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Understanding Ontology for Semantic Web Applications

This article explores the concept of ontology, its elements and application in Semantic Web. It covers RDF, OWL, object-oriented features, and the use of ontology in consumer products. Learn about ontology language and its benefits in encoding complex information. Discover how semantics play a crucial role in defining relationships between objects, classes, and properties within a given domain. Enhance your knowledge of ontology with practical examples and references for further exploration.

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Understanding Ontology for Semantic Web Applications

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  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 • Person can recognize the object by semantics Semantic 木 Tree 나무 Object Symbol

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

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

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

  7. Class Relationship Properties Elements of an ontology (1/3) • 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 • Is a formal language used to encode the ontology OWL CycL KIF • Developed as a follow-on from RDF and RDFS, as well as earlier ontology language projects including OIL, DAML and DAML+OIL. • First-order predicate calculus with some higher-order extensions • Syntax for • first-order logic that is based on • S-expressions

  11. A.I. Ubiquitous Computing Information Integration Semantic Web 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

  12. Manufacturer Mfr No. Shape Size (in) Price ($US) … Catalog No. Shape Size (in) Price ($US) … E-Machina 550296 Round 1.5 .35 Part No. Geom. Diam (mm) Price ($US) … iMetal Corp. XAB023 Round 1.5 .75 XAB023 Round 1.5 .75 550296 R 37 .35 E-Machina 550298 Square 1.25 .45 XAB035 Square 1.25 .25 iMetal Corp. XAB035 Square 1.25 .25 550298 S 31 .45 Supplier B Supplier A Example of Using ontology Ontology Washer Catalog No. Shape Size Price Buyer

  13. Applying area of ontologySemantic 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. XML Schema RDF OWL RDF Schema Data Layer - Simple data model and Syntax for metadata - RDF: Instances Logical Layer - Formal semantic - Reasoning support - Heavyweight ontologies Schema Layer - Definition of vocabulary - Lightweight ontologies Elements of a semantic web Higher Semantics Semantics Structure & Syntax

  15. Higher Semantics Semantics Structure & Syntax Layer of Elements

  16. Semantic Web Scenario 1 Reconstruction reconstructs Site has Feature Pertains to has Issue instance Historic event http://tes.htm Instance of Reconstruction issue http://dlib.etc.ucla.edu/Forum http://dlib.etc.ucla.edu/issue/roof Roof construction http://dlib.etc.ucla.edu/Forum/Curia

  17. Curia Iulia potentially describes includes North sector of Forum Page1 http://test1.html describes includes Arch of Forum describes Page2 http://test2.html Semantic Web Scenario 2

  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 metadataFind Things in the Real World Library Video shop Phone book Book’s location Video’s name Phone number of Pizzahut • Author • Title • Subject • ISDN • … • Actor’s name • Director’s name • Genre • … • Name • Location • …

  20. About metadataCommon 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 metadataSearching 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 Object Predicate Article(http://bluewater.tistory.com/16) Authored_by Byunggul Koh

  24. http://bluewater.tistory.com/16 http://bluewater.tistory.com Authored_by Name nationality Byunggul Koh Korea Graph representation of RDF Subject Predicate Object http://bluewater.tistory.com/16 Byunggul Koh Authored_by

  25. RDF vs. XML

  26. Serialization Syntaxes: RDF/XML

  27. Serialization Syntaxes: Notation 3

  28. ApplicationRDF Site Summary (RSS) • Publishing information about updates of a web page • RDF Site Summary (RSS1.0) • Based on RDF • Really Simple Syndication (RSS 2.0) • Based on XML & XML Schema

  29. ApplicationRDF 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 rdfs:Resource rdfs:subClassOf rdfs:subClassOf rdfs:subClassOf rdf:Property rdfs:type eg:Document eg:author eg:Person rdfs:domain rdfs:range rdf:type rdf:type eg:author http://example.com/Proposal/ eg:title eg:name Information Management-A Proposal Byunggul Koh

  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) <rdfs:Class rdf:ID="Person"> <rdfs:subClassOf rdf:resource="http://www.w3.org/1999/02/22-rdf-syntax-ns#Resource"/> </rdfs:Class> <rdfs:Class rdf:ID="Teacher"> <rdfs:subClassOf rdf:resource="#Person"/> </rdfs:Class> <rdf:Property rdf:ID="teacher"> <rdfs:domain rdf:resource="#Course"/> <rdfs:range rdf:resource="#Teacher"/> </rdf:Property> Person rdfs:subClassOf rdf:Property Teacher rdfs:subClassOf rdfs:range teacher rdfs:domain Course

  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 • Classification hierarchy • Simple constraint features OWL Lite OWL DL OWL Full Appendix • Maximum expressiveness without losing computational completeness • Maximum expressiveness and the syntactic freedom • No computational guarantees

  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) <owl:Class rdf:ID="Wine"> <rdfs:subClassOf rdf:resource="PotableLiquid"/> <rdfs:label xml:lang="en">wine</rdfs:label> <rdfs:label xml:lang="fr">vin</rdfs:label> ... </owl:Class>

  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) <owl:ObjectProperty rdf:ID="hasColor"> <rdfs:subPropertyOf rdf:resource="#hasWineDescriptor"/> <rdfs:range rdf:resource="#WineColor" /> ... </owl:ObjectProperty>

  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:Class rdf:ID=“Vehicle"> <owl:equivalentClass rdf:resource=“Car"/> </owl:Class> <Wine rdf:ID="MikesFavoriteWine"> <owl:sameAs rdf:resource="#StGenevieveTexasWhite" /> </Wine> Car Wine owl:equivalentClass rdf:type rdf:type Vechicle MikesFavoriteWine StGenevieveTexasWhite rdf:type Equus Same instances

  45. Object-Oriented Features in OWL (7/8) <owl:Class rdf:ID="WhiteBurgundy"> <owl:intersectionOf rdf:parseType="Collection"> <owl:Class rdf:about="#Burgundy" /> <owl:Class rdf:about="#WhiteWine" /> </owl:intersectionOf> </owl:Class> Burgundy White Wine

  46. Object-Oriented Features in OWL (8/8) <owl:Class rdf:ID="Fruit"> <owl:unionOf rdf:parseType="Collection"> <owl:Class rdf:about="#SweetFruit" /> <owl:Class rdf:about="#NonSweetFruit" /> </owl:unionOf> </owl:Class> SweetFruit NonSweetFruit 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 http://www.w3.org/TR/sw-oosd-primer/, 2006 • Asuncion Gomez-Perez et al., "Ontological Engineering," Springer, 2004 • OWL Web Ontology Language Use Cases and Requirements, http://www.w3.org/TR/webont-req/ • OWL Web Ontology Language Overview, http://www.w3.org/TR/owl-features/ • RDF Primer, http://www.w3.org/TR/rdf-primer/ • Ontology, Wikipedia • Overview of Ontology, SNU IDB Lab., 2006 • Overview of RDF, SNU IDB Lab., 2006

  50. Appendix

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