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An Extensible Approach for Modeling Ontologies in RDF(S). Steffen Staab, Michael Erdmann, Alexander Mädche, & Stefan Decker Research Group Knowledge Management Institute AIFB, University of Karlsruhe, & DB Group, Stanford University Lisbon, September 21, 2000. RDF(S). What is an Ontology?.

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an extensible approach for modeling ontologies in rdf s

An Extensible Approach for Modeling Ontologies in RDF(S)

Steffen Staab, Michael Erdmann, Alexander Mädche, & Stefan DeckerResearch Group Knowledge Management

Institute AIFB, University of Karlsruhe,

& DB Group, Stanford UniversityLisbon, September 21, 2000

what is an ontology

RDF(S)

What is an Ontology?
  • Light-weight Ontology
    • concepts, atomic types
    • is-a hierarchy among concepts
    • associations between concepts
  • Heavy-weight Ontology
    • cardinality constraints
    • taxonomy of relations
    • reified statements
    • Axioms / semantic entailments of various tastes
      • expressiveness (DL, propositional, horn, or first order logic, higher order)
      • inferences
tools for ontologies
Tools for Ontologies
  • Light-weight
    • uncontroversial
    • all Tools support light-weight
      • Protege, Stanford
      • OntoEdit, Karlsruhe
      • UML-Tools, several
  • Heavy-weight
    • no consensus yet
    • layering seems appropriate/necessary
the use of xml namespaces in rdf s
The use of XML Namespaces in RDF(S)
  • Distinguish between different modeling layers
  • Reuse and integrate existing schemata and applications
  • XML serialization of RDF(S)
odoc o
Odoc & O
  • Odoc: namespace for ontology documentation
  • O: namespace for modeling of ontological axioms
  • An actual ontology definition – http://ontoserver.aifb.uni-karlsruhe.de/schema/example.rdf
modeling ontology metadata using rdf dublin core
Modeling ontology metadata using RDF Dublin Core
  • Dublin Core Metadata element set comprises 15 elements ensuring a maximal level of generality and exchangeability.
  • Extention of Dublin Core http://ontoserver.aifb.uni-karlsruhe.de/schema/ontodoc
example
<?xml version=‘1.0’ encoding =‘ISO-8859-1’?>

<rdf:RDF xmlns: rdf = http://www.w3.org/1999/02/22-rdf-syntax-ns#

xmlns:dc = http://purl.oclc.org/dc

xmlns:odoc=“http://ontoserver.aifb.uni-karlsruhe.de/schema/ontodoc”>

<rdf: Description about = “”>

<dc: Title>an Example Ontology</dc:Title>

<dc:creator>

<rdf: Bag>

<rdf:li>Steffen Staab</rdf:li>

</rdf:Bag>

</dc:creator>

<dc:date>…

<dc:format>…

<dc:description>…

<dc:subject>…..

<odoc:url>

http://ontoserver.aifb.uni-karlsruhe.de/schema/example.rdf

</odoc:url>

<odoc:version>2.1</odoc:version>

<odoc:last_modification>2000-03-01</odoc:last_modification>

<odoc:ka_technique>semi-automatic text knowledge accquisition</odoc:ka_technique>

<odoc:ontology_type>domain ontology</odoc:ontology_type>

<odoc:no_concepts>24</ odoc:no_concepts >

<odoc:no_relations>23</ odoc:no_relations >

<odoc:no_axioms>11</ odoc:no_axioms >

<odoc:highest_depth_level>6</odoc:highest_depth_level>

</rdf:Description>

</rdf:RDF>

Example
modeling
Modeling

Ideal Modeling (WYMIWYG)

  • Modeling not constrained by any language
  • All appropriate epistemological primitives and modeling styles should be usable

Real Modeling

  • A particular language always restricts allowed primitives (modeling language)
  • A particular language is needed in applications(application language)

=> distinguish modeling language from final application language

translate

automatically

axioms
Axioms
  • For Semantic Web and DAML more than light-weight is needed!
    • Axioms
  • Framework for conceptual modeling of axioms
    • Ontology of axiom patterns
    • language specific axiom-schemata can work with that knowledge
  • Interoperability is an issue
    • RDF / RDFS seem appropriate

next

slide

next but

one slide

axiom patterns
Axiom Patterns
  • 1. Axioms for a relational algebra
      • (a) Reflexivity of relations
      • (b) Symmetry of relations
      • (c) Asymmetry of relations
      • (d) Transitivity of relations
      • (e) Inverse relations
      • (f) Irreflexivity of relations
      • (g) Antisymmetry of relations
  • 2. Composition of relations
  • 3. (Exhaustive) Partitions of Concepts
axiom patterns1
Axiom Patterns
  • 4. Axioms for subrelation relationships
  • 5. Axioms for part-whole reasoning [Winston 87] [Chaffin 92]
      • PhysicalPartOf
      • MemberOf
      • PortionOf
      • PhaseOf
      • FeatureOf
      • SubRegionOf
  • 6. Nonmonotonicity
  • 7. Axioms for temporal and modal contexts
  • 8. (General axioms (application specific, ad hoc))
slide15

A simple symmetry example.

  • A relation MarriedWith(such as used for “William is married with Susan”)
  • First-order predicate logic:

MarriedWith(X,Y)MarriedWith(Y,X)

a simple symmetry example
A simple symmetry example.
  • In F-Logic

Person:LivingBeing[MarriedWithPerson].

Man::Person.

  • William:Man[MarriedWithSusan]
  • A rule corresponding to 1 is given by 4

Y[MarriedWithX]  X[MarriedWithY]

a simple symmetry example1
A simple symmetry example.
  • We denote symmetry as predicate that holds for particular relations:

Symmetric(MarriedWith)

  • In RDF(S) this specification may easily be realized by a newly agreed upon class o:Symmetric

<o:Symmetric rdf:ID=“marriedWith”/>

  • Derive the implications of symmetry by a general rule

Y [RX]Symmetric(R) and X[RY]

slide18

subClassOf

rdfs:Resource

instanceOf

RDF/RDFSlayer and namespace

rdfs:Class

rdf:Property

o:Partition

o:Relation

o:Composition

o:Partonomic-

RolePropagation

ontology meta layerand namespace

o:isInverseRelationOf

o:PartOfRel

o:Asymmetric

o:Reflexive

o:Transitive

o:Irreflexive

o:Symmetric

appl:Organisation

o:secondComponent

o:firstComponent

appl:Person

o:composee

Application-specific

schema and namespace

appl:Man

appl:Woman

appl:fatherInLaw

appl:fatherOf

appl:marriedWith

appl:marriedWith

Application- specificactual data

http://www.foo.com/W.Smith

http://www.foo.com/S.Smith

appl:lastName

appl:lastName

appl:firstName

appl:firstName

William

Smith

Susan

Smith

example of composition of relations
Example of Composition of Relations

<o:Composition rdf:ID="FatherInLawComp">

<o:composee rdf:Resource="fatherInLawOf"/>

<o:firstComponent rdf:Resource="fatherOf"/>

<o:secondComponent rdf:Resource="marriedWith"/>

</o:Composition>

rdf:Class

rdfs:Property

o:Composition

o:Relation

Composition(fatherInLawOf, fatherOf, marriedWith).

o:IrreflexiveRel

forall R,Q,S,X,Y,Z X[R ->> Z] <-

Composition(R, Q, S) and

X[Q ->> Y] and

Y[S ->> Z].

o:secondComponent

o:composee

appl:marriedWith

o:firstComponent

forall X,Y,Z

X[fatherInLawOf ->> Z] <-

X[fatherOf ->> Y] and

Y[marriedWith ->> Z].

appl:fatherInLawOf

appl:fatherOf

general axioms
General Axioms
  • Two ways to approach
    • RDF(S) representation for a particular inferencing system
      • OIL
    • Representation that is more application specific
      • A practical choice for many application-specific axioms
ontoedit supports axiom classification
OntoEdit supports Axiom Classification

fatherInLawOf

fatherOf

marriedWith

ontology engineering using ontoedit
Ontology Engineering using OntoEdit
  • Interaction with the user on a conceptual level
  • Multiple views for concepts, relations and axioms
  • Multilinguality
  • Linkable to NLP domain lexicon
  • Exports ontology (incl. axioms) into several formats
      • F-Logic (main language)
      • RDF/RDFS
      • DTDs (as far as possible)
      • ORDB-Schema (as far as possible)
      • OIL (partially and in RDF)
      • UML/XMI (planned)
      • the DAML language (when specified ;-)
frame logic inference engine access
Frame-Logic Inference Engine Access

Automatically

Derived from

Axiom views

Pure F-Logic

Debugging Instances + Rule Debugging

fact dl engine interface
FaCT DL Engine Interface
  • Generate FaCT LISP KB (future: OIL)
  • Call FaCT Client, transform ontology on FaCT server
  • Ask server
flexible epistemological level

RDF/RDFS layer

and namespace

rdfs:Resource

subClassOf

instanceOf

rdfs:Property

rdf:Class

rdfs:ConstraintProperty

rdf:type

rdfs:subClassOf

rdfs:subPropertyOf

rdfs:domain

rdfs:range

XRDF

OIL

DAML

o:isInverseRelationOf

o:Relation

o:Composition

o:PartOfRel

o:ReflexiveRel

o:Partition

o:IrreflexiveRel

Ontological meta layer for kinds

of relations with own namespace

o:PhysicalPartOfRel

o:SymmetricRel

o:AsymmetricRel

o:MemberOfRel

o:TransitiveRel

o:SubRegionOfRel

Application

Flexible Epistemological Level

XRDF

OIL

DAML

conclusion
Conclusion
  • ‘‘No Method fits all‘‘
    • Different applications need
      • different representation languages
      • with their underlying reasoning services
    • Ontology development must be aware of this
      • conceptual modeling
      • mechanisms to access/integrate several ontologies
        • distributed on the web
        • identified by (XML-) namespaces