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					          Semantic Web
          Hieu Le, Nhung Nguyen, Mayssam

               UIUC - CS511 – Fall 2005

(lots of slides browed from: Deborah McGuinness, James Hendler,
  Stefan Decker, Mike Lowndes, Mehmet S. Aktas, Steve Cayzer)
               Roadmap
Motivation
Broad picture
Zoom in to current state
Zoom in closer to the future
The Holly Grail: A Killer App.
Discussion
Conclusion
   Today: Rich Information Source for Human
          Manipulation/Interpretation



 Human
                                       Human




Human
                                        Human
 Tomorrow: Rich Information Source for Agent
        Manipulation/Interpretation




Human
        Agent




                Agent
                 Doctor’s appointment
     “The Semantic Web”, Scientific American, May 2001


                                             Insurance Co.

                                                   Rating
              Mom                                    Provider sites
Physician’s Agent

  required        in-plan?
  treatment       close-by?
                 Specialist?
                                       Schedule appointment


                    Driving schedule

  Lucy’s Agent                               Pete’ Agent
               Roadmap
Motivation
Broad picture
Zoom in to current state
Zoom in closer to the future
The Holly Grail: A Killer App.
Discussion
Conclusion
      The Evolving Web
                                                             Web of
                                                            Knowledge



                              Proof, Logic and
                             Ontology Languages
DATA/PROGRAMS
                                                   Shared terms/terminology
                                                   Machine-Machine communication
                                                                 2010

            Resource Description Framework
             eXtensible Markup LanguageSelf-Describing Documents
                                                                 2000

                     DOCUMENTS
      HyperText Markup Language
      HyperText Transfer ProtocolFoundation of the Current Web
                                                                 1990
                                               Berners-Lee, Hendler; Nature, 2001
           Web Semantics




Semantic Web LayerCake (Berners-Lee, 99;Swartz-Hendler, 2001)
        Can’t we just use XML?
This is what a web-page in natural language
looks like for a machine
                 XML helps

XML allows “meaningful tags” to be added to
parts of the text


                                         < name >

< education>


                                     < CV >
    < work>


  < private >
XML      machine accessible meaning
    But to your machine,
    the tags look like this….


                                      name
                                    < name >

<education>
< education>


                                  CV
                                < CV >
    <work>
    < work>


  <private>
  < private >
Schemas take a step in the right
          direction
 Schemas help….




                  < CV >    …by relating
                  private   common terms
                            between documents
But other people use other schemas

    Someone else has one like this….



                                           name>
                                           < name >

<educ>
< education>


                                       < CV
                                       < CV >>
      <>
    < work>


  < private >
  <>
The “semantics” isn’t there




           < CV >
          private   …which don’t fit in
      KR provides “external”
      referents to merge on



                       nme
                                                          CV
                              work                         CV
                vate


                       educ          CV


                   ed
                   uc                     <educ     >
                                          < education >
                                                                 name   >
                                                                << name >




                                                            < CV >
                                                            < CV



SW languages add mappings                       <>
                                              < work >


                                            <  >>
                                            < private




And structure.
         Current Activities



                                                            We
                                                            are
                                                            here




Semantic Web LayerCake (Berners-Lee, 99;Swartz-Hendler, 2001)
               Roadmap
Motivation
Broad picture
Zoom in to current state
Zoom in closer to the future
The Holly Grail: A Killer App.
Discussion
Conclusion
          W3C Web Ontology Working Group
• Web Ontology Working Group in the W3C Semantic Web Activity
  aimed at “extending the semantic reach of current XML and RDF
  meta-data efforts. “
• History
   – DAML+OIL is submitted as a joint committee effort published as a
     W3C note .
   – W3C WG Announcement in November 2001 -
     http://lists.w3.org/Archives/Public/www-rdf-
     logic/2001Nov/0000.html
   – Weekly teleconferences started in November 2001
   – First Face to Face Meeting - New Jersey (Lucent), Jan ‘02; 2nd -
     Amsterdam April (W3C); 3rd - CA (Fujitsu/Stanford host) July; 4th
     in Bristol UK (HP Host) Oct.
   – Four Working Drafts to date
       • Requirements/Use cases - March 2002
       • 3 Technical Documents - July 2002 (Language renamed OWL)
                               Membership
•   Current Working Group includes over 50 members from over 30 organizations.
     – Chairs
         • J. Hendler, MIND Lab UMCP
         • G. Schreiber, Univ. of Amsterdam
     – Industry including:
         • Large companies - Daimler Chrysler, IBM, HP, Intel, EDS, Fujitsu, Lucent,
            Motorola, Nokia, Philips Electronics, Sun, Unisys
         • Newer/smaller companies - IVIS Group, Network Inference, Stilo
            Technology, Unicorn Solutions
     – Government and Not-For-Profits:
         • US Defense Information Systems Agency, Interoperability Technology
            Association for Information Processing, Japan (INTAP) , Electricite De
            France, Mitre, NIST
     – Universities and Research Centers:
         • University of Bristol, University of Maryland, University of Southamptom,
            Stanford University
         • DFKI (German Research Center for Artificial Intelligence),
            Forschungszentrum Informatik, Ontoweb
     – Invited Experts
         • Well-known academics from non-W3C members (Hayes, Heflin, Stein,
            Borden)
 The Semantic Stack and Ontology Languages

                                           B
                                                                          OWL Full

                                                DAML,                      OWL DL
                                                 OIL,
                                               DAML+OIL                   OWL Lite
     A                                                    RDF Schema

                                                                RDF


                                                   XML, XML Schema


     The Semantic Language Layer for the Web   From “The Semantic Web” technical report by Pierce



A = Ontology languages based on XML syntax
B = Ontology languages built on top of RDF and RDF Schema
Resource Description Framework (RDF)
                  -I
•   Resource Description Framework (RDF) is a
    framework for
describing and interchanging metadata (data describing the
    web
resources).


•   RDF provides machine understandable semantics for
    metadata.
This leads,
   – better precision in resource discovery than full text
        search,
   – assisting applications as schemas evolve,
   – interoperability of metadata.
Resource Description Framework (RDF)-
                   II

•       RDF has following important concepts

    –      Resource : The resources being described by RDF are
           anything that can be named via a URI.

    –      Property : A property is also a resource that has a name, for
           instance Author or Title.

    –      Statement : A statement consists of the combination of a
           Resource, a Property, and an associated value.


    Example: Alice is the creator of the resource http://www.cs.indiana.edu/~Alice.
The Dublin Core Definition Standard

•       RDF is dependent on metadata conventions for definitions.

•       The Dublin Core is an example definition standard which
        defines a simple metadata elements for describing Web
        authoring.

•       It is named after 1995 Dublin (Ohio) Metadata Workshop.

•       Following list is the partial tag element list for Dublin Core
        standard.
    –      Creator: the primary author of the content
    –      Date: date of creation or other important life cycle events
    –      Title: the name of the resource
    –      Subject: the resource topic
    –      Description: an account of the content
    –      Type: the genre of the content
    –      Language: the human language of the content.
                                   Example

   Alice is the creator of the resource http://www.cs.indiana.edu/~Alice.
                                             Property
           Resource
                                                                                      Property
                                                                                      Value
                                                   creator
                                                     =
                                     http://purl.org/dc/elements/1.1/creator
http://www.cs.indiana.edu/~Alice                                                           Alice


 • Property “creator” refers to a specific definition. (in this example by Dublin Core
  Definition Standard). So, there is a structured URI for this property. This URI makes this
  property unique and globally known.
 • By providing structured URI, we also specified the property value Alice as following.
  “http://www.cs.indiana.edu/People/auto/b/Alice”
                                                  Inspired from “The Semantic Web” technical report by Pierce



                                                                  AIST Meeting JPL, CA 2003
                                Example                          Why bother to use
                                                                 RDF instead of XML?


 Alice is the creator of the resource http://www.cs.indiana.edu/~Alice.


  <rdf:RDF xmlns:rdf=”http://www.w3c.org/1999/02/22-rdf-syntax-ns##”
                xmlns:dc=”http://purl.org/dc/elements/1.1”
                xmlns:cgl=”http://cgl.indiana.edu/people”>
  <rdf:Description about=” http://www.cs.indiana.edu/~Alice”>
            <dc:creator>
                      <cgl:staff> Alice </cgl:staff>
            </dc:creator>
  </rdf:RDF>

• Information in the graph can be modeled in diff. XML organizations. Human readers would
infer the same structure, however, general purpose applications would not.
•Given RDF model enables any general purpose application to infer the same structure.
                                             Inspired from “The Semantic Web” technical report by Pierce




                                                             AIST Meeting JPL, CA 2003
                          RDF Schema (RDFS )                     It resembles
                                                                 objected-oriented
                                                                 programming


•       RDF Schema is an extension of Resource Description Framework.
•       RDF Schema provides a higher level of abstraction than RDF.
    –      specific classes of resources ,
    –      specific properties,
    –      and the relationships between these properties and other resources can be
           described.
•       RDFS allows specific resources to be described as instances of more
        general classes.
•       RDFS provides mechanisms where custom RDF vocabulary can be
        developed.
•       Also, RDFS provides important semantic capabilities that are used by
        enhanced semantic languages like DAML, OIL and OWL.




                                                        AIST Meeting JPL, CA 2003
              Limitations of RDF/RDFS

• No standard for expressing primitive data types such as integer, etc.
  All data types in RDF/RDFS are treated as strings.

• No standard for expressing relations of properties (unique, transitive,
  inverse etc.)

• No standard for expressing whether enumerations are closed.

• No standard to express equivalence, disjointedness etc. among
  properties




                                               AIST Meeting JPL, CA 2003
            DAML, OIL and DAML+OIL - I

• RDF\RDFS define a framework, however they have limitations. There is a
  need for new semantic web languages with following requirements
       • They should be compatible with (XML, RDF/RDFS)
       • They should have enough expressive power to fill in the gaps in
          RDFS
       • They should provide automated reasoning support

• Ontology Inference Layer (OIL) and DARPA Agent Markup Language
  (DAML) are two important efforts developed to fulfill these requirements.

• Their combined efforts formed DAML+OIL declarative semantic language.




                                                 AIST Meeting JPL, CA 2003
      DAML, OIL and DAML + OIL - II
• DAML+OIL is built on top of RDFS.
     • It uses RDFS syntax.
     • It has richer ways to express primitive data types.

• DAML+OIL allows other relationships (inverse and transitivity) to be
  directly expressed.

• DAML+OIL provides well defined semantics, This provides followings:
     • Meaning of DAML+OIL statements can be formally specified.
     • Machine understanding and automated reasoning can be supported.
     • More expressive power can be provided.




                                                 AIST Meeting JPL, CA 2003
                                 Example
                                                          How is DAML+OIL is
                                                          different than RDF/RDFS?


Example: T. Rex is not herbivore and not a currently living species.
• This statement can be expressed in DAML+OIL, but not in RDF/RDFS
   since RDF/RDFS cannot express disjointedness.

• DAML+OIL provides automated reasoning by providing such expressive
  power.
    – For instance, a software agent can find out the “list of all the carnivores that
      won’t be any threat today” by processing the DAML+OIL data representation
      of the example above.
    – RDF/RDFS does not express “is not” relationships and exclusions.

                                                   From “The Semantic Web” technical report by Pierce




                                                         AIST Meeting JPL, CA 2003
       Web Ontology Language (OWL)
• Web Ontology Language (OWL) is another effort developed by the OWL
  working group of the W3Consorsium.
• OWL is an extension of DAML+OIL.
• OWL is divided following sub languages.
        • OWL Lite
        • OWL (Description Logics) DL
        • OWL Full – limited cardinality
• OWL Lite provides many of the facilities of DAML+OIL provides. In
  addition to RDF/RDFS tags, it also allows us to express equivalence,
  identity, difference, inverse, and transivity.
• OWL Lite is a subset of OWL DL, which in turn is a subset of OWL Full.




                                               AIST Meeting JPL, CA 2003
  A Note: Having an ontology is
           not enough

• The philosophy of WWW and SW is
  similar: decentralized
• Ontologies and data formats are different
  from sources to sources, time to time.

           Ontology matching
          Data Integration
  A Note: Having an ontology is
           not enough

• The philosophy of WWW and SW is
  similar: decentralized
• Ontologies and data formats are different
  from sources to sources, time to time.

           Ontology matching
          Data Integration
                        But will it fly?
• DAML+OIL is already the most used ontology language ever!!
   – http://www.daml.org (3.5M statements on 25,000 web pages)
• Gaining acceptance by web players
   – Semantic Web Track being offered at WWW 2002
   – 3x more people attended WWW2002 Developer Day on SW than
      attended KR
• Significant (international) Govt Support
   – US DARPA/NSF; EU IST Framework 5,6
   – Japan, Germany, Australia considering significant investments
   – US National Cancer Institute to publish cancer vocabulary in DAML+OIL
• Much New Startup activity (even in this economic climate)
• Many tools being developed
   – Many of them aimed at developers, not just AI literate types
               Roadmap
Motivation
Broad picture
Zoom in to current state
Zoom closer to the future
The Holly Grail: A Killer App.
Discussion
Conclusion
Moving to the future of the
           web




 Semantic Web LayerCake (Berners-Lee, 99;Swartz-Hendler, 2001)
Web Agents need Service
     Descriptions
Semantic Web Service
    Description
 - <daml:Class rdf:ID="CreateAcct">
    <rdfs:subClassOf
        rdf:resource="http://www. daml.org/services/daml-
        s/2001/10/Process.daml#AtomicProcess" />
   - <rdfs:subClassOf>
      - <daml:Restriction daml:cardinality="1">
         <daml:onProperty rdf:resource="#createAcctInfo" />
       </daml:Restriction>
    </rdfs:subClassOf>
   - <rdfs:subClassOf>
      - <daml:Restriction daml:cardinality="1">
         <daml:onProperty rdf:resource="#createAcctOutput" />
       </daml:Restriction>
    </rdfs:subClassOf>
  </daml:Class>
 - <rdf:Property rdf:ID="createAcctInfo">
    <rdfs:subPropertyOf
        rdf:resource="http://www. daml.org/services/daml-
        s/2001/10/Process.daml#input" />
    <rdfs:domain rdf:resource="#CreateAcct" />
    <rdfs:range rdf:resource="#AcctInfo" />
  </rdf:Property>
 - <rdf:Property rdf:ID="createAcctOutput">
    <rdfs:subPropertyOf
        rdf:resource="http://www. daml.org/services/daml-
        s/2001/10/Process.daml#output" />
    <rdfs:domain rdf:resource="#CreateAcct" />
    <rdfs:range rdf:resource="#CreateAcctOutputType" />
</rdf:Property>
Services need Web Logics
                    Web of Trust
• Claims can be verified if there is supporting
  evidence from another (trusted) source
   – We only believe that someone is a professor
     at a university if the university also claims that
     person is a professor, and the university is on
     a list I trust.
     believe(c1) :- claims(x, c1) ^ predicate(c1, professorAt) ^
                     arg1(c1, x) ^ arg2(c1, y) ^ claims(c2, y) ^
                     predicate(c2, professorAt) ^ arg1(c2, x) ^
                     arg2(c2, y) ^ AccreditedUniversity(y)
     AcknowledgedUniversity(u) :- link-from(“http://www.cs.umd.edu/university-list”,u)



                           Notice this one
               Roadmap
Motivation
Broad picture
Zoom in to current state
Zoom closer to the future
The Holly Grail: A Killer App.
Discussion
Conclusion
 FOAF:a semweb case study

The Friend of a Friend
(FOAF) project is about
creating a Web of
machine-readable
homepages describing
people, the links between
them and the things they
create and do.

Distributed RDF/XML
records describing
people, who they know,
projects they work on…
       FOAF - motivations
• Augment e-mail filtering by prioritizing
  mails from trusted colleagues
• Locate people with interests similar to
  yours
• ‘Find an expert’ in knowledge
  communities
• Social network analysis
• Photo co-depiction
A simple foaf model

                   foaf:Person

     rdf:type



      foaf:name
                    Michael Souris


   foaf:mbox

                  mailto:mm@example.com
.. which can be serialized in
            XML

<rdf:RDF
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:foaf="http://xmlns.com/foaf/0.1/">

  <foaf:Person>
    <foaf:name>Michael Souris</foaf:name>
    <foaf:mbox rdf:resource="mailto:mm@example.com" />
  </foaf:Person>

</rdf:RDF>
So what?
           We need more!
• The history of WWW is a lesson
• We see the potential, but:
  – How to convince people to mark up their
    pages?
  – How to convince organization to export their
    data in SW formats?


      Answer: We need a Killer Application
           We need more!
• The history of WWW is a lesson
• We see the potential, but:
  – How to convince people to mark up their
    pages?
  – How to convince organization to export their
    data in SW formats?


      Answer: We need a Killer Application
     Semantic Web Challenge:
          Minimum Requirements
• First, the information sources used
  – should be geographically distributed,
  – should have diverse ownerships (i.e. there is no
    control of evolution),
  – should be heterogeneous (syntactically, structurally,
    and semantically), and
  – should contain real world data, i.e. are more than toy
    examples.
• Second, it is required that all applications
  assume an open world, i.e. assume that the
  information is never complete.
• Finally, the applications should use some formal
  description of the meaning of the data.
      Semantic Web Challenge:
                More Requirements
• The application uses data sources for other purposes or
  in another way than originally intended
• Using the contents of multi-media documents
• Accessibility in multiple languages
• Accessibility via devices other than the PC
• Other applications than pure information retrieval
• Combination of static and dynamic knowledge (e.g.
  combination of static ontologies and dynamic work-flows)
• The results should be as accurate as possible (e.g. use
  a ranking of results according to validity)
• The application should be scalable (in terms of the
  amount of data used and in terms of distributed
  components working together)
  For short, a Killer Application
         must provide:
1. A service that is not possible or practical
   under more traditional technologies,
2. Some clear benefit to developers, data
   providers, and end users with minimum
   extra costs
3. an application that becomes
   indispensable to a user-base much wider
   than the SW researchers community.
               Roadmap
Motivation
Broad picture
Zoom in to current state
Zoom closer to the future
The Holly Grail: A Killer App.
Discussion
Conclusion
    How do you think?


• Semantic web: Make the web
   become a huge distributed
           database
               Roadmap
Motivation
Broad picture
Zoom in to current state
Zoom closer to the future
The Holly Grail: A Killer App.
Discussion
Conclusion
                      Conclusion
• It is no longer a question of whether the semantic web will come
  into being, it is already here!
• We’re already well past the starting gate
    – Web ontologies, term languages, “shims” to DB and services,
       research in proofs/rules/trust
    – Standardization providing a common denominator for KR
       researchers as well as web developers
    – Small companies starting to form, Big companies starting to
       move
• Challenges ahead:
    – Ontology mapping
    – Data Integration
    – Finally, a Killer Application
Thanks
       On the Web -- links are
              critical!
       Web page                             Any Web Resource



       <a href=                                 URI>

HTML                  <a href=“http://…”>

 On the Semantic WEB -- links are critical!
                            URI


          URI                                    URI

RDF               RDF is like the web! And…
      RDF graphs resemble
         semantic nets
DOC1
    <mind:Person rdf:id=“Hendler”>
       <mind:title jobs:Professor>
       <jobs:placeOfWork http://www.cs.umd.edu>
    </mind:Person>



  Mind:                              Jobs: Professor

           DOC1             Mind:title

  Jobs:           Hendler
                       Jobs:placeOfWork          Web Page
                                               http://www…
        Semantics on the                                 WEB
• RDF, like the WWW itself, is not “separable”
   – Thinking about the ontologies, without considering
       • The links to other terms
       • The instances that link to them
       • The crawling and collecting of ontological terminologues
     Is like thinking about the Web without the links!!
                                                                      Other
                                                                    Professors
                                Other
                                titles            Jobs: Professor
     Mind:                                                                 Other
Other                                                                      Pages
                  DOC1                   Mind:title
URIs
     Jobs:                Hendler
                                  Jobs:placeOfWork            Web Page
                                            Other           http://www…
                                         descriptions
  Radically new view of Semantics

    = some partial mapping



                                                     uses
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   uses
    uses
      uses
       uses         uses
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                       uses                                       uses
                          uses                                     uses
                           uses
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                               uses                  uses
                                                       uses
uses                            uses                    uses
 uses                             uses
                            uses uses                    uses
  uses                        uses                        uses
                                                            uses
   uses                        uses
     uses
     Distributed,partially mapped, inconsistent -- but SCALEABLE!
      uses                       uses
                                  uses
                                   uses

				
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