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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

Resource Description Framework (RDF)

Lecture # 7

Faculty of Computer Science, IBA


Rdf schema
RDF Schema

  • No assumption about particular domain nor defines the semantics of any domain.

  • RDF Schema do so by vocabularies Classes, Properties.

Quratulain


Rdf schema1
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


Basic ideas of rdf schema
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


Classes and their instances
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


Why classes are useful
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


Nonsensical statements disallowed through the use of classes
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


Class hierarchies
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


Class hierarchy example
Class Hierarchy Example

A Semantic Web Primer


Inheritance in class hierarchies
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


Property hierarchies
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


Rdf layer vs rdf schema layer
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


Rdf layer vs rdf schema layer 2
RDF Layer vs RDF Schema Layer (2)

A Semantic Web Primer



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