The Semantic Web: The Roles of XML and RDF

1. The Semantic Web:The Roles of XML and RDF Presenter: Dong Han STEFAN DECKER AND SERGEY MELNIK FRANK VAN HARMELEN DIETER FENSEL AND MICHEL KLEIN, JEEN BROEKSTRA, MICHAEL ERDMANN, IAN HORROCKS

2. Overview • Ontology • XML & XML schema • RDF & RDF schema • Knowledge presentation • Using XML • Using RDF • OIL • Challenges

3. Ontology--What are ontologies? Ontologiesare content theories about the sorts of objects, properties of objects, and relations between objects that are possible in a specified domain of knowledge.

4. Ontology--What are ontologies? Formal, explicit specification of a sharedconceptualization Consensual knowledge Machine readable • The type of concepts, the relations between the concepts, and the constraints on their usage, are explicitly defined Abstract model of some phenomena in the world

5. Ontology--What are ontologies? • Defining concepts in the domain (classes) • Arranging the concepts in a hierarchy (subclass-superclass hierarchy) • Defining which attributes and properties (slots) classes can have and constraints on their values • Defining individuals and filling in slot values

6. Ontology Example

7. XML: eXtensibleMarkup Language <h2>Nonmonotonic Reasoning</h2> <i>by <b>V. Marek</b> and <b>M. Truszczynski</b></i><br> Springer 1993<br> ISBN 0387976892 USE of XML? Serialization syntax for other markup languages.(SMIL) Semantic markup of Web pages. Uniform data-exchange format. XML specifies data <book> <title>NonmonotonicReasoning</title> <author>V. Marek</author> <author>M. Truszczynski</author> <publisher>Springer</publisher> <year>1993</year> <ISBN>0387976892</ISBN> </book> extensible set of tags

8. XML Schema

9. RDF: Resource Description Framework • Object-Attribute-Value triple, commonly written as A(O,V). RDF Graphs

10. RDF Schema • Define vocabulary for RDF • Organise this vocabulary in a typed hierarchy • Class, SubClassOf, type • Property, subPropertyOf, • domain, range

11. Knowledge presentation Requirements for any exchange format? • Universal expressive power. • Syntactic interoperability. (parsing data) • Semantic interoperability. (defining mappings between terms within the data) XML vs RDF

12. Point-to-point communication with XML. 1.Domain model be encoded in XML. 2.Both parties must agree on a translation schema.

13. Multiple Ways encoded in XML (Owner)

14. Alignment of Conceptual Model using XML

15. Using RDF--Significant Advantages over XML • The OAV structure provides natural semantic units. • A domain model—defining objects and relationships – easy to translation. • Techniques for mapping two RDF are directly applicable.

16. Three-layered architecture of the Semantic Web OIL RDF Schema RDF

17. OIL as RDF(S) extension RDF(S) OIL

18. OIL : Ontology Inference Layer • Classes can be primitive ● elephant : animal that has-colorgrey • Classes can be defined ● vegetarian ⇔ person who eats neither meat nor fish • Classes allowed in slot constraints ● slot-constraint eats has-valuemeat (eats some meat) ● slot-constraint eatsvalue-typemeat(eats only meat)

19. Can use arbitrary class expressions instead of only class names ● slot-constraint eatsvalue-type NOT (meat OR fish) • Cardinality constraints can include value-types ● slot-constraint eatsmax-cardinality 1 plant • Supports sub-slot relation ● daughter-of sub-slot of child-of • Slot properties ● transitive (e.g., part-of ) ● symmetrical (e.g., connected-to)

20. Defining herbivore as subclass-ofanimal, NOTcarnivore

21. Challenges Expand this genericmethod for creating Web-enabled, special purpose knowledge representation languages.

22. Questions?

23. Thanks!