1. More RDF CS 431 – 20040310 Carl Lagoze – Cornell University Acknowledgements: Eric Miller Dieter Fensel

2. RDF Data Model Directed labeled graphs Model elements –Resource –Property –Value –Statement –Containers

3. RDF meta-model RDF basic types –rdf:Resource – everything that can be identified (with a URI) –rdf:Property – specialization of a resource expressing a binary relation between two resources –Rdf:type – predefined property to express that subject of property is considered to be an instance of that category or class defined by the value of the property –rdf:statement – a triple with properties rdf:subject, rdf:predicate, rdf:object An RDF statement is a triple consisting of a resource (subject), a property and a second resource (object) –(:s :p :o) Expressible also as binary relations –P(S,O) – e.g., Title(R, “War & Peace”)

4. Expressing Simple Binary Relations Resource:R1 Property:P1 Value Resource:R2 (:R1 :P1 :R2) P1(R1, R2) >

5. Expressing n-ary relations (“Carl Lagoze” “address” “301 College Ave, Ithaca, NY 14850”) (“Carl Lagoze” “address” “301 College Ave” “Ithaca” “NY” “14850”) street city statezip address “301 College Ave”“Ithaca” “NY” “14850” “blank node” URI 1

6. Another n-ary relation example

7. Expressing Collection Primitives in Binary Relations

8. Reification Structure Staff member 85740 said the weight of item 10245 is 2.4 units

9. Reification XML

10. RDF Schemas Declaration of vocabularies –properties defined by a particular community –characteristics of properties and/or constraints on corresponding values Provides substructure for inferences based on existing triples Schema language is an expression of basic RDF model Schema Type System - Basic Types –Property, Class, SubClassOf, Domain, Range –Minimal (but extensible) at this time –Expressible in the RDF model and syntax

11. Schema Vocabularies Enables communities to share machine readable tokens and locally define human readable labels. dc:Creator “Nom” rdfs:label “Author” rdfs:label “$100 $a” rdfs:label

12. Relationships among vocabularies dc:Creator ms:director marc:100 bib:Author

13. Relationships among vocabulary elements URI:R “John Smith” ms:director dc:Creatorms:director rdfs: subPropertyOf rdfs:label “Director” dc:Creator

14. RDF Schema: Specializing Properties rdfs:subPropertyOf – allows specialization of relations –E.g., the property “father” is a subPropertyOf the property parent subProperty semantics

15. Sub-Property Semantics

16. Constraints on Properties Force objects to be of a certain type rdfs:domain –Restricts the type of resources that may have a specific property rdfs:range –Restricts the type of resources that may be the value of a specific property range

17. Inferences from Constraints alice betty charles doris eve

18. Inferences from Constraints

19. Class Hierarchy rdfs:Class –Resources denoting a set of resources; range of rdf:type rdfs:subClassOf –Create class hierarchy rdf:type rdfs:class rdfs:subClassOf rdf:type rdf:class rdf:type rdf:class

20. Sub-Class Inferencing

21. Sub-class Inferencing Example

22. Jena Toolkit Robust tools for building and manipulating RDF models –HP Labs Bristol –Capabilities Model construction XML and N3 parsing Model persistence (DB foundation) Model querying Ontology building Inferencing http://www.hpl.hp.com/semweb/jena2.htm

23. IsaViz Visualizing and constructing RDF models http://www.w3.org/2001/11/IsaViz/