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The Semantic WebProfessor James Hendler

http://www.cs.umd.edu/~hendlerDirector, Semantic Web and Agent Technology

Maryland Information and Network Dynamics Laboratory

http://www.cs.umd.edu/~hendler

Knowledge is Power (Revisited):The Semantic Web

Dr. Edward Feigenbaum Stanford Univ.Dr. James Hendler, Univ of Maryland

4WI-2001: Maebashi, Japan

The Evolving WebWeb of

Knowledge

HyperText Markup LanguageHyperText Transfer Protocol

Resource Description FrameworkeXtensible Markup Language Self-Describing Documents

Foundation of the Current Web

Proof, Logic andOntology Languages Shared terms/terminology

Machine-Machine communication

1990

2000

2010

Based on Berners-Lee, Hendler; Nature, 2001


Web “travel agents”

Query processed: 73 answers foundu Google document search finds 235,312 possible page hits.u Http://www…jp/JRTrains.html claims the answer is 27 u Http://www…jp/subway.html claims the answer is 12u A database entitled “JRTLDB” can be queried for the answer, but you will

need “Japanese Railroad Access Code.” Click here for database access; click here for more information.

u A computer program that can compute that number is offered by the Tokyo Digital City information analysis, click here to run program.

u ...

How many train lines are there in Tokyo?


Beyond HTML: adding syntax

l Current languages attack this by adding syntactic data handling abilitiesu XML (eXtensible Markup Language)

l Extensible keyword setl Solves syntactic inequalities between data formats

u DB 1 -> ADDRESS <- DB 2l Useful for Data Sharing

u Not search

<!Element TITLE-BLOCK EMPTY> <!ATTLIST TITLE-BLOCK Title #cdata required Subtitle #cdataimplied><Title-Block>

<title> Beyond HTML <title><subtitle> adding syntax </subtitle>

</title-block>


Semantic Problems for XML

l Synonymy and polysemy* <PERSON> vs. <INDIVIDUAL>* is <SPIDER> an arachnid or software?

l Structural differences

<PERSON><NAME>John Smith</NAME>

</PERSON>

<PERSON><NAME><FNAME>John</FNAME><LNAME>Smith</LNAME></NAME>

</PERSON>

<PERSON NAME=“John Smith”>


Knowledge on the web

lThe Web as “Information Space”u It's Large and It Grows Fastu Lack of Referential Integrityu High Variety in Quality of Knowledgeu Diversity of Contentu Unknown/unpredictable Use Scenarios for the Knowledgeu Problems of Trust, No Single Authorityu Knowledge acquired, not engineered


The SEMANTIC Web

l The Semantic Web is based on languages that make more of the semantic content of the page available in machine-readable formats for agent-based computingu A “semantic” language that ties the information on a page

to machine readable semantics (ontology)lMany research efforts in the past

u SHOE (Maryland), Ontobroker(Karlsruhe),OWL(Washington Univ)u Largely grows from past DARPA programs (I3, ARPI)

lBeginning to transition u US and EU govt funding; W3C SW activity


What is an Ontology?

Catalog/ID

GeneralLogical

constraints

Terms/glossary

Thesauri“narrower

term”relation

Formalis-a

Frames(properties)

Informalis-a

Formalinstance Value

Restrs.

Disjointness, Inverse, part-

of…

TAXONOMY ONTOLOGY


A number of organizations cooperating

Semantic Web Res. (EU)

W3CDAML

www.w3.org/2001/SW

RDFRDF-S

DAML+OILlanguage

IST Research effortsOntowebOil

Intl Workshops

EU W3CMembers/directors

(Dan Brickley, coord)

l US and EU Govt fundingw Both working closely

with W3C to create a web standard

wWorks closely with EU on international acceptance

w Joint tool development in open source arenas

w Desire to include more partnersw Japan/Asia

w Australia

E-Business emphasis

DARPA Agent Markup Language

WebOnt Military emphasis

Semantic WebActivity

www.daml.org

DAML+OIL(webont)

2002 govt investment: US = $20,000,000; EU 20,000,000

http://www.w3.org/2001/SW

http://www.daml.org


www.daml.org

l Language Specificationsl DAML Newsletter (you can subscribe)l Collection of web toolsl Ontology library

u 140+ ontologies

l DAML crawler u over 12,000 pages w/2,700,000+ DAML statements

l Web tracking software used for baselining DAML useu About 1,500,000 hits in first year

http://www.daml.org


Web Ontology - status

l DAML+OIL ontology language released on World Wide Webu Annotated “walkthrough”u Examplesu Full definition

l RDFS = Resource Description Framework Schemal Provides 100% mapping to XML

u Open discussion group run by W3C: [email protected] Denotational (and axiomatic) Semantics published

l First formal semantics for a web languageu Proposal to W3C for standardization ongoing

l Web Ontology working group

mailto:[email protected]


DAML Denotational Semantics (Hayes, Horrock, Patel-Schneider)


DAML Axiomatic Semantics (Fikes, McGuiness)

1.1.2. rdfs:Class

This class is prefixed with “rdfs” to indicate that it is from the namespace http://www.w3.org/2000/01/rdf-schema# and to distinguish it from “Class” as defined in DAML+OIL.

%% No object can be both type “Property” and type “rdfs:Class” (i.e., properties and RDF-S classes are disjoint).(not (and (Type ?x Property) (Type ?x rdfs:Class))) [rdfs:Class axiom 1]

1.1.3. Literal

%% “Literal” is type “rdfs:Class”.(Type Literal rdfs:Class) [Literal axiom 1]

1.1.4. Statement

%% If an object ST is type “Statement”, then there exists a value of “predicate” for ST, a value of “subject” for ST, and a value of “object” for ST. (I.e., every statement has a predicate, subject, and object.)(=> (Type ?st Statement)

(exists (?p ?r ?o)(and (PropertyValue predicate ?st ?p)

(PropertyValue subject ?st ?r)(PropertyValue object ?st ?o)))) [Statement axiom 1]

http://www.w3.org/2000/01/rdf-schema#


DAML Ontology

:StepRule :a rdf:Property;rdfs:domain :ProofStep;rdfs:range :RuleName;restriction

[xsd:type “string”;maxcardinality: 1].

:StepDependsOn a rdfs:Property;rdfs:domain :ProofStep;rdfs:range [ :collectionOf :StepID].

:ResourceDescription a rdfs:class;

:TrustedResource a rdfs:class.

:TrustedLogic a rdfs:class.

:CompoundAssertion a rdfs:Class.

:AssertStep a rdf:property;rdfs:range CompoundAssertion;rdfs:Domain [ :CollectionOf :Assertion].


DAML Ontology: for computer


The Semantic WEB

Before

* monolithic

* consistent

* fully shared

* logic-based

uses

uses

uses

uses

usesuses

uses

uses

Distributed,partially mapped, inconsistent -- but very flexible!


Communities of interest

Museum

Special Event

Sports


A web of semantics

l Small communities define common semanticsu Technical Vocabularies abound

l Mission specificl Technical jargonsl Shared values

l Larger communities form around shared termsu Mapping and “articulation” become crucial

l Interoperability at web languages levell Top-Down (AIA defines critical aircraft properties)

or bottom up (Oh, a “foxbat” is a Mig29)l Business case for improving communication!


US: DARPA and W3CWorking Together

l DAML is being built on existing web “standards”, by many of the same people who developed theml PI Team includes funding for MITand W3C researchefforts in “Semantic Web Advanced Development” activity l PI/Co-PI: Tim Berners-Lee, Ralph Swick, Dan Connolly

XML Existing W3C Recommendation

RDF/RDF(S) Existing W3C Recommendation

DAML+OILDAML-ServicesDAML-Query/Rules


Semantic WebNotional Schedule

Now

Later

You are here


DAML Examples

l “Transparent” Markupl Content-Based Searchl Service advertising

Reading “DAML”! Using “DAML”!

Writing “DAML”!


Going Beyond Text!

Query processed:u A satellite image taken yesterday at 10 AM is available on the web at http://…u A new satellite image, to be taken today at 10AM, will be available for

$100 — click here to authorize transfer of funds and obtain image (you will need a valid credit card number from one of the following providers: …)

u In an emergency situation, a Coast Guard observer plane can be sent to any location within the area you indicate. Service Note: You will be responsible for cost of flight if the situation does not result in emergency pickup. Click Here for more information.

u A high altitude observer can be sent to your location in 13 hours. Click here to initiate procedure. (You will need to provide US military authorization, A valid military unit code, and the name of commanding officer)

u A service entitled “commercial service for providing satelite images” is advertised as becoming available in 2004. See http://… for more information


Service Descriptions


Web Logics


Conclusions

l The Semantic Web is coming!u Joint development between DARPA/EU/and W3C communitiesu Languages and tools are available to play with

l Http://www.daml.org/u W3C interest group available for those wishing to join the discussion

l [email protected] (live or archived)u Ongoing DoD and commercial projects

l Come join usu Submit ontologies/marked up pagesu Develop tools or help test ours

l Get in on the next big thing early!

http://www.daml.org/

mailto:[email protected]