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Swoogle Manual


We describe the meaning of some of special terms as used in Swoogle. Some of these, such as class, may have have a well defined meaning in RDF or OWL. For these, we describe the process Swoogle in identifying instances. Other terms, such as ontology, tend to be informally defined or have several meanings depending on the context in which they are used. For these we give a definition appropriate for Swoogle.

Class

A class refers to a rdfs:Resource which is an instance of rdfs:Class. In Swoogle, given a triple (X,Y,Z), X is a reachable class if and only if the following constraints are met:


Individual

An individual refers to a rdfs:Resource which is an instance of owl:Thing or daml:Thing. In Swoogle, given a triple (X,Y,Z), X is a reachable individual if and only if the following constraints hold:

  • X is not anonymous

  • Y is rdf:type

  • Z is any of: owl:Thing,  daml:Thing or a class whose namespace is none of { owl, rdf, rdfs, daml}.


Ontology Ratio

The ontology ratio shows the proportion of defined classes and properties to all defined terms in a SWD.  Given a SWD foo,  its ontology ratio R(foo) is calculated by the following equation.

        R(foo) = ( |C(foo)| + |P(foo) |) / ( |C(foo) | + |P(foo) | +|I(foo) | )

where C(foo), P(foo), I(foo) refer to the sets of defined classes, defined properties and defined individuals in foo respectively.


Property

A property refers to a rdfs:Resource which is an instance of rdf:Property. In Swoogle, given a triple (X,Y,Z), X is a reachable property if and only if the following constraints are met:

  • X is not anonymous

  • Y is rdf:type

  • Z is any of Meta-properties -- rdf:Property, owl:ObjectProperty, owl:DatatypeProperty, owl:AnnotationProperty, owl:FunctionalProperty, owl:InverseFunctionalProperty, owl:SymmetricProperty, owl:OntologyProperty,owl:TransitiveProperty, daml:Property, daml:ObjectProperty, daml:DatatypeProperty, daml:TransitiveProperty, and daml:UniqueProperty.


Semantic Web Document (SWD)

Swoogle considers a Semantic Web document to be a document represented as an RDF graph. Currently there are three accepted syntactical encodings for RDF graph, namely 'RDF/XML', 'N-Triples' and 'N3'. Although not required, SWDs employing these grammars usually have suffices '.rdf', '.nt' and '.n3' respectively. Note that we do not consider a XHTML document with embedded RDF to be a SWD. This definition may be relaxed in the future as standards appear for embedding RDF in XHTML and as new encodings for RDF become popular.


Semantic Web Ontology (SWO)

A Semantic Web Ontology is a special type of SWD which defines many Classes and Properties. It consists of information that is stored in the T-box of a Description Logic system. In practice, a SWD is a SWO iff its Ontology Ratio is no less than 0.8.


Semantic Web Database (SWDB)

A Semantic Web Database is a special type of SWD which does not define Class or Property. It corresponds to forms that are stored in the A-box in a Description Logic system. In practice, a SWD is a SWDB iff its Ontology Ratio is 0.


Term

A term refers to a rdfs:Resource node in a SWD.

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