Presentation on theme: "Introduction to RDF Based on tutorial at www.w3schools.com."— Presentation transcript:
Introduction to RDF Based on tutorial at www.w3schools.com
Resource Description Framework A framework (not a language) for describing resources Model for data Syntax to allow exchange and use of information stored in various locations The point is to facilitate reading and correct use of information by computers, not necessarily by people
w3c recommendation Find the official recommendation at http://www.w3.org/RDF/s http://www.w3.org/RDF/s Note the subtle difference between a standard and a recommendation –w3c has no power to enforce compliance. –Obeying the rules in the recommendation allows a site to participate in the world wide web cooperative enterprise.
Identification and description RDF identifies resources with URIs –Often, though not always, the same as a URL –Anything that can have a URI is a RESOURCE RDF describes resources with properties and property values –A property is a resource that has a name Ex. Author, Book, Address, Client, Product –A property value is the value of the Property Ex. “Joanna Santillo,” http://www.someplace.com/, etc. A property value can be another resource, allowing nested descriptions.
Statements Resource, Property, Property Value Aka subject, predicate, object of a statement Predicates are not the same as English language verbs. –Specify a relationship between the subject and the object
Examples Statement: "The author of http://www.w3schools.com/RDF is Jan Egil Refsnes". Subject: http://www.w3schools.com/RDF Predicate: author Object: Jan Egil Refsnes Statement: "The homepage of http://www.w3schools.com/RDF is http://www.w3schools.com". Subject: http://www.w3schools.com/RDF Predicate: homepage Object: http://www.w3schools.com
Binary predicates RDF offers only binary predicates. Think of them as P(x,y) where P is the relationship between the objects x and y. From the example, X = http://www.w3schools.com/RDF Y = Jan Egil Refsnes P = author http://www.w3schools.com/RDF Jan Egil Refsnes author
Bob Dylan USA Columbia 10.90 1985 Bonnie Tyler UK CBS Records 9.90 1988 …. Root element of RDF documents Source of namespace for elements with rdf prefix Source of namespace for elements with cd prefix Description element describes the resource identified by the rdf:about attribute. Cd:country etc are properties of the resource.
RDF validator Check the correctness of an RDF document: http://www.w3.org/RDF/Validator/ Result shows the subject, predicate and object of each element of the document and a graph of the model.
Containers Groups of things: unordered list; duplicates allowed ordered list; duplicates allowed list of alternatives; one will be selected
Example <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:cd="http://www.recshop.fake/cd#"> <rdf:Description rdf:about="http://www.recshop.fake/cd/Beatles"> CD Record Tape Exactly one of these formats
Limiting the scope Collection - describes a group that contains only the specified members, no others. <rdf:Description rdf:about="http://recshop.fake/cd/Beatles">
RDF Schema Extension to RDF to allow definition of application-specific classes and properties –Does not define the classes, properties. –Provides a framework to describe such –Classes - similar to OOP Allows instances and subclasses of classes.
<rdf:RDF xmlns:rdf= "http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#" xml:base= "http://www.animals.fake/animals#"> <rdf:type rdf:resource="http://www.w3.org/2000/01/rdf-schema#Class"/> <rdf:type rdf:resource="http://www.w3.org/2000/01/rdf-schema#Class"/> Horse defined as subclass of animal
<rdf:RDF xmlns:rdf= "http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#" xml:base= "http://www.animals.fake/animals#"> Abbreviated version. Works because an RDFS class is an RDF resource. Use rdfs:Class instead of rdfDescription and drop the rdf:type information
Dublin Core RDF is metadata -- data about data Dublin core is a set of properties for describing documents See www.dublincore.org for detailswww.dublincore.org 15 basic elements: Contributor, coverage, creator, format, date, description, identifier, language, publisher, relation, rights, source, subject, title, type