Transcript Something about Semantic Web

Preserving Semantics in the Web
Ralph R. Swick
MIT LCS & W3C
[email protected]
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 properties
e.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
rdf:subclass
Annotation
EARLeval
rdf:type
a:annotates
4GVF1D818
dc:creator
Marja
XDoc.html
a:context
problem
explanation
a:created
dc:date
OHFR427
2000-01-10T17:20Z
checkpoint
2000-01-10T17:20Z
“non spacer IMG
with equivalent ALT
-- MANUAL –”
WCAG
CP 1.2
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
subClassOf
equivalentTo
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
• Annotea
http://www.w3.org/2001/Annotea
• cwm
http://www.w3.org/2000/10/swap/
• Semantic Web
http://www.w3.org/2001/sw/
• RDF & Web Ontology Language
http://www.w3.org/2001/sw/WebOnt/