Statements in XML (3) e An rdf document is represented by an XMl element with the tag rdf: RDF The content of this element is a number of descriptions, which use rdf: Description tags Every description makes a statement about a resource, identified in 3 ways an about attribute, referencing an existing resource an ID attribute, creating a new resource without a name, creating an anonymous resource 16 Chapter 3 A Semantic Web primer
Chapter 3 A Semantic Web Primer 16 Statements in XML (3) ⚫ An RDF document is represented by an XML element with the tag rdf:RDF ⚫ The content of this element is a number of descriptions, which use rdf:Description tags. ⚫ Every description makes a statement about a resource, identified in 3 ways: – an about attribute, referencing an existing resource – an ID attribute, creating a new resource – without a name, creating an anonymous resource
Statements in XML (4) The rdf: Description element makes a statement about the resource http://www.citgu.edu.aul-db o Within the description ne property is used as a tag the content is the value of the property 17 Chapter 3 A Semantic Web primer
Chapter 3 A Semantic Web Primer 17 Statements in XML (4) ⚫ The rdf:Description element makes a statement about the resource http://www.cit.gu.edu.au/~db ⚫ Within the description – the property is used as a tag – the content is the value of the property
Reification o In RDf it is possible to make statements about statements Grigoris believes that David Billington is the creatorofhttp://www.cit.gu.edu.au/-db e Such statements can be used to describe belief or trust in other statements o The solution is to assign a unique identifier to each statement It can be used to refer to the statement 18 Chapter 3 A Semantic Web primer
Chapter 3 A Semantic Web Primer 18 Reification ⚫ In RDF it is possible to make statements about statements – Grigoris believes that David Billington is the creator of http://www.cit.gu.edu.au/~db ⚫ Such statements can be used to describe belief or trust in other statements ⚫ The solution is to assign a unique identifier to each statement – It can be used to refer to the statement
Reification(2) o Introduce an auxiliary object(e.g. belief) o relate it to each of the 3 parts of the original statement through the properties subject, predicate and object o In the preceding example subject of belief is David Billington predicate of belief is creator objectofbeliefishttp://www.cit.gu.eduau/-db 19 Chapter 3 A Semantic Web primer
Chapter 3 A Semantic Web Primer 19 Reification (2) ⚫ Introduce an auxiliary object (e.g. belief1) ⚫ relate it to each of the 3 parts of the original statement through the properties subject, predicate and object ⚫ In the preceding example – subject of belief1 is David Billington – predicate of belief1 is creator – object of belief1 is http://www.cit.gu.edu.au/~db
Data Types o Data types are used in programming languages to allow interpretation o In RdF, typed literals are used, if necessary (“ David Billington”, http://www.mydomain.orglage, 27aahttp://www.w3.org/2001/xmlschen integer) 20 Chapter 3 A Semantic Web primer
Chapter 3 A Semantic Web Primer 20 Data Types ⚫ Data types are used in programming languages to allow interpretation ⚫ In RDF, typed literals are used, if necessary (“David Billington”, http://www.mydomain.org/age, “27”^^http://www.w3.org/2001/XMLSchem a#integer)