implementation of features.
Introduction
Scope
This specification defines three key concepts:
a general manifest format to describe publications;
a concrete format using the manifest to represent publications on the Web (Web
Publications); and
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:
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.
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.
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.
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.
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 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.
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.
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.
A digital publication'smanifest 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 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 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.
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.
Links
With the exception of the descriptive properties,
manifest properties typically link to one or more resources. When a property requires a
link value, the link MUST be expressed in one of the following two ways:
Manifest URLs are restricted to only the http and httpsschemes [[!url]]. URLs MUST
dereference to a resource, although user agents are not required to dereference all URLs in
the manifest.
In the case of a linked manifest, the base URL is URL of
the manifest resource.
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).
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.
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.”
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.
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.
The global duration indicates the overall length of a time-baseddigital 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]].
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.
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;
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]]:
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:
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]].
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.
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]].
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.
The reading progression establishes the reading
direction from one resource to the next within a digital publication. It is expressed
using the readingDirection property.
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.
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.
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
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.
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
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.
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).
The links property provides a list of resources that are not
required for the processing and rendering of a digital publication (i.e., the content
of the publication remains unaffected even if these resources are not available).
Term
Description
Required Value
Value Category
[[!schema.org]] Mapping
links
One or more of:
a string, representing the URL of the resource; or
Linked resources are typically made available to user agents to augment or enhance the
processing or rendering, such as:
a privacy policy or license that the user agent can offer a link to from a shelf;
a metadata record that the user agent can use to discover and display more information
about the publication;
a dictionary of terms the user agent can process to provide enhanced language help;
Links can also be used to identify resources used in the online rendering of a publication,
but that are not essential to include when the publication is taken offline or packaged
(e.g., to minimize the size). These include:
large font files that enhance the appearance of the publication but are not vital to its
display (i.e., a fallback font will suffice);
third-party scripts that are not intended for use when a publication is taken offline or
packaged (e.g., tracking scripts).
The links list SHOULD include resources necessary to render a linked resource
(e.g., scripts, images, style sheets).
User agents MAY ignore linked resources, and are not required to take them offline with a
publication. These resources SHOULD NOT be included when packaging a publication.
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:
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.
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.
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.
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.
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.
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).
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.
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:
through the use of relations defined in [[!iana-relations]]; or
When a manifest is embedded within an HTML document, the link MUST
include a fragment identifier that references the script element that contains the
manifest (see ).
The exact value of rel is still to be agreed upon
and should be registered by IANA.
The following details might be moved to the lifecycle section in a future
draft.
When a resource links to multiple manifests, a user agent MAY choose to present one or more
alternatives to the end user, or choose a single alternative on its own. The user agent MAY
choose to present any manifest based upon information that it possesses, even one that is not
explicitly listed as a parent (e.g., based upon information it calculates or acquires out of
band). In the absence of a preference by user agent implementers, selection of the first
manifest listed is suggested as a default.
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.
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.
Let json be the result of parsingtext. If parsing throws an error,
terminate this algorithm.
If Type(json) is not Object, terminate this algorithm.
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 .
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.
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
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"}.
let lang string represent the default language, set to:
the value of the lang value for the script element in
document (when set); or
() 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:
() 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.
() 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,
() 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,
() 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,
() 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,
() 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.
(, extension point) if a profile defines its own
canonicalization steps for profile specific terms, those steps are executed at this
point.
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).
Perform data cleanup operations on manifest, possibly removing data, as well
as raising warnings.
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.
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.
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.
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.
Check whether manifest["datePublished"] is a valid date or date-time,
per [[!iso8601]]. If the check fails, issue a warning.
Check whether manifest["dateModified"] is a valid date or date-time,
per [[!iso8601]]. If the check fails, issue a warning.
Check whether manifest["duration"] is a valid duration value,
per [[!iso8601]]. If the check fails, issue a warning.
Extension point: process any proprietary, profile specific, and/or other supported
members at this point in the algorithm.
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.
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.
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.
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.
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:
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.
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).
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.
The steps for
obtaining a manifest, starting from the primary entry page, are given by the
following algorithm.
If the primary entry page does not have the media type text/html or
application/xhtml+xml, terminate this algorithm.
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.
If origin is an [[!html]] opaque origin, terminate this algorithm.
If manifest link is null, terminate this algorithm.
If manifest link's href attribute's value is the empty string,
terminate this algorithm.
If the href attribute value of manifest link is equivalent to [[!URL]]
origin:
If it has a non-null fragment
identifying an identifier id in Document:
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.
If embedded manifest script is null, terminate this
algorithm.
Let base be the value of baseURI of the script element.
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.
Otherwise:
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.
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.
If the manifest link's crossOrigin attribute's value is
'use-credentials', then set request's credentials to
'include'.
Await the result of performing a fetch with request, letting
response be the result.
If response is a network error, terminate this algorithm.
Let text be the result of UTF-8 decoding response's body.
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.
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:
Identify the table of contents resource:
If a resource in either the default reading
order or resource-list is identified with a
rel value including
contents [[!iana-link-relations]], the corresponding
url value identifies the table of contents resource. If there are
several such resources, the first one MUST be used, with the default reading order taking precedence over
resource-list.
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.
User agents MUST compute the page list as follows:
Identify the page list resource:
If a resource in either the default reading
order or resource-list is identified with a
rel value including pagelist, the corresponding
url value identifies the page list resource. If there are several
such resources, the first one MUST be used, with the default reading order taking precedence over
resource-list.
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.
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:
It MUST adhere to the manifest format requirements defined in .
The generic canonicalization steps described in MUST remain
valid for the extended manifest. To achieve this, and if new terms are added to the general , then:
The term SHOULD be categorized, if applicable, to one or more of the general term
categories used in the algorithm (e.g., array or localizable string). This means the relevant
canonicalization steps will be automatically executed for those terms
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.
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]].
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.
List of Links
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.
Let toc be a object that represents the table of contents and initialize it as
follows:
Create a name property for toc that represents the title of the
table of contents and set to an empty string.
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.
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.
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.
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.
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.
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 tocname 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).
If the name property of toc is an empty string, set
name to null.
If current toc branch is not null:
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.
Otherwise, push the object in current toc branch onto the stack
and set current toc branch to null.
Otherwise, if the stack is empty:
If the entries property of toc is
null or a non-empty array, exit the element and
continue processing with the next element.
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.
Create name, url, type, and
rel properties for the object and set them to empty
strings.
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.
If entries property of current toc branch contains an
empty array, set its value to null.
If the stack contains one or more entries:
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;
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.
Otherwise, add the object in current toc branch to the
entries array of toc.
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.
When entering an anchor element and current toc branch is not
null:
Run these steps:
If the name property of current toc branch is not an
empty string, do nothing.
Otherwise:
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.
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.
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.
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.
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.
Otherwise: do nothing.
Explanation
For all other elements, this steps allows their descendant elements to continue
to be processed.
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 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.
Audiobook
A manifest for an audiobook. The canonical
version of this manifest is also available.
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. 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. 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). 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. 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. 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.
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:
Greg Albers (J. Paul Getty Trust)
Franco Alvarado (Macmillan Learning)
Boris Anthony (The Rebus Foundation)
Luc Audrain (Hachette Livre)
Baldur Bjarnason (The Rebus Foundation)
Laura Brady (W3C Invited Expert)
Steve Breault (Scenarex Inc.)
Don Brutzman (Web3D Consortium)
Kaylin Bugbee (Earth Science Data Systems Program)
Yu-Wei Chang (Taiwan Digital Publishing Forum)
Fred Chasen (W3C Invited Expert)
Timothy Cole (University of Illinois at Urbana-Champaign)
Simon Collinson (Rakuten, Inc.)
Rachel Comerford (Macmillan Learning)
Garth Conboy (Google, Inc., chair)
Juan Corona (Evident Point Software)
Christopher Cosner (Stanford University)
Dave Cramer (Hachette Livre)
Greg Davis (Pearson plc)
Romain Deltour (DAISY Consortium)
Marisa DeMeglio (DAISY Consortium)
Vagner Diniz (NIC.br - Brazilian Network Information Center)
Kenneth Dougherty (Pearson plc)
Brady Duga (Google, Inc.)
Ben Dugas (Rakuten, Inc.)
Roger Espinosa (University of Michigan)
Reinaldo Ferraz (NIC.br - Brazilian Network Information Center)
Heather Flanagan (RFC Editor)
Teenya Franklin (Pearson plc)
Jun Gamo (Voyager Japan, Inc.)
Michael Goodman (Wiley)
Markku Hakkinen (Educational Testing Service)
Katie Haritos-Shea (Knowbility)
Geoff Jukes (Blackstone Audio, Inc.)
Deborah Kaplan (W3C Invited Expert)
Bill Kasdorf (Book Industry Study Group)
George Kerscher (DAISY Consortium)
Yuri Khramov (Evident Point Software)
Masakazu Kitahara (Voyager Japan, Inc.)
Toshiaki Koike (Voyager Japan, Inc.)
Charles LaPierre (Benetech)
Mustapha Lazrek (Microsoft Corp.)
Laurent Le Meur (EDRLab)
Vladimir Levantovsky (Monotype)
Mia Lipner (Pearson plc)
Phil Madans (Hachette Livre)
Christopher Maden (University of Illinois at Urbana-Champaign)
Dmitry Markushevich (Evident Point Software)
keith mcfarland (Blackstone Audio, Inc.)
Jonathan McGlone (University of Michigan)
Hugh McGuire (The Rebus Foundation)
Nellie McKesson (W3C Invited Expert)
Selma Morais (NIC.br - Brazilian Network Information Center)
Jasmine Mulliken (Stanford University)
Cristina Mussinelli (Fondazione LIA)
Christos Nikolakakos (Wiley)
Gregorio Pellegrino (Fondazione LIA)
Fernando Pinto da Silva (EDRLab)
Nicholas Polys (Web3D Consortium)
Chris Powell (University of Michigan)
Jeff Printy (Macmillan Learning)
Ryan Pugatch (Hachette Livre)
Joshua Pyle (Wiley)
Wendy Reid (Rakuten, Inc., chair)
Florian Rivoal (W3C Invited Expert)
Leonard Rosenthol (Adobe)
Robert Sanderson (J. Paul Getty Trust)
Jodi Schneider (University of Illinois at Urbana-Champaign)
Ben Schroeter (Pearson plc)
Tzviya Siegman (Wiley, chair)
Avneesh Singh (DAISY Consortium)
Adam Sisco (Earth Science Data Systems Program)
David Stroup (Pearson plc)
Mateus Teixeira (W. W. Norton & Company)
Jonathan Thurston (Pearson plc)
Yukio Tomikura (Kodansha, Publishers, Ltd.)
Ben Walters (Microsoft Corp.)
Daniel Weck (EDRLab, DAISY Consortium)
John Weise (University of Michigan)
Jason White (Educational Testing Service)
Richard Wright (EDRLab)
Jeff Xu (Rakuten, Inc.)
Evan Yamanishi (W. W. Norton & Company)
Maurice York (University of Michigan)
Junichi Yoshii (Kodansha, Publishers, Ltd.)
Benjamin Young (Wiley)
Mohamed ZERGAOUI (INNOVIMAX)
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.