Open Annotation, Specifiers and Specific Resources tutorial

Cambridge Semantic Web Meetup
May 14th 2013
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Open Annotation Community Group
http://www.w3.org/community/openannotation/
Open Annotation Data Model:
Specifiers and Specific Resources
Paolo Ciccarese
paolo.ciccarese@gmail.com
Harvard Medical School
@paolociccarese
Robert Sanderson
azaroth42@gmail.com
Los Alamos National Laboratory
@azaroth42
(Community Group Co-Chairs)
Massachusetts General Hospital

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Specifiersand Specific Resources
This module addresses several issues:
• Advanced Segmentation
• Fragments are not expressive enough for use cases
• Some media types do not have fragment definition at all
• Time and the Dynamic Web
• Representations change and keep the same URI
• Annotation may only apply to specific negotiated format
• Styling Annotation
• Style is vehicle for human-only semantics (eg red strike-through)
• Style may be referenced in comments (the green highlight)
• Scoping
• Eg. the web page being viewed while an image was annotated

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Core Data Model
Annotation: The conceptual linkage between body and target
Body: The comment or resource which is “about” the Target
Target: The resource which is being discussed

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Specific Resources
Specific Resource: A resource that is somehow more specific or more
precisely defined than the “source” resource
Source: The resource as identified by its URI

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Specific Resources

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Specific Resources also for the Body

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Specific Resources also for the Body

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Specifiers
There are four types of Specifier that describe how the Specific Resource
is different to the Source resource:
• Selector
• Describes a segment of the resource
• State
• Describes a state that the resource was in, via time or HTTP
• Style
• Describes a Style (using CSS) for the Annotation
• Scope
• References a resource which was being used for the Annotation

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Specifiers: Selectors
Selectors describe the segment of interest of a resource
Selectors are needed for several reasons:
• Many media types do not have fragment specifications
• Those that do often are not sufficiently precise in terms of description
• Without knowing the media type, it is not possible to know how to
interpret a fragment
• URIs are opaque strings, and systems normally do not try to look
within them for searching
• Combinations of segment plus State, Style or Scope
The specification defines some general, cross-community selectors
Communities may also define their own

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Selectors defined:
• Fragment Selector
• Range Selectors:
• Text Position Selector
• Text Quote Selector
• Data Position Selector
• Area Selectors
• SVG Selector

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Core Data Model: Fragment URIs

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Specifiers: Fragment Selector
Fragment Selector uses the fragment specifications to describe the
segment:
• Useful in combination with other Specifiers
• No need to reinvent the wheel!
• Allows Specific Resource URI to be reused
• Allows additional information to be attached, such as the specification
used to define the fragment
Current Fragment specifications include:
• HTML, XML, RDF/XML
• PDF
• Plain Text
• SVG
• Media Fragments

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Specifiers: SVG Selector
Media Fragments can only describe rectangles.
SVG Selector allows arbitrary paths, circles, and so forth.

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Specifiers: SVG Selector
Note that the client downloads the SVG resource in this case

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Specifiers: Text Selectors
Several intersecting issues require text based selectors:
• HTML, PDF and Plain Text have fragment specifications, but only
Plain Text allows arbitrary spans of text
• Other formats don’t have a specification at all
• One text selector could be reused across formats of the same text
• Quotations in Annotations allow otherwise protected texts to be
reproduced
• Without the quotation and instead using character
position, changes to the text will invalidate the selector
We introduce two selectors:
• Text Quote Selector
• Text Position Selector

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Specifiers: Text Quote Selector

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Specifiers: Text Quote Selector

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Specifiers: Text Position Selector

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Specifiers: Text Position Selector

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Specifiers: States
Selectors describe segments, but the URI of the Source identifies the
generic web resource, not a particular representation.
The web is dynamic, representations change based on many factors;
States allow us to record some of the factors to get back to the right
representation.
We introduce two States:
• TimeState:
• Time as a universal versioning mechanism,
and pointing to archived copies of the resource
• HttpRequestState
• Capture HTTP headers for content negotiation (etc)

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Specifiers: Time State

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Specifiers: Time State

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Specifiers: HTTP Request State

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Specifiers: HTTP Request State

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Specifiers: CSS Style
Some Annotations should maintain the style choices of the creator,
for example to not draw a black rectangle on an image of the night sky

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Specifiers: CSS Style

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Specifiers: Scope
It is often useful to know in which context a resource was annotated.
This is recorded as a Scope of the Specific Resource

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Specifiers: Scope

Open Annotation, Specifiers and Specific Resources tutorial

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