Resource description framework
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The document discusses Resource Description Framework (RDF), a W3C standard for describing web resources. RDF uses a graph-based data model consisting of subjects, predicates, and objects, known as triples. It provides a common framework for describing resources, along with their properties and relationships. RDF Schema builds upon RDF by defining additional vocabulary terms like class, subClassOf, and domain to organize RDF vocabularies and semantically relate terms. While useful, RDF Schema has limitations, leading to the development of OWL as a more expressive ontology language.
Resource description framework
- 1. Resource Description Framework STANLEY WANG SOLUTION ARCHITECT, TECH LEAD @SWANG68 http://www.linkedin.com/in/stanley-wang-a2b143b
- 2. • RDF is a W3C standard, which provides tool to describe Web resources provides interoperability between applications that exchange machine- understandable information • Composed of three basic elements Resources – the things being described Properties – the relationships between things Classes – the buckets used to group the things Resource Description Framework The elements are combined to make simple statements in the form of Triples: <Subject> <Predicate> <Object> Men In Black stars Will Smith <MenInBlack> <hasStar> <WillSmith>
- 3. Mary Director Secretary to_be_in_ love_with has_job has_job John has_homepage has_homepage Ontology RDF – Describe Semantic Web Resources
- 4. • Subject of an RDF statement is a resource • Predicate of an RDF statement is a property of a resource • Object of an RDF statement is the value of a property of a resource RDF Statement RDF Properties: type, subClassOf, subPropertyOf, range , domain, label,comment Subject (resource) http://www.w3.org/Home/Lassila Predicate (property) Creator Object (literal) “Ora Lassila” Ora Lassila is the creator of the resource http://www.w3.org/Home/Lassila.
- 5. RDF Example Ora Lassila is the creator of the resource http://www.w3.org/Home/Lassila. <rdf:RDF> <rdf:Description about= "http://www.w3.org/Home/Lassila"> <s:Creator>Ora Lassila</s:Creator> </rdf:Description> </rdf:RDF> Predicate
- 6. RDF for Semantic Annotation • RDF provides metadata about Web resources • Object -> Attribute-> Value triples • It has an XML syntax • Chained triples form a Graph http://sepang.nottingham.edu.my/~bpayam/images/payam-barnaghi.png has_image #Payam payam@nottingh am has_emailUNiM has_teaching http://www.nottingham.edu.my/CSIT/G53ELC has_owner <rdf:Description rdf:about=“#Payam”> <has_email>payam@nottingham</has_email> </rdf:Description> http://sepang.nottingham.edu.my/~bpayam/#Payam
- 7. RDF Schema • RDF Schema augments RDF to allow you to define vocabulary terms and the relations between those terms; • “extra meaning” to particular RDF predicates and resources e.g., Class, subClassOf, Property, domain, range • These terms are the RDF Schema building blocks (constructors) used to create vocabularies; • RDF semantically extends RDF by providing a means to describe RDF Vocabularies; RDF Schema is a W3C standard which defines vocabulary for RDF organizes this vocabulary in a typed hierarchy capable to explicitly declare semantic relations between vocabulary terms
- 8. What does RDF Schema add? • Defines vocabulary for RDF • Organizes this vocabulary in a typed hierarchy • class, subClassOf, type • property, subPropertyOf • domain, range AlanTom Staff Lecturer Research Assistant subClassOf subClassOf type supervisedBy domain range type supervisedBy Schema(RDFS) Data(RDF)
- 9. Limitation of RDF • RDF Schema is a vocabulary description language for describing properties and classes of RDF resources, with a semantics for generalization hierarchies of such properties and classes. • RDFS is useful, but does not solve all possible requirements. • Complex applications may want more possibilities: o similarity and/or differences of terms such as properties or classes o construct classes, not just name them o can a program reason about some terms? e.g. “if «Person» resources «A» and «B» have the same «foaf:email» property, then «A» and «B» are identical” This lead to the development of OWL (Web Ontology Language)