OO jDREW - How to use The Complete OO jDREW API (COjDA)

How to use COjDA - Complete OO jDREW API

Creating a COjDA Object in Java

There are six different ways to create a COjDA object. For complete details about COjDA readers are refered to the JavaDoc for COjDA. One way to create a COjDA api object is to use a RDFS taxonomy and POSL knowledge base. For example you have a file called Types.rdfs that contains the following:

<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://example.org/schemas/vehicles">
 
    <rdf:Description rdf:ID="Vehicle">
      <rdf:type rdf:resource="http://www.w3.org/2000/01/rdf-schema#Class"/>
    </rdf:Description>
 
    <rdf:Description rdf:ID="PassengerVehicle">
      <rdf:type rdf:resource="http://www.w3.org/2000/01/rdf-schema#Class"/>
      <rdfs:subClassOf rdf:resource="#Vehicle"/>
    </rdf:Description>
 
    <rdf:Description rdf:ID="Van">
      <rdf:type rdf:resource="http://www.w3.org/2000/01/rdf-schema#Class"/>
      <rdfs:subClassOf rdf:resource="#Vehicle"/>
    </rdf:Description>
 
    <rdf:Description rdf:ID="Car">
      <rdf:type rdf:resource="http://www.w3.org/2000/01/rdf-schema#Class"/>
      <rdfs:subClassOf rdf:resource="#PassengerVehicle"/>
    </rdf:Description>
 
    <rdf:Description rdf:ID="MiniVan">
      <rdf:type rdf:resource="http://www.w3.org/2000/01/rdf-schema#Class"/>
      <rdfs:subClassOf rdf:resource="#Van"/>
      <rdfs:subClassOf rdf:resource="#PassengerVehicle"/>
    </rdf:Description>
 
    <rdf:Description rdf:ID="Sedan">
      <rdf:type rdf:resource="http://www.w3.org/2000/01/rdf-schema#Class"/>
      <rdfs:subClassOf rdf:resource="#Car"/>
    </rdf:Description>
 
    <rdf:Description rdf:ID="SportsCoupe">
      <rdf:type rdf:resource="http://www.w3.org/2000/01/rdf-schema#Class"/>
      <rdfs:subClassOf rdf:resource="#Car"/>
    </rdf:Description>
 
    <rdf:Description rdf:ID="ToyotaCorolla">
      <rdf:type rdf:resource="http://www.w3.org/2000/01/rdf-schema#Class"/>
      <rdfs:subClassOf rdf:resource="#Sedan"/>
    </rdf:Description>
 
</rdf:RDF>

Also you have a file called KB.posl that contains the following:

	discount(?customer, ?product, percent5) :- premium(?customer), regular(?product).
	base_price(customer->[sex->male!?]; vehicle->? : Car; price->650 : Integer).
	base_price(customer->[sex->male!?]; vehicle->? : Van; price->725 : Integer).

You can create a COjDA api object by using the following Code:

	  
	File types = new File("Types.rdfs");
	File kb = new File("KB.posl");
	COjDA api = new COjDA(COjDA.POSL, COjDA.RDFS, kb, types);

Once you have created the COjDA object you can then execute KB queries and Taxonomy queries. For a full list of a methods avaible to COjDA readers are refered to the JavaDoc of COjDA. An example KB query would be the following:

base_price(customer->[sex->male; name->"John Doe"; age->28]; vehicle->vehicle:ToyotaCorolla; price->?money:Integer). To execute this query using COjDA the following code would be used:

	  
	String kbPOSLQuery = "base_price(customer->[sex->male; name->\"John Doe\"; age->28]; vehicle->vehicle:ToyotaCorolla; price->?money:Integer).";
	String result = api.issueKBQuery_POSL(kbPOSLQuery);

The resulting RuleML answer expression would look as follows:


<RuleML>
	<Answer>
		<Rulebase>
			<Equal>
				<Var type="Integer">money</Var>
				<Ind type="Integer">650</Ind>
			</Equal>
		</Rulebase>
	</Answer>
</RuleML>

To execute a Taxonomy Query the following code could be used:

	  
	String taxonomyPOSLQuery = "subsumesPlus(?X, MiniVan)";
	String resultTaxonomy = api.issueTaxonomyQuery_POSL(taxonomyPOSLQuery);

The resulting RuleML answer expression would look as follows:


<RuleML>
	<Answer>
		<Rulebase>
			<Equal>
				<Var>X</Var>
				<Ind>Van</Ind>
			</Equal>
		</Rulebase>
		<Rulebase>
			<Equal>
				<Var>X</Var>
				<Ind>PassengerVehicle</Ind>
			</Equal>
		</Rulebase>
		<Rulebase>
			<Equal>
				<Var>X</Var>
				<Ind>Vehicle</Ind>
			</Equal>
		</Rulebase>
	</Answer>
</RuleML>

For more information about RuleML answer expressions and how to query the taxonomy, readers are referred to the documents of Taxonomy Querying and the Taxonomy Querying API.

Last Updated:
July 30, 2008

By:
Ben Craig