1 Object-Orientation in Ontology Date: April 30, 2007 Byunggul Koh Taeksu Kim

2 Contents  Ontology Overview  Definition  Elements of Ontology  Semantic Web  Consumer products  Ontology Language  RDF  RDF Schema  Object Oriented Features in RDF  OWL  Object Oriented Features in OWL  References & Appendix

3 Semantics Semantic Symbol Object  Person can recognize the object by semantics 木 Tree 나무

4 weak semantics strong semantics Is Disjoint Subclass of with transitivity property Logical Theory Thesaurus Has Narrower Meaning Than Taxonomy Is Sub-Classification of Conceptual Model Is Subclass of DB Schemas, XML Schema First Order Logic Relational Model, XML OWL RDF/S Semantic Expressivity

5 Logical Theory Thesaurus Has Narrower Meaning Than Taxonomy Is Sub-Classification of Conceptual Model Is Subclass of Is Disjoint Subclass of with transitivity property weak semantics strong semantics ER Semantic Expressivity Problem: Very General Semantic Expressivity: Very High Problem: Local Semantic Expressivity: Low Problem: General Semantic Expressivity: Medium Problem: Local Semantic Expressivity: High

6 Definition of ontology  In computer science Represents a set of concepts within a domain Relationships between those concepts

7 Elements of an ontology (1/3) ClassRelationship Properties  It need to specify descriptions for the following kinds of concepts:

8 Elements of an ontology (2/3)  Classes  Is abstract groups, sets, or collections of objects  May contain individuals, other classes, or a combination of both  Property  Objects can be described by assigning attributes to them  Has a name and a value,  Is used to store information that is specific to the object

9 Elements of an ontology (3/3)  Relationship  Property is to describe the relationships between objects  Relation is an property whose value is another object  Ex: Successor: Ford Explorer

10 Ontology Language OWL Developed as a follow-on from RDF and RDFS, as well as earlier ontology language projects including OIL, DAML and DAML+OIL. KIF Syntax for first-order logic that is based on S-expressions CycL First-order predicate calculus with some higher- order extensions  Is a formal language used to encode the ontology

11 Usage of an ontology  Tomorrow's applications can be "intelligent"  in the sense that they can more accurately work at the human conceptual level  Has many applying area Ubiquitous Computing Information Integration A.I. Semantic Web

12 Example of Using ontology SquareXAB RoundXAB023 …Price ($US) Size (in)ShapeCatalog No..4531S R … Price ($US) Diam (mm) Geom.Part No. Washer Catalog No. Shape Size Price iMetal Corp. E-Machina iMetal Corp. E-Machina Manufacturer Square Round RoundXAB SquareXAB035 …Price ($US)Size (in)ShapeMfr No. Supplier A Supplier B Buye r Ontology

13 Applying area of ontology Semantic web  Way of enabling the semantics to be used by web applications and intelligent agents  Standard  W3C  RDF  DAML-OIL  OWL  ISO/IEC  Topic maps

14 Elements of a semantic web HigherSemantics Semantics Structure & Syntax Logical Layer - Formal semantic - Reasoning support - Heavyweight ontologies Schema Layer - Definition of vocabulary - Lightweight ontologies Data Layer - Simple data model and Syntax for metadata - RDF: Instances OWL RDF Schema RDFXML Schema

15 Layer of Elements HigherSemantics Semantics Structure & Syntax

16 Semantic Web Scenario 1 Feature Reconstruction Issue instance Historic event Site has reconstructs Pertains to Instance of Reconstruction issue Roof construction

17 Semantic Web Scenario 2 Arch of Forum Curia Iulia North sector of Forum describes includes potentially describes Page1 Page2

18 Contents  Ontology Overview  Definition  Elements of Ontology  Semantic Web  Consumer products  Ontology Language  RDF  RDF Schema  Object Oriented Features in RDF  OWL  Object Oriented Features in OWL  References & Appendix

19 About metadata Find Things in the Real World LibraryVideo shopPhone book Author Title Subject ISDN … Book’s location Actor’s name Director’s name Genre … Video’s name Name Location … Phone number of Pizzahut

20 About metadata Common Thread in Find Things  Based on metadata  Information about information  E.g.  Finding information  Book’s location  Using information about information  Book’s title, author, etc.

21 About metadata Searching in WWW  The Web is a lot like a really big library  There is hardly any metadata on the Web  Search engine do the equivalent of going through the library, reading every book, and allowing us to look things up based on the words in the text.

22 Introduction to RDF  Resource Description Framework  Is W3C standard for encoding knowledge, for the web  A framework for supporting resource description, or metadata  Make the management and navigation of Web data easier

23 RDF Triple Subject Predicate Object Article( Authored_by Byunggul Koh

24 Graph representation of RDF Byunggul Koh Authored_by Byunggul KohKorea Authored_by Namenationalit y Subject Object Predicate

25 RDF vs. XML RDFXML SemanticsSyntax GraphTree Relation representation Data representation Simple syntax Great ScalabilityLack of scalability

26 Serialization Syntaxes: RDF/XML

27 Serialization Syntaxes: Notation 3

28 Application RDF Site Summary (RSS)  Publishing information about updates of a web page  RDF Site Summary (RSS 1.0)  Based on RDF  Really Simple Syndication (RSS 2.0)  Based on XML & XML Schema

29 Application RDF Site Summary (RSS)

30 RDF Schema  RDF specification  Extensible knowledge representation language intended to structure RDF resources  Provides basic elements for the description of ontology  Called RDF vocabularies

31 Example of RDF Schema eg:Documenteg:authoreg:Person Byunggul KohInformation Management-A Proposal eg:author eg:name eg:title rdfs:Resource rdf:Property rdfs:type rdfs:subClassOf rdfs:domainrdfs:range rdf:type rdfs:subClassOf

32 Object-Oriented Features in RDF (1/4)  rdfs:Resource  All things described by RDF are called resources  rdfs:Class  Declare a resource as a class for other resources  rdf:Property  The class of RDF properties  rdfs:subClassOf  Declare hierarchies of classes  rdfs:subPropertyOf  State that all resources related by one property are also related by another

33 Object-Oriented Features in RDF (2/4)  rdf:type  State that a resource is an instance of a class  rdfs:domain  Declares the class of the subject in a triple using this property as predicate  P rdfs:domain C  rdfs:range  Declares the values of a property are instances of one or more classes  P rdfs:range C

34 Object-Oriented Features in RDF (3/4) Person Teacher teacher rdfs:domain rdf:Property Course rdfs:range rdfs:subClassOf rdfs:subClassOf

35 Object-Oriented Features in RDF (4/4)  Classes in RDF  Class  Associations in RDF  Attributes in RDF  Property  Instances in RDF  Type  RDF has sufficient features for Object-Oriented paradigm Appendix

36 Contents  Ontology Overview  Definition  Elements of Ontology  Semantic Web  Consumer products  Ontology Language  RDF  RDF Schema  Object Oriented Features in RDF  OWL  Object Oriented Features in OWL  References & Appendix

37 What is OWL?  Web Ontology Language  Built on top of RDF  OWL is  Stronger language with greater machine interpretability than RDF  Greater vocabulary and stronger syntax than RDF  E.g. Inverse, Union, Intersection

38 Three Sublanguages OWL Lite OWL DLOWL Full Classification hierarchy Simple constraint features Maximum expressiveness and the syntactic freedom No computational guarantees Maximum expressiveness without losing computational completeness Appendix

39 Object-Oriented Features in OWL (1/8)  owl:Class  Class is a group of individuals that belong together because they share some properties  Individual  Individuals are instances of classes  rdfs:subClassOf  Class hierarchies may be created by making one or more statements that a class is a subclass of another class

40 Object-Oriented Features in OWL (2/8) wine vin...

41 Object-Oriented Features in OWL (3/8)  owl:ObjectProperty, owl:DatatypeProperty  Datatype properties  Relations between instances of classes and RDF literals and XML Schema datatypes  Object properties  Relations between instances of two classes.  rdf:Property  rdfs:subPropertyOf  Property hierarchies may be created by making one or more statements that a property is a subproperty of one or more other properties  rdfs:domain  A domain of a property limits the individuals to which the property can be applied  rdfs:range  The range of a property limits the individuals that the property may have as its value

42 Object-Oriented Features in OWL (4/8)...

43 Object-Oriented Features in OWL (5/8)  owl:equivalentClass  Two classes may be stated to be equivalent  owl:equivalentProperty  Two properties may be stated to be equivalent  owl:sameAs  Two individuals may be stated to be the same  owl:differentFrom  An individual may be stated to be different from other individuals  owl:intersectionOf  Intersections of named classes and restrictions  owl:unionOf  Arbitrary Boolean combinations of classes and restrictions

44 Object-Oriented Features in OWL (6/8) <owl:sameAs rdf:resource="#StGenevieveT exasWhite" /> Vechicle Car Equus owl:equivalentClass rdf:type Wine StGenevieveTexasWhiteMikesFavoriteWine rdf:type Same instances

45 Object-Oriented Features in OWL (7/8) White WineBurgundy

46 Object-Oriented Features in OWL (8/8) NonSweetFruitSweetFruit Appendix

47 Expression Power of OWL  OWL model can express  The disjoint of two classes  The intersection and complement of two classes  Minimum and maximum cardinality of the class  Symmetric, transitive, functional, and inverse-functional property of the class  Inverse relation of two property  Create equivalent classes which has different name

48 Contents  Ontology Overview  Definition  Elements of Ontology  Semantic Web  Consumer products  Ontology Language  RDF  RDF Schema  Object Oriented Features in RDF  OWL  Object Oriented Features in OWL  References & Appendix

49 References  W3C, A Semantic Web Primer for Object-Oriented Software Developers, available at oosd-primer/, 2006  Asuncion Gomez-Perez et al., "Ontological Engineering," Springer, 2004  OWL Web Ontology Language Use Cases and Requirements,  OWL Web Ontology Language Overview,  RDF Primer,  Ontology, Wikipedia  Overview of Ontology, SNU IDB Lab., 2006  Overview of RDF, SNU IDB Lab., 2006

50 Appendix

51 RDFS (1/3)  rdfs:Resource  rdfs:Class  rdfs:Literal  The class of literal values such as strings and integers  rdfs:Datatype  rdfs:Datatype is the class of datatypes  rdf:XMLLiteral  The class of XML literal values  rdf:Property

52 RDFS (2/3)  rdfs:range  rdfs:domain  rdf:type  rdfs:subClassOf  rdfs:subPropertyOf  rdfs:label  Instance of rdf:Property that may be used to provide a human- readable version of a resource's name  rdfs:comment  Instance of rdf:Property that may be used to provide a human- readable description of a resource

53 RDFS (3/3)  rdfs:Container  rdf:Bag  rdf:Seq  rdf:Alt  rdfs:ContainerMembershipProperty  rdfs:member  rdf:List  rdf:first  rdf:rest  rdf:nil  rdf:Statement  rdf:subject  rdf:predicate  rdf:object  rdfs:seeAlso  rdfs:isDefinedBy  rdf:value Back to p.34

54 OWL (1/3)  owl:AllDifferent  A number of individuals may be stated to be mutually distinct in one AllDifferent statement  owl:inverseOf  If the property P1 is stated to be the inverse of the property P2, P1(x,y) iff P2(y,x)  owl:allValuesFrom  If an instance of the class is related by the property to a second individual, then the second individual can be inferred to be an instance of the local range restriction class  owl:someValuesFrom  A particular class may have a restriction on a property that at least one value for that property is of a certain type

55 OWL (2/3)  owl:cardinality  Cardinality is provided as a convenience when it is useful to state that a property on a class has both minCardinality 0 and maxCardinality 0 or both minCardinality 1 and maxCardinality 1  owl:minCardinality  If a minCardinality of 1 is stated on a property with respect to a class, then any instance of that class will be related to at least one individual by that property  owl:maxCardinality  If a maxCardinality of 1 is stated on a property with respect to a class, then any instance of that class will be related to at most one individual by that property

56 OWL (3/3)  owl:one of  Classes can be described by enumeration of the individuals that make up the class  owl:hasValue  A property can be required to have a certain individual as a value  owl:disjointWith  Classes may be stated to be disjoint from each other  owl:unionOf  owl:intersectionOf  owl:complementOf Back to p.45

57 OWL Lite, OWL DL, OWL Full OWL LiteOWL DLOWL Full Following property can not be specified  owl:minCardinality  owl:maxCardinality  owl:cardinality  Only 0 or 1 can be used  owl:hasValue  owl:disjointWith  owl:oneOf  owl:complementOf  owl:unionOf Following property can not be specified  FunctionalProperty  InverseFunctionalProperty  owl:cardinality Can not use metaclass Can not import the OWL Full ontology All features in specification can be used NCA IV- RER-04059: A Research on Web Ontology Development Guideline, National Information Society Agency, Back to p.37