Preserving Semantics in the Web

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22 Οκτ 2013 (πριν από 3 χρόνια και 11 μήνες)

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Preserving Semantics in the Web

Ralph R. Swick

MIT LCS & W3C

swick@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 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

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:subclass




Annotation

WCAG

CP 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


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/