SPARQL

SPARQL is a W3C standard. It is a query language for RDF (SPARQL: SPARQL Protocol And RDF Query Language). Please note that OntoBroker only implements a subset of SPARQL (and SPARQL only supports a subset of the ObjectLogic query features). The following table shows how we interpret SPARQL queries in OntoBroker for ObjectLogic ontologies:

Subject	Predicate	Object	ObjectLogic	Comment
?S	rdf:type	rdfs:Class	_concepts(?S)	All classes
?S	rdf:type	rdf:Property	_properties(?S)	All properties (i.e. attributes and relations)
?S	rdf:type	?O	?S:?O AND ...	Instances (including instances of meta-classes rdfs:Class and rdf:Property)
?S	rdfs:subClassOf	?O	?S::?O	Sub-classes
?S	rdfs:subPropertyOf	?O	?S<<?O	Sub-properties
?S	rdfs:range	?O	_PropertyRange(?S,?O)	RDFS domain (not part of OL)
?S	rdfs:domain	?O	_PropertyDomain(?S,?O)	RDFS range (not part of OL)

Some examples are given below. The first example is a simple query with two triples in the WHERE part of the SPARQL query.

SELECT *
WHERE {
?CAR a <http://example.com/#car> ;
<http://example.com/#price> ?PRICE
}

This SPARQL query could also be expressed using the ObjectLogic query

?- ?CAR:<http://example.com/#car> AND ?CAR[<http://example.com/#price>->?PRICE].

This example shows a query for subclass relationships. When we have the ObjectLogic ontology:

Developer::Employee.

ProjectManager::Employee.

Then the following query

SELECT ?X

WHERE {

?X rdfs:subClassOf ?Y

}

will return:

--------------

Developer

ProjectManager

This SPARQL query could also be expressed with the ObjectLogic query

@{options[outorder(?X)]} ?- ?X::?Y.