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Resource Description Framework (RDF)

Resource Description Framework (RDF). Lecture # 7 Faculty of Computer Science, IBA. RDF Schema. No assumption about particular domain nor defines the semantics of any domain. RDF Schema do so by vocabularies Classes, Properties. RDF Schema. Defines small vocabulary for RDF:

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Resource Description Framework (RDF)

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  1. Resource Description Framework (RDF) Lecture # 7 Faculty of Computer Science, IBA

  2. RDF Schema • No assumption about particular domain nor defines the semantics of any domain. • RDF Schema do so by vocabularies Classes, Properties. Quratulain

  3. RDF Schema • Defines small vocabulary for RDF: • Class, subClassOf, type • Property, subPropertyOf • domain, range Person subClassOf subClassOf range domain Student Researcher hasSuperVisor type type Frank Jeen hasSuperVisor Quratulain

  4. Basic Ideas of RDF Schema • RDF is a universal language that lets users describe resources in their own vocabularies • RDF does not assume, nor does it define semantics of any particular application domain • The user can do so in RDF Schema using: • Classes and Properties • Class Hierarchies and Inheritance • Property Hierarchies A Semantic Web Primer

  5. Classes and their Instances • We must distinguish between • Concrete “things” (individual objects) in the domain: Discrete Maths, David Billington etc. • Sets of individuals sharing properties called classes: lecturers, students, courses etc. • Individual objects that belong to a class are referred to as instances of that class • The relationship between instances and classes in RDF is through rdf:type A Semantic Web Primer

  6. Why Classes are Useful • Impose restrictions on what can be stated in an RDF document using the schema • As in programming languages • E.g. A+1, where A is an array • Disallow nonsense from being stated A Semantic Web Primer

  7. Nonsensical Statements disallowed through the Use of Classes • Discrete Maths is taught by Concrete Maths • We want courses to be taught by lecturers only • Restriction on values of the property “is taught by” (range restriction) • Room MZH5760 is taught by David Billington • Only courses can be taught • This imposes a restriction on the objects to which the property can be applied (domainrestriction) A Semantic Web Primer

  8. Class Hierarchies • Classes can be organized in hierarchies • A is a subclass of B if every instance of A is also an instance of B • Then B is a superclass of A • A subclass graph need not be a tree • A class may have multiple superclasses A Semantic Web Primer

  9. Class Hierarchy Example A Semantic Web Primer

  10. Inheritance in Class Hierarchies • Range restriction: Courses must be taught by academic staff members only • Michael Maher is a professor • He inheritsthe ability to teach from the class of academic staff members • This is done in RDF Schema by fixing the semantics of “is a subclass of” • It is not up to an application (RDF processing software) to interpret “is a subclass of A Semantic Web Primer

  11. Property Hierarchies • Hierarchical relationships for properties • E.g., “is taught by” is a subproperty of “involves” • If a course C is taught by an academic staff member A, then C also involves Α • The converse is not necessarily true • E.g., A may be the teacher of the course C, or • a tutor who marks student homework but does not teach C • P is a subproperty of Q, if Q(x,y) is true whenever P(x,y) is true A Semantic Web Primer

  12. RDF Layer vs RDF Schema Layer • Discrete Mathematics is taught by David Billington • The schema is itself written in a formal language, RDF Schema, that can express its ingredients: • subClassOf, Class, Property, subPropertyOf, Resource, etc. A Semantic Web Primer

  13. RDF Layer vs RDF Schema Layer (2) A Semantic Web Primer

  14. Quratulain

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