2. RDF Semantic Web Basics Semantic Web

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1 2. RDF Semantic Web Basics Semantic Web Prof. Dr. Bernhard Humm Faculty of Computer Science Hochschule Darmstadt University of Applied Sciences Summer semester

2 Agenda Semantic Web Basics Literature 2

3 Resources, URIs and namespaces Resource: anything that someone might want to talk about, e.g. - Shakespeare - All cows in Texas - The value of x RDF: Resource Description Framework Every resource is has Uniform Resource Identifier (URI), e.g. Abbreviation scheme: qnames with lit: < lit:shakespeare 3

4 Standard Namespaces rdf: Description Resource Description Framework URI Namespace rdfs: RDF Schema owl: Web Ontology Language xsd: XML Schema 4

5 Triples the basic statement notation of Semantic Web Languages Statement including subject, predicate, and object Subject: resource Predicate: resource Object: resource or value (XML data type) Example: lit:shakespeare lit:wrote lit:king_lear. 5

6 Classes and Instances: rdf:type and rdfs:class rdf:type expresses instance relationship rdfs:class represents a meta-class Examples: lit:shakespeare rdf:type lit:playwright. lit:playwright rdf:type rdfs:class. Abbreviation for rdf:type : a lit:shakespeare a lit:playwright. lit:playwright a rdfs:class. 6

7 Classes / Instances in Semantic Web vs. Object-Orientation Concept of class (group) and instances (individuals) in Semantic Web comparable with Object-Orientation But there are major differences: Object-Orientation No instance without class Instance belongs to exactly one class Class specifies attributes and methods of all instances Semantic Web Any resource can be used no need for specifying a class and a rdf:type relationship Zero, one, or many rdf:type relationships may be specified No restrictions on the relationships of instances whatsoever. Methods have no equivalent at all 7

8 Properties: rdf:property, rdfs:domain, rdfs:range rdf:property class for predicates rdfs:domain subject type rdfs:range object type Example: 8

9 Properties in Semantic Web vs. Object-Orientation Properties comparable with associations between class instances But there are major differences: Object-Orientation Associations between instances are specified in class definition Types of association ends are specified Type violations result in errors (compile time or run-time) Semantic Web No need for specifying rdf:type rdf:property No need for specifying rdf:domain No need for specifying rdf:range No type checking (neither compile time nor run-time) Instead: Reasoning results may be not as expected 9

10 Complete Example 10

11 Agenda Semantic Web Basics Literature 11

12 Literature Dean Allemang, James Hendler: Semantic Web for the Working Ontologist: Effective Modeling in RDFS and OWL. Morgan Kaufmann Publishers Inc., San Francisco, CA, USA, Read Chapter 3: RDF The Basis of the Semantic Web 12

2. Knowledge Representation Applied Artificial Intelligence

2. Knowledge Representation Applied Artificial Intelligence Prof. Dr. Bernhard Humm Faculty of Computer Science Hochschule Darmstadt University of Applied Sciences 1 Retrospective Introduction to AI What