Open Annotation, Specifiers and Specific Resources tutorial

Cambridge Semantic Web MeetupMay 14th 2013 1Open Annotation Community Group

http://www.w3.org/community/openannotation/

Open Annotation Data Model:Specifiers and Specific Resources

Paolo Ciccarese [email protected] Harvard Medical School @paolociccarese

Robert Sanderson [email protected] Los Alamos National Laboratory @azaroth42

(Community Group Co-Chairs)

Massachusetts General Hospital



Specifiers and 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



Core Data Model

Annotation: The conceptual linkage between body and targetBody: The comment or resource which is “about” the TargetTarget: The resource which is being discussed



Specific Resources

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



Specific Resources



Specific Resources also for the Body



Specific Resources also for the Body



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



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 selectorsCommunities may also define their own










Selectors defined:• Fragment Selector

• Range Selectors:• Text Position Selector• Text Quote Selector• Data Position Selector

• Area Selectors• SVG Selector



Core Data Model: Fragment URIs



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









Specifiers: SVG Selector

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



Specifiers: SVG Selector

Note that the client downloads the SVG resource in this case



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



Specifiers: Text Quote Selector



Specifiers: Text Quote Selector



Specifiers: Text Position Selector



Specifiers: Text Position Selector



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)



Specifiers: Time State



Specifiers: Time State



Specifiers: HTTP Request State



Specifiers: HTTP Request State



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



Specifiers: CSS Style



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



Specifiers: Scope

Technology

Open Annotation, Specifiers and Specific Resources tutorial