3.2.1 External Web Resources

Web Resources are identified with a IRI and have various properties, often including a format or language for the resource's content. This information may be recorded as part of the Annotation, even if the representation of the resource must be retrieved from the Web.

Example Use Case: Beatrice records a long analysis of a patent, and publishes the audio on her website as an mp3. She then creates an Annotation with the mp3 as the body, and the PDF of the patent as the target.

Model

Example

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno2",
  "type": "Annotation",
  "body": {
    "id": "http://example.org/analysis1.mp3",
    "format": "audio/mpeg",
    "language": "fr"
  },
  "target": {
    "id": "http://example.gov/patent1.pdf",
    "format": "application/pdf",
    "language": ["en", "ar"],
    "textDirection": "ltr",
    "processingLanguage": "en"
  }
}

3.2.2 Classes

It is useful for clients to know the general type of a Web Resource in advance. If the client cannot render videos, then knowing that the Body is a video will allow it to avoid needlessly downloading a potentially large content stream. For resources that do not have obvious media types, such as many data formats, it is also useful for a client to know that a resource with the format text/csv should not simply be rendered as plain text, despite the first part of the media type, whereas application/pdf may be able to be rendered by the user agent despite the main type being 'application'.

Example Use Case: Corina shoots a video of her comment about a website on her phone and uploads it. She associates the video with the website via an Annotation, and her client adds types as a hint to consuming systems.

Model

Example

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno3",
  "type": "Annotation",
  "body": {
    "id": "http://example.org/video1",
    "type": "Video"
  },
  "target": {
    "id": "http://example.org/website1",
    "type": "Text"
  }
}

3.2.3 Segments of External Resources

Many Annotations involve part of an External Web Resource, rather than its entirety. In the Web [webarch], segments of resources are identified using IRIs with a fragment component that at the same time both describes how to extract the segment of interest from the resource, and identifies the extracted content. For simple Annotations, it is valuable to be able to use these IRIs with a fragment component as the identifier for either Body or Target.

Example Use Case: Dawn wants to describe a particular region of an image. She highlights that area in her client and types in the description. Her client then constructs an IRI with an appropriate fragment component as the target.

Model

It is important to be aware of the consequences of using an IRI with a fragment component, and the restrictions that using them places on implementations.

• Fragments are defined with respect to individual media types. For example, HTML has a specific set of semantics regarding the meaning of the fragment part of the IRI.
• Not every media type has a fragment specification. For example, Office documents might have a media-type and be published on the web, but not have semantics associated with the fragment part of the IRI.
• Even if a media type does have a fragment definition, it is often not possible to describe the segment of interest sufficiently precisely. For example, fragments for HTML cannot be used to describe an arbitrary range of text.
• It is not possible to determine with certainty what is being identified without knowing the media type, as the same fragment string might be possible in different specifications. For example, the same fragment string could identify either a rectangular area in an image, or a strangely named section of an HTML document.
• IRIs with a fragment component are not compatible with other methods of describing the segment more specifically. For example, it is not possible to describe how to retrieve the correct representation, add style information, or associate a role with the resource, using such IRIs. The method to accomplish these requirements is described in the Fragment Selector portion of the Specific Resources section.
• As IRIs are considered to be opaque strings, annotation systems may not discover annotations with fragment components when searching by means of the IRI without the fragment. For example, an Annotation with the Target http://example.com/image.jpg#xywh=1,1,1,1 would not be discovered in a simple search for http://example.com/image.jpg, even though it is part of it.

Example

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno4",
  "type": "Annotation",
  "body": "http://example.org/description1",
  "target": {
    "id": "http://example.com/image1#xywh=100,100,300,300",
    "type": "Image",
    "format": "image/jpeg"
  }
}

3.2.4 Embedded Textual Body

In many situations, the Body of the Annotation will be in a text format, and created at the same time as the Annotation without a separate IRI. In these cases, the Body's text can be included as part of the Annotation to avoid having to interact with multiple systems. The Body may also have the features of External Web Resources, including especially the language of the text and the format that it is conveyed in.

Example Use Case: Emily writes a comment about how much she likes an image on a photo sharing website. Her client creates an Annotation with the comment embedded within it, and adds that it is in French and formatted using HTML.

Model

Systems SHOULD assume that Textual Bodies have the Text class, described in Classes above, even if it is not explicitly included in the type property.

The properties of External Web Resources, such as language and format also apply to embedded Textual Body resources.

Example

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno5",
  "type": "Annotation",
  "body": {
    "type" : "TextualBody",
    "value" : "<p>j'adore !</p>",
    "format" : "text/html",
    "language" : "fr"
  },
  "target": "http://example.org/photo1"
}

3.2.5 String Body

The simplest type of Body is a plain text string, without additional information or properties. This type of Body is useful for the simplest of Annotations only, and is NOT RECOMMENDED for uses where the Body may need to be referred to from outside of the Annotation.

Example Use Case Franceska wants to create a quick Annotation from a simple, command line client. She creates the JSON serialization in a text file and sends it to her Annotation server to maintain.

Model

There are several restrictions on when this form may be used and how it is to be interpreted.
The string Body:

• MUST be a single xsd:string and the data type MUST NOT be expressed in the serialization.
• MUST NOT have a language associated with it.
• MUST be interpreted as if it were the value of the value property of a Textual Body.
• MUST be interpreted as if the Textual Body resource had a format property with the value text/plain.
• MUST NOT have the value of other properties of the Textual Body inferred from similar properties on the Annotation resource.

If any of the interpretations above are not correct, then the TextualBody construction MUST be used instead.

Example

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno6",
  "type": "Annotation",
  "bodyValue": "Comment text",
  "target": "http://example.org/target1"
}

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno7",
  "type": "Annotation",
  "body": {
    "type": "TextualBody",
    "value": "Comment text",
    "format": "text/plain"
  },
  "target": "http://example.org/target1"
}

3.2.6 Cardinality of Bodies and Targets

Some Annotations may not have a Body at all, such as a simple highlight or bookmark without any accompanying text. It is also possible for an Annotation to have multiple Bodies and/or Targets. In this case, each Body is considered to be equally related to each Target individually, rather than to the set of all of the Targets.

Example Use Case: Gretchen highlights a particular region of her ebook in green and, knowing what such a highlight means, she does not give a comment. Her client associates a stylesheet with the Annotation, and does not create a body at all.

Example Use Case: Hannah associates a tag and a description with two images using a single annotation.

Model

The body relationship is omitted when there is no Body for the Annotation.

The body and/or target relationships of the Annotation may be arrays rather than a single object. The values may be either strings containing the IRI of the resource or objects.

Example

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno8",
  "type": "Annotation",
  "target": "http://example.org/ebook1"
}

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno9",
  "type": "Annotation",
  "body": [
    "http://example.org/description1",
    {
      "type": "TextualBody",
      "value": "tag1"
    }
  ],
  "target": [
    "http://example.org/image1",
    "http://example.org/image2"
  ]
}

3.2.7 Choice Between Bodies

A Choice has an ordered list of resources from which an application should select only one to process or display. The order is given from the most preferable to least preferable, according to the Annotation's creator or publisher.

Example Use Case: Irina writes up her discussion of a particular website in both French and English. As the two posts are equivalent, there is no need to display both, and instead she wants French speakers to see the French comment, and everyone else to see the English version. Her client creates as Choice with the English comment listed first.

Model

Example

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno10",
  "type": "Annotation",
  "body": {
    "type": "Choice",
    "items": [
      {
        "id": "http://example.org/note1",
        "language": "en"
      },
      {
        "id": "http://example.org/note2",
        "language": "fr"
      }
    ]
  },
  "target": "http://example.org/website1"
}

3.3.1 Lifecycle Information

The person, organization or machine responsible for the Annotation or referenced resource deserves credit for their contribution, and the time at which those resources are created is useful for display ordering and filtering out old, potentially irrelevant content. The creator of the Annotation is also useful for determining the trustworthiness of the Annotation. The software used to create and serialize the Annotation, along with when that activity occurred, is useful for both advertising and debugging issues.

Example Use Case: Jane writes a review of a restaurant online, and wishes to be associated with that review so that her friends know that it was her review and can trust it. Her client adds her account's identity, and its own identity, to the Annotation and the appropriate timestamps for when the resources were created.

Model

Example

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno11",
  "type": "Annotation",
  "creator": "http://example.org/user1",
  "created": "2015-01-28T12:00:00Z",
  "modified": "2015-01-29T09:00:00Z",
  "generator": "http://example.org/client1",
  "generated": "2015-02-04T12:00:00Z",
  "body": {
    "id": "http://example.net/review1",
    "creator": "http://example.net/user2",
    "created": "2014-06-02T17:00:00Z"
  },
  "target": "http://example.com/restaurant1"
}

3.3.2 Agents

More information about the agents involved in the creation of an Annotation is normally required beyond an IRI that identifies them. This includes whether they are an individual, a group or a piece of software and properties such as real name, account nickname, and email address.

Example Use Case: Kelly wants to submit an Annotation to a system that does not manage her identity, and would like a pseudonym to be displayed. Her client adds this information to the Annotation to send to the service.

Model

Example

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno12",
  "type": "Annotation",
  "creator": {
    "id": "http://example.org/user1",
    "type": "Person",
    "name": "My Pseudonym",
    "nickname": "pseudo",
    "email_sha1": "58bad08927902ff9307b621c54716dcc5083e339"
  },
  "generator": {
    "id": "http://example.org/client1",
    "type": "Software",
    "name": "Code v2.1",
    "homepage": "http://example.org/client1/homepage1"
  },
  "body": "http://example.net/review1",
  "target": "http://example.com/restaurant1"
}

3.3.3 Intended Audience

Beyond the agents that are associated with the creation and management of the Annotation and other resources, it is also useful to know the audience or class of consuming agent that the resource is intended for. This allows for the roles (such as teacher versus student) or properties of the class (such as a suggested age range) of the intended audience to be recorded.

Example Use Case: Lynda writes some notes about using a particular textbook to teach a class. She adds that the intended audience of the Annotation is teachers (who are using the textbook), to distinguish from other Annotations that might have an audience of the students (who are also using the textbook, but to learn from).

Model

Further properties that describe the audience are used from schema.org's Audience classes. The properties and class names MUST be prefixed in the JSON with schema: to ensure that they are uniquely distinguished from any other properties or classes.

The use of audience does not imply nor enable any access restriction to prevent the annotation from being seen. Systems SHOULD use the information for filtering the display of Annotations based on their knowledge of the user, and not assume that the Annotation or other resources will require authentication and authorization.

Example

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno13",
  "type": "Annotation",
  "audience": {
    "id": "http://example.edu/roles/teacher",
    "type": "schema:EducationalAudience",
    "schema:educationalRole": "teacher"
  },
  "body": "http://example.net/classnotes1",
  "target": "http://example.com/textbook1"
}

3.3.4 Accessibility of Content

Access to information is recognized as a basic human right by the United Nations. The Web is able to remove barriers to communication and interaction regardless of various physical impediments. This supports social inclusion, but also increases the potential audience of the information. For resources that are used as the Body or Target of an Annotation, it is valuable to record the features of that resource that provide easier access for users with various and diverse ranges of ability.

Example Use Case: Megan has very limited ability to hear sound, and prefers to read captions when interacting with videos. She uses her annotation client to make a comment on such a video, and to help others in the same situation, the client includes that the video has this accessibility feature.

Model

Example

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno14",
  "type": "Annotation",
  "motivation": "commenting",
  "body": "http://example.net/comment1",
  "target": {
    "id": "http://example.com/video1",
    "type": "Video",
    "accessibility": "captions"
  }
}

3.3.5 Motivation and Purpose

In many cases it is important to understand the reasons why the Annotation was created, or why the Textual Body was included in the Annotation, not just the times and agents involved. These reasons are provided by declaring the motivation for the Annotation's creation or the purpose for the inclusion of the Textual Body in the Annotation; the "why" rather than the "who" and "when" described in the previous sections.

Example Use Case: Noelle annotates a resource intending to bookmark it for future reference, and provides a description and a tag to make it easier to find again. Her client adds the right motivations to the Annotation and the Textual Body resources to capture this.

Model

Example

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno15",
  "type": "Annotation",
  "motivation": "bookmarking",
  "body": [
    {
      "type": "TextualBody",
      "value": "readme",
      "purpose": "tagging"
    },
    {
      "type": "TextualBody",
      "value": "A good description of the topic that bears further investigation",
      "purpose": "describing"
    }
  ],
  "target": "http://example.com/page1"
}

3.3.6 Rights Information

It is common practice to associate a license or rights statement with a resource, in order to describe the conditions under which it may be used. This allows the user to make appropriate use of the resource, as well as allowing some automated systems to confirm that the usage is permitted. As the Annotation, Bodies, and Targets might be created with different licences or rights, each can be described separately. The rights of resources other than the Annotation itself are considered informative hints to a consuming client application.

Example Use Case: Ophelia writes a review of a product and wishes to be known as the author of the review, however does not mind how the Annotation that relates the review and the product together is used. She asserts these two separate rights statements with the Annotation and Body individually. She does not know the rights asserted on the target resource, so does not specify any.

Model

Example

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno16",
  "type": "Annotation",
  "rights": "https://creativecommons.org/publicdomain/zero/1.0/",
  "body": {
    "id": "http://example.net/review1",
    "rights": "http://creativecommons.org/licenses/by-nc/4.0/"
  },
  "target": "http://example.com/product1"
}

3.3.7 Other Identities

In a massively distributed system such as the Web, information is often copied. In order to track the provenance of the Annotation and other related resources, it is possible to record additional IRIs that also identify the resource. These may be dereferencable "permalinks", identities assigned by a client offline without any knowledge of the web, or simply the location where the current harvesting system discovered the resource.

Example Use Case: Petra creates an Annotation and sends it to multiple systems to maintain, one personal and one public. She wants to ensure that the copies can be aligned, and so she sets a UUID as the canonical IRI, allowing the service to assign an HTTP IRI for it. A subsequent system then harvests the public copy, maintaining the canonical UUID as discovered, then moves the original HTTP IRI to via, replacing it with an IRI under its control.

Model

Example

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno17",
  "type": "Annotation",
  "canonical": "urn:uuid:dbfb1861-0ecf-41ad-be94-a584e5c4f1df",
  "via": "http://other.example.org/anno1",
  "body": {
    "id": "http://example.net/review1",
    "rights": "http://creativecommons.org/licenses/by/4.0/"
  },
  "target": "http://example.com/product1"
}

4.2.1 Fragment Selector

As the most well understood mechanism for selecting a Segment is to use the fragment part of an IRI defined by the representation's media type, it is useful to allow this as a description mechanism via a Selector. This allows existing and future fragment specifications to be used with Specific Resources in a consistent way. To be clear about which fragment type is being used, the Selector may refer to the specification that defines it.

Example Use Case: Sally wants to associate part of a video as the description of an image. She selects the time range within the video and clicks that it is describing the target. Her client then creates the Annotation using a SpecificResource with a FragmentSelector and the describing Motivation.

Model

It is RECOMMENDED to use FragmentSelector as a consistent method compatible with other means of describing SpecificResources, rather than using the IRI with a fragment directly. Consuming applications SHOULD be aware of both.

The following IRIs are some of the specifications that define the semantics of fragments, and hence may be used with the conformsTo relationship. Other IRIs MAY also be used.

Example

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno20",
  "type": "Annotation",
  "body": {
    "source": "http://example.org/video1",
    "purpose": "describing",
    "selector": {
      "type": "FragmentSelector",
      "conformsTo": "http://www.w3.org/TR/media-frags/",
      "value": "t=30,60"
    }
  },
  "target": "http://example.org/image1"
}

4.2.2 CSS Selector

One of the most common ways to select elements in the HTML Document Object Model is to use CSS Selectors [CSS3-selectors]. CSS Selectors allow for a wide variety of well supported ways to describe the path to an element in a web page, and thus cover many of the basic use cases for Web Annotation. Results are not defined for when a CSS Selector is applied to a representation that does not conform to the Document Object Model.

Note that CSS may also be used for styling a resource within an annotation. This class is specifically to re-use the CSS Selector mechanism to select a segment of a resource that conforms to the Document Object Model.

Example Use Case: Teynika selects a paragraph in a web page that she wishes to write a note about. Her client calculates a CSS path that cleanly identifies that element and adds it to the annotation.

Model

Example

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno21",
  "type": "Annotation",
  "body": "http://example.org/note1",
  "target": {
    "source": "http://example.org/page1.html",
    "selector": {
      "type": "CssSelector",
      "value": "#elemid > .elemclass + p"
    }
  }
}

4.2.3 XPath Selector

Another common method of selecting elements and content within a resource that supports the Document Object Model (DOM), such as documents in XML or HTML, is to use an XPath selection [DOM-Level-3-XPath]. XPath allows a great deal of flexibility when describing the path through the structure to the selected content. Results are not defined for when an XPath Selector is applied to a representation that does not conform to the DOM.

Example Use Case: Ulrika selects a span within a table in an HTML page and writes a note about the content. To refer explicitly to this element, her client carefully constructs an XPath to identify it as the target of the Annotation.

Model

Example

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno22",
  "type": "Annotation",
  "body": "http://example.org/note1",
  "target": {
    "source": "http://example.org/page1.html",
    "selector": {
      "type": "XPathSelector",
      "value": "/html/body/p[2]/table/tr[2]/td[3]/span"
    }
  }
}

4.2.4 Text Quote Selector

This Selector describes a range of text by copying it, and including some of the text immediately before (a prefix) and after (a suffix) it to distinguish between multiple copies of the same sequence of characters.

For example, if the document were again "abcdefghijklmnopqrstuvwxyz", one could select "efg" by a prefix of "abcd", the match of "efg" and a suffix of "hijk".

Example Use Case: Valeria selects a typo ('anotation') in a web page and adds a comment that it should be replaced with the correct spelling ('annotation').

Model

The selection of the text MUST be in terms of unicode code points (the "character number"), not in terms of code units (that number expressed using a selected data type). Selections SHOULD NOT start or end in the middle of a grapheme cluster. The selection MUST be based on the logical order of the text, rather than the visual order, especially for bidirectional text. For more information about the character model of text used on the web, see [charmod].

The text MUST be normalized before recording in the Annotation. Thus HTML/XML tags SHOULD be removed, and character entities SHOULD be replaced with the character that they encode. Note that this does not affect the state of the content of the document being annotated, only the way that the content is recorded in the Annotation document.

If, after processing the prefix, exact, and suffix, the user agent discovers multiple matching text sequences, then the selection SHOULD be treated as matching all of the matches.

Example

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno23",
  "type": "Annotation",
  "body": "http://example.org/comment1",
  "target": {
    "source": "http://example.org/page1",
    "selector": {
      "type": "TextQuoteSelector",
      "exact": "anotation",
      "prefix": "this is an ",
      "suffix": " that has some"
    }
  }
}

4.2.5 Text Position Selector

This Selector describes a range of text by recording the start and end positions of the selection in the stream. Position 0 would be immediately before the first character, position 1 would be immediately before the second character, and so on. The start character is thus included in the list, but the end character is not.

For example, if the document was "abcdefghijklmnopqrstuvwxyz", the start was 4, and the end was 7, then the selection would be "efg".

Example Use Case: Wendy writes a review of an ebook that does not allow its content to be extracted and copied. Her client describes the selection using its start and end position in the content.

Model

The text MUST be selected and normalized in the same way as for the Text Quote Selector before counting the number of characters to determine the start and end positions.

Example

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno24",
  "type": "Annotation",
  "body": "http://example.org/review1",
  "target": {
    "source": "http://example.org/ebook1",
    "selector": {
      "type": "TextPositionSelector",
      "start": 412,
      "end": 795
    }
  }
}

4.2.6 Data Position Selector

Similar to the Text Position Selector, the Data Position Selector uses the same properties but works at the byte in bitstream level rather than the character in text level.

Example Use Case: Xena writes comments about regions of online disk images for forensic purposes and describing emulation requirements. Her client generates the start and end positions from the binary stream, rather than the more human readable display she is using.

Model

Example

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno25",
  "type": "Annotation",
  "body": "http://example.org/note1",
  "target": {
    "source": "http://example.org/diskimg1",
    "selector": {
      "type": "DataPositionSelector",
      "start": 4096,
      "end": 4104
    }
  }
}

4.2.7 SVG Selector

An SvgSelector defines an area through the use of the Scalable Vector Graphics [SVG11] standard. This allows the user to select a non-rectangular area of the content, such as a circle or polygon by describing the region using SVG. The SVG may be either embedded within the Annotation or referenced as an External Web Resource.

Note that the SvgSelector uses SVG to select an area of a resource. Segments of an SVG representation may also be selected using selectors, including the FragmentSelector or even an SvgSelector.

Example Use Case: Yadira is tagging an old map online with a diagonal region for a historical road. Her client creates SVG polygon to describe the region, relative to the image content.

Model

The dimensions of the SVG shape or canvas MUST be relative to the dimensions of the Source resource, such that scaling the shape's size to the full size of the image correctly describes the desired area.

Example

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno26",
  "type": "Annotation",
  "body": "http://example.org/road1",
  "target": {
    "source": "http://example.org/map1",
    "selector": {
      "id": "http://example.org/svg1",
      "type": "SvgSelector"
    }
  }
}

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno27",
  "type": "Annotation",
  "body": "http://example.org/road1",
  "target": {
    "source": "http://example.org/map1",
    "selector": {
      "type": "SvgSelector",
      "value": "<svg:svg> ... </svg:svg>"
    }
  }
}

4.2.8 Range Selector

Selections made by users may be extensive and/or cross over internal boundaries in the representation, making it difficult to construct a single selector that robustly describes the correct content. A Range Selector can be used to identify the beginning and the end of the selection by using other Selectors. In this way, two points can be accurately identified using the most appropriate selection mechanisms, and then linked together to form the selection. The selection consists of everything from the beginning of the starting selector through to the beginning of the ending selector, but not including it.

Example Use Case: Zara wants to comment on two adjacent cells in a table that is part of a web page. She selects the two cells and her client constructs XPaths to the the first cell, and the cell that immediately follows the second. Her client then creates a Range Selector with the first XPath Selector as the start, and the second XPath selector as the end.

Model

Example

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno28",
  "type": "Annotation",
  "body": "http://example.org/comment1",
  "target": {
    "source": "http://example.org/page1.html",
    "selector": {
      "type": "RangeSelector",
      "startSelector": {
        "type": "XPathSelector",
        "value": "//table[1]/tr[1]/td[2]"
      },
      "endSelector": {
        "type": "XPathSelector",
        "value": "//table[1]/tr[1]/td[4]"
      }
    }
  }
}

4.2.9 Refinement of Selection

It may be easier, more reliable or more accurate to specify the segment of interest of a resource as a selection of a selection, rather than as a selection of the complete resource. Particularly for resources that contain other resources, such as various packaging formats, this also allows decomposition of the selection mechanisms when the components do not have unique identifiers. This is accomplished by having selectors chained together, where each refines the results of the previous one.

Example Use Case: Alexandra selects a paragraph of text and then a short phrase within it to comment on. Her client records the phrase as a TextQuoteSelector that further modifies a FragmentSelector used to identify the paragraph that the phrase is part of.

Model

Example

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno29",
  "type": "Annotation",
  "body": "http://example.org/comment1",
  "target": {
    "source": "http://example.org/page1",
    "selector": {
      "type": "FragmentSelector",
      "value": "para5",
      "refinedBy": {
        "type": "TextQuoteSelector",
        "exact": "Selected Text",
        "prefix": "text before the ",
        "suffix": " and text after it"
      }
    }
  }
}

4.3.1 Time State

A Time State resource records the time at which the resource is appropriate for the Annotation, typically the time that the Annotation was created and/or a link to a persistent copy of the current version. The timestamp for the resource could be resolved via the Memento protocol, described in RFC 7089 [rfc7089].

Example Use Case: Carla makes a note about the current state of the front page of a news website, and flags that the page is likely to change often. Her client adds in a State with the current time to describe the version of the page being annotated.

Model

Example

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno31",
  "type": "Annotation",
  "body": "http://example.org/note1",
  "target": {
    "source": "http://example.org/page1",
    "state": {
      "type": "TimeState",
      "cached": "http://archive.example.org/copy1",
      "sourceDate": "2015-07-20T13:30:00Z"
    }
  }
}

4.3.2 Request Header State

As there are potentially many representations that can be delivered from a resource with a single IRI, and a Specific Resource may only apply to one of them, it is important to be able to record the HTTP Request headers that need to be sent to retrieve the correct representation. The HttpRequestState resource maintains a copy of the headers to be replayed when obtaining the representation.

Example Use Case: Devina retrieves a PDF representation of a web resource that can deliver HTML, PDF or plain text and then writes a description about it. She signals that her description is only about the PDF representation. Her client then includes a State to describe how to retrieve the target representation.

Model

Example

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno32",
  "type": "Annotation",
  "body": "http://example.org/description1",
  "target": {
    "source": "http://example.org/resource1",
    "state": {
      "type": "HttpRequestState",
      "value": "Accept: application/pdf"
    }
  }
}

4.3.3 Refinement of State

Similar to the refinement of selection, it may be easier, more reliable or more accurate to specify the appropriate state of the resource as a hierarchy of atomic State resources. This is particularly appropriate for representing the combination of a State that reflects an internal transformation along with the results of a State that describes an external request. This decomposition is accomplished by having the states chained together in the same way as Selectors.

Further, given that the State(s) will likely result in a specific representation, there may be specific Selectors that are appropriate for describing the segment of the representation. In order to accommodate this, States may also be refined by Selectors.

Example Use Case: Erin writes a comment about a travel e-book which has many versions available over time, and is available in different formats. She is particularly commenting on a specific version and format, so her client adds both a TimeState to capture the time and an HttpRequestState to capture the format, and then a particular FragmentSelector that is appropriate to that format.

Model

Example

{
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "id": "http://example.org/anno33",
  "type": "Annotation",
  "body": "http://example.org/comment1",
  "target": {
    "source": "http://example.org/ebook1",
    "state": {
      "type": "TimeState",
      "sourceDate": "2016-02-01T12:05:23Z",
      "refinedBy": {
        "type": "HttpRequestState",
        "value": "Accept: application/pdf",
        "refinedBy": {
          "type": "FragmentSelector",
          "value": "page=10",
          "conformsTo": "http://tools.ietf.org/rfc/rfc3778"
        }
      }
    }
  }
}