CS690L Semantic Web and Knowledge Discovery: Concept, Technologies, Tool

1
CS690LSemantic Web and Knowledge Discovery
Concept, Technologies, Tool

• Yugi Lee
• STB 555
• [phone]
• leeyu_at_umkc.edu
• www.sice.umkc.edu/leeyu
• This presentation was designed based on
• Richard Fikess tutorial on Ontologies and
  Semantic Web.

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Semantic Web Language

• XML
• Language for describing the structure of document
  content e.g., declare data to be a retail price,
  a sales tax, a book title, ...
• Uniform method for describing and exchanging data
  using HTTP
• Provides a syntactic schema
• ltPublication URL "ftp//db.stanford xml.psgt
• ltTitlegt From Semistructured Data ... Language
  lt/Titlegt
• ltAuthorgt R. Goldman lt/Authorgt
• ltPublishedgt Proceedings of ... Databases
  lt/Publishedgt
• ltLocationgt Location of
  what?
• ltCitygt Philadelphia lt/Citygt
• ltStategt Pennsylvania lt/Stategt
• lt/Locationgt
• ltDategt
• ltMonthgt June lt/Monthgt
• ltYeargt 1999 lt/Yeargt
• lt/Dategt
• lt/Publicationgt

When in June?
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Semantic Web Language

• XML Is Not Enough
• Ontologies enable independently developed
  programs to exchange data XML provides
  syntactic schema
• Ontologies specify intended meaning in a computer
  interpretable form XML provides no means of
  specifying intended meaning of tags
• XML is like HTML, where you make up your own
  tags.
• But in XML, you cant say what your tags mean.

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W3C Semantic Web Activity

• Semantic Web Activity (http//www.w3.org/2001/sw/)
  
• Established to serve a leadership role, in both
  the design of enabling specifications and the
  open, collaborative development of technologies
  that support the automation, integration and
  reuse of data across various applications.
• Successor to the W3C Metadata Activity
• RDF Core Working Group (http//www.w3.org/2001/sw/
  RDFCore/)
• Responsible for the Resource Description
  Framework (RDF)
• Web Ontology Working Group (http//www.w3.org/2001
  /sw/WebOnt/)
• Charter Build upon the RDF Core work a language
  for defining structured web based ontologies
  which will provide richer integration and
  interoperability of data among descriptive
  communities
• Developing Ontology Web Language (OWL) Based on
  DAMLOIL, developed in DARPAs Agent Markup
  Language program

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Resource Description Framework (RDF)

• A simple representation language for describing
  Web resources
• All sentences are triples of the form (Property
  Subject Object)
• Property is a binary relation
• Subject is a URI reference
• Object is either a URI reference or a literal
• E.g., (creatorOf http//www.w3.org/Lassila Ora
  Lassila)
• XML external syntax, Model theoretic semantics
• Includes a resource Class and properties
  type, subclassOf, etc.
• Supports classes of resources and literals (type
  Elephant Clyde)
• Supports subclass hierarchies (subclassOf
  Elephant Mammal)
• Like a primitive frame representation language

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RDF Ontology

• Classes
• Resource
• Property
• Literal
• Statement
• Container
• Bag
• Seq
• Alt

• Properties
• type
• subject
• predicate
• object

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RDF Schema

• An ontology added to RDF
• Classes
• Class
• ContainerMembershipProperty

• Properties
• subClassOf
• subPropertyOf
• seeAlso
• isDefinedBy
• comment
• label
• range
• domain
• member

Resource
Literal
Class
Property
Container
Statement
ContainerMembershipProperty
Bag
Seq
Alt
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RDF-S Class and Property Definitions
ltrdfClass ID"MotorVehicle"gt
ltrdfssubClassOf rdfresource"http.../PR-rdf-sche
ma-19990303Resource"/gt lt/rdfClassgt ltrdfClass
ID"PassengerVehicle"gt ltrdfssubClassOf
rdfresource"MotorVehicle"/gt lt/rdfClassgt ltrdfC
lass ID"Van"gt ltrdfssubClassOf
rdfresource"MotorVehicle"/gt lt/rdfClassgt ltrdfC
lass ID"MiniVan"gt ltrdfssubClassOf
rdfresource"Van"/gt ltrdfssubClassOf
rdfresource"PassengerVehicle"/gt
lt/rdfClassgt ltrdfProperty ID "registeredTo"gt
ltrdfsdomain rdfresource MotorVehicle /gt
ltrdfsrange rdfresource Person
/gt lt/rdfPropertygt
Christine is a passenger vehicle. Is Christine a
motor vehicle? Yes.
Christine is registered to Arnie. What is
Arnie? A person.
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Comments on RDF and RDF-S

• Severely lacking in expressive power
• Domain and range constraints rather than
  Value-Type
• E.g., cant define class of people all of whose
  children are male
• No cardinality constraints
• Particularly important for exactly 1 and at
  most 1
• No decompositions
• Particularly important for disjoint and
  exhaustive
• No axioms
• No negation (!)
• Not useful for checking consistency
• E.g., cant prove an object is not an instance of
  a class
• Basically a typing system

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The DAML Program

• DAML DARPA Agent Markup Language
• Defense Advanced Research Agency (DARPA) program
• Program Managers James Hendler, Murray Burke
• Begin in August 2000
• Goal achieve semantic interoperability between
  Web pages, databases, programs, and sensors
• Integration contractor and 16 technology
  development teams
• MIT (Tim Berners-Lee, Ben Grosof)
• Stanford (Gio Weiderhold, Richard Fikes, Deborah
  McGuinness)
• UMBC (Tim Finin)
• U West Florida (Pay Hayes)
• Yale (Drew McDermott)

• Web site http//www.daml.org/

• Cycorp (Doug Lenat)
• Nokia (Ora Lassila)
• Teknowledge (Bob Balzer)

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DAMLOIL

• A representation language for user-defined
  ontologies
• An ontology added to RDF and RDF-Schema
• Specification document
• http//www.daml.org/2000/12/damloil-index.html
• Expressive power analogous to
• Description logics (e.g., CLASSIC)
• Monotonic frame languages (e.g., OKBC knowledge
  model)
• Designed in collaboration with the European
  Community
• Designers of the Ontology Inference Layer (OIL)
• Basis for OWL, the candidate W3C standard

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DAMLOIL Classes
Thing Restriction List Ontology AbstractProperty T
ransitiveProperty DatatypeProperty UniqueProperty
UnambiguousProperty Nothing
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DAMLOIL Properties

• Classes
• disjointWith
• Defining Non-primitive classes
• unionOf, disjointUnionOf, intersectionOf,
  complementOf, oneOf
• Restrictions
• onProperty, toClass, hasValue, hasClass,
  hasClassQ
• minCardinality, maxCardinality, cardinality
• minCardinalityQ, maxCardinalityQ, cardinalityQ

• Equivalence
• equivalentTo, sameClassAs, samePropertyAs
• Lists
• first, rest, item
• Properties
• inverseOf
• Ontologies
• versionInfo, imports

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Property Restrictions on Classes
ltClass ID "Person"gt ltcommentgt Person is a
subclass of objects whose parents are persons.
lt/commentgt ltrdfssubClassOfgt
ltdamlRestrictiongt ltdamlonProperty
rdfresource hasParent /gt
ltdamltoClass rdfresource Person /gt
lt/damlRestrictiongt lt/rdfssubClassOfgt ltcomment
gt Person is a subclass of resources that have
one father. lt/commentgt ltrdfssubClassOfgt
ltdamlRestrictiongt ltdamlonProperty
rdfresource hasFather /gt
ltdamlcardinalitygt 1 lt/damlcardinalitygt
lt/damlRestrictiongt lt/rdfssubClassOfgt
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Comments on DAMLOIL and OWL

• Expressive power of a description logic
• Representation language for both classes and
  instances
• Additional expressive power needed (at least FOL)
• No rationale for excluding any axiom from an
  ontology that is
• Not a tautology
• Satisfied by the intended interpretation of the
  ontology
• Example of need for additional expressive power
• The magnitude of a physical quantity in a given
  unit of measure
• (gt (AND (Quantity-Magnitude ?q ?u ?m)
  (Quantity-Dimension ?q ?d))
• (AND (type Physical-Quantity ?q) (type
  Unit-Of-Measure ?u)
• (type Magnitude ?m)
  (Unit-Dimension ?u ?d)))
• May be too difficult for the Web community to
  understand
• Acceptance will be depend on user-friendly tools
• Ok to support development of Semantic Web
  technology