The Semantic Web

steelsquareInternet and Web Development

Oct 20, 2013 (3 years and 11 months ago)

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The Semantic Web
Professor James Hendler
http://www.cs.umd.edu/~hendler
Director, Semantic Web and Agent Technology
Maryland Information and Network Dynamics Laboratory
Knowledge is Power (Revisited):
The Semantic Web
Dr. Edward Feigenbaum Stanford Univ.
Dr. James Hendler, Univ of Maryland
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The Evolving Web
Web of
Knowledge
HyperText Markup Language
HyperText Transfer Protocol
Resource Description Framework
eXtensible Markup Language
Self-Describing Documents
Foundation of the Current Web
Proof, Logic and
Ontology Languages
Shared terms/terminology
Machine-Machine communication
1990
2000
2010
Based on Berners-Lee, Hendler; Nature, 2001
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Web “travel agents”
Query processed: 73 answers found
 Google
document search finds 235,312 possible page hits.
 Http://www…jp/JRTrains.html
claims the answer is 27
 Http://www…jp/subway.html
claims the answer is 12
 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.
 A computer program that can compute that number is offered by the Tokyo
Digital City information analysis, click here
to run program.
...
How many train lines are there in Tokyo?
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Beyond HTML: adding syntax
 Current languages attack this by adding syntactic data
handling abilities
 XML (eXtensible Markup Language)
 Extensible keyword set
 Solves syntactic inequalities between data formats
 DB 1 -> ADDRESS <- DB 2
 Useful for Data Sharing
 Not search
<!Element TITLE-BLOCK EMPTY>
<!ATTLIST TITLE-BLOCK Title #cdata required Subtitle #cdata
implied>
<Title-Block>
<title> Beyond HTML <title>
<subtitle> adding syntax </subtitle>
</title-block>
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Semantic Problems for XML
 Synonymy and polysemy
* <PERSON> vs. <INDIVIDUAL>
* is <SPIDER> an arachnid or software?
 Structural differences
<PERSON>
<NAME>John Smith</NAME>
</PERSON>
<PERSON>
<NAME><FNAME>John</FNAME><LNAME>Smith</LNAME></NAME>
</PERSON>
<PERSON NAME=“John Smith”>
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Knowledge on the web
The Web as “Information Space”
 It's Large and It Grows Fast
 Lack of Referential Integrity
 High Variety in Quality of Knowledge
 Diversity of Content
 Unknown/unpredictable Use Scenarios for the Knowledge
 Problems of Trust, No Single Authority
 Knowledge acquired, not engineered
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The SEMANTICWeb
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
computing
A “semantic” language that ties the information on a page
to machine readable semantics (ontology)
Many research efforts in the past
 SHOE (Maryland), Ontobroker(Karlsruhe),OWL(Washington Univ)
 Largely grows from past DARPA programs (I3, ARPI)
Beginning to transition
 US and EU govt funding; W3C SW activity
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What is an Ontology?
Catalog/
ID
General
Logical
constraints
Terms/
glossary
Thesauri
“narrower
term”
relation
Formal
is-a
Frames
(properties)
Informal
is-a
Formal
instance
Value
Restrs.
Disjointness,
Inverse, part-
of…
TAXONOMY
ONTOLOGY
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A number of organizations cooperating
Semantic Web Res. (EU)
W3C
DAML
www.w3.org/2001/SW
RDF
RDF-S
DAML+OIL
language
IST Research efforts
Ontoweb
Oil
Intl Workshops
EU W3C
Members/directors
(Dan Brickley, coord)
 US and EU Govt
funding
Both working closely
with W3C to create a
web standard
Works closely with EU
on international
acceptance
Joint tool development
in open source arenas
 Desire to include
more partners
Japan/Asia
Australia
E-Business emphasis
DARPA Agent
Markup Language
WebOnt
Military emphasis
Semantic Web
Activity
www.daml.org
DAML+OIL
(webont)
2002 govt investment: US = $20,000,000; EU 20,000,000
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www.daml.org
 Language Specifications
 DAML Newsletter (you can subscribe)
 Collection of web tools
 Ontology library
 140+ ontologies
 DAML crawler
 over 12,000 pages w/2,700,000+ DAML statements
 Web tracking software used for baselining DAML use
 About 1,500,000 hits in first year
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Web Ontology - status
 DAML+OIL ontology language released on World Wide Web
 Annotated “walkthrough”
 Examples
 Full definition
 RDFS = Resource Description Framework Schema
 Provides 100% mapping to XML
 Open discussion group run by W3C: www-rdf-logic@w3.prg
 Denotational (and axiomatic) Semantics published
 First formal semantics for a web language
 Proposal to W3C for standardization ongoing
 Web Ontology working group
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DAML Denotational Semantics (Hayes, Horrock, Patel-
Schneider)
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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]
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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].
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DAML Ontology: for computer
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The SemanticWEB
Before
* monolithic
* consistent
* fully shared
* logic-based
uses
uses
uses
uses
uses
uses
uses
uses
Distributed,partially mapped, inconsistent -- but very flexible!
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Communities of interest
Museum
Special Event
Sports
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A web of semantics
 Small communities define common semantics
 Technical Vocabularies abound
 Mission specific
 Technical jargons
 Shared values
 Larger communities form around shared terms
 Mapping and “articulation” become crucial
 Interoperability at web languages level
 Top-Down (AIA defines critical aircraft properties)
or bottom up (Oh, a “foxbat” is a Mig29)
 Business case for improving communication!
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US: DARPA and W3C
Working Together
 DAML is being built on existing web “standards”, by many of
the same people who developed them
 PI Team includes funding for MITand W3C researchefforts
in “Semantic Web Advanced Development” activity
 PI/Co-PI: Tim Berners-Lee, Ralph Swick, Dan Connolly
XML
Existing W3C Recommendation
RDF/RDF(S)
Existing W3C Recommendation
DAML+OIL
DAML-Services
DAML-Query/Rules
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Semantic Web
Notional Schedule
Now
Later
You are here
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DAML
Examples
 “Transparent” Markup
 Content-Based Search
 Service advertising
Reading “DAML”!
Using “DAML”!
Writing “DAML”!
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Going Beyond Text!
Query processed:
 A satellite image taken yesterday at 10 AM is available on the web at http://…
 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: …)
 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.
 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)
 A service entitled “commercial service for providing satelite images” is
advertised as becoming available in 2004. See http://…
for more
information
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Service Descriptions
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Web Logics
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Conclusions
 The Semantic Web is coming!
 Joint development between DARPA/EU/and W3C communities
 Languages and tools are available to play with
 Http://www.daml.org/
 W3C interest group available for those wishing to join the discussion
 Www-rdf-logic@w3c.org
(live or archived)
 Ongoing DoD and commercial projects
 Come join us
 Submit ontologies/marked up pages
 Develop tools or help test ours
 Get in on the next big thing early!