问题
I have written a custom builtin to use in my Project but I do not really know how I can use it.
I have written two classes. In one of them there is the builtin I have made (using BaseBuiltin
) and in the other one I have registered the new builtin (using BuiltinRegistry
).
I have already tried to use default builtins, writing rules that use them in a text file readable from Eclipse using Java. In this case I do not have any problems. How can I use the builtin I have built? Should I import (or include) something in some files?
回答1:
First you define a Builtin
, usually by extending BaseBuiltin
, and then you use BuiltinRegistry.theRegistry.register(Builtin)
to make it available to Jena rule-based inference.
Once you've done that, you need to actually use a rule that will reference your Builtin
in order to trigger it.
BuiltinRegistry.theRegistry.register( new BaseBuiltin() {
@Override
public String getName() {
return "example";
}
@Override
public void headAction( final Node[] args, final int length, final RuleContext context ) {
System.out.println("Head Action: "+Arrays.toString(args));
}
} );
final String exampleRuleString =
"[mat1: (?s ?p ?o)\n\t-> print(?s ?p ?o),\n\t example(?s ?p ?o)\n]"+
"";
System.out.println(exampleRuleString);
/* I tend to use a fairly verbose syntax for parsing out my rules when I construct them
* from a string. You can read them from whatever other sources.
*/
final List<Rule> rules;
try( final BufferedReader src = new BufferedReader(new InputStreamReader(new ByteArrayInputStream(exampleRuleString.getBytes()))) ) {
rules = Rule.parseRules(Rule.rulesParserFromReader(src));
}
/* Construct a reasoner and associate the rules with it */
final GenericRuleReasoner reasoner = (GenericRuleReasoner) GenericRuleReasonerFactory.theInstance().create(null);
reasoner.setRules(rules);
/* Create & Prepare the InfModel. If you don't call prepare, then
* rule firings and inference may be deferred until you query the
* model rather than happening at insertion. This can make you think
* that your Builtin is not working, when it is.
*/
final InfModel infModel = ModelFactory.createInfModel(reasoner, ModelFactory.createDefaultModel());
infModel.prepare();
/* Add a triple to the graph:
* [] rdf:type rdfs:Class
*/
infModel.createResource(RDFS.Class);
The output of this code will be:
- The string of the forward-chaining rule
- The result of calling the print
Builtin
- The result of calling the example
Builtin
... which is exactly what we see:
[mat1: (?s ?p ?o)
-> print(?s ?p ?o),
example(?s ?p ?o)
]
-2b47400d:14593fc1564:-7fff rdf:type rdfs:Class
Head Action: [-2b47400d:14593fc1564:-7fff, http://www.w3.org/1999/02/22-rdf-syntax-ns#type, http://www.w3.org/2000/01/rdf-schema#Class]
来源:https://stackoverflow.com/questions/23268298/once-ive-written-a-builtin-what-do-i-need-to-do-to-make-the-reasoners-aware-of