Preserving Semantics in the Web

Ralph R. SwickMIT LCS & W3Cswick@lcs.mit.edu

Semantic Web Goal

• Encourage humans and machines to put more specificity of meaning into the Web

to enable …• people to find definitions, constraints, translations

• machines to automate [portions of] processing

• preservation of intention across time & space

Annotea - Shared Annotations

• Human-level Annotation object described by RDF propertiese.g.

• author

• date created, date modified

• context (specific location within annotated doc)

• body (the “text” of the annotation)

• type (e.g. Comment, Example, Explanation, …)

Model of an Annotation Instance

Annotations and Meaning

• Present: annotators define personal/group/ task/community annotation types using an RDF Schema

• each type means whatever its definer wishes it to mean, but that meaning is advertised in the Web

• Future: annotators define personal/…/ community properties using RDF Schema or Web Ontology Language

An Annotea Use Case: WAI

• WAI (Web Accessibility Initiative) Evaluation and Repair Tool

• ERT property definitions are created that are specialized to this task

• Annotations include task-specific properties identifying the WAI guidelines that a document fails to meet...

… use case: WAI

• ERT annotations can be created by a human expert or by an automated evaluation tool

• ERT annotations can be evaluated by a human (a document author) and by automated repair tools

• Document author can augment the annotation to communicate state to reviewers and to other tools

Schema Additions for WAI task

problem

Marja

2000-01-10T17:20Z

dc:date

rdf:type

a:created

2000-01-10T17:20Z

a:annotates

dc:creator

XDoc.html

4GVF1D818 a:context

EARLeval

OHFR427

rdf:subclassAnnotation

WCAGCP 1.2

“non spacer IMG with equivalent ALT -- MANUAL –”

checkpoint

explanation

Adding Logic and Rules

• Common case:http://www.w3.org/2001/10/daml+oil#samePropertyAs

“for samePropertyAs(P, R), read P is an equivalent property to R.”

Equivalence (Synonyms)

samePropertyAs

equivalentTo

subClassOf

Formulae

• http://www.w3.org/2000/10/swap/log#• semantics

“This connects a document and the formula it parses to.”

• forAll• forSome• implies• . . .

cwm - Logic Processor

• Forward chaining inference engine

• Implements some first-order logic properties for expressing rules in RDF

i.e. those in http://www.w3.org/2000/10/swap/log#

WAI proto- rule

• “X annotates document_D, X has type EARL:Evaluation, X has EARL:Assertor P, P has WAIcredentials WAIexpert, P asserts R, R has predicate EARL:Fails R has object TestCase_C”implies “X fails TestCase_C”

Further Information

• Annoteahttp://www.w3.org/2001/Annotea

• cwmhttp://www.w3.org/2000/10/swap/

• Semantic Webhttp://www.w3.org/2001/sw/

• RDF & Web Ontology Languagehttp://www.w3.org/2001/sw/WebOnt/