Jena API Rules Test : how many and what are the methods to write rules in Jena?

Question

I succeeded in creating, modifying, merging ontologies with Jena API and Eclipse. I succeeded also in starting the OWL reasoner and Pellet reasoner in Eclipse.

Now I would like to understand how can I write a simple rule in Eclipse using Jena API and if there is one or more methods for doing this.

For example, in Protégé I used to write a rule in SWRL like this, to calculate the mean of a triangular distribution:

TriangularDistribution(?t), hasLowerLimit(?t,?a), hasUpperLimit(?t,?c), hasMode(?t,?b), add(?ab, ?a, ?b), add(?abc, ?ab, ?c), divide(?m, ?abc, 3) -> hasMean(?t, ?m)

How can I translate it using Jena?

======== UPGRADE =========

In order to better understand how can I create rules in Jena, I followed the example in https://jena.apache.org/documentation/inference/#RULEexamples

I created three files: The first is "ReasoningJena.java"

    package test01;

import com.hp.hpl.jena.rdf.model.*;
import com.hp.hpl.jena.reasoner.*;
import com.hp.hpl.jena.reasoner.rulesys.*;
import com.hp.hpl.jena.vocabulary.ReasonerVocabulary;
import com.hp.hpl.jena.util.*;
import java.io.*;

public class ReasoningJena {
    private static Model reason(Model input) {

        // Register a namespace to be used in the rules
        String flUri = "http://www.snee.com/ns/demo#";
        PrintUtil.registerPrefix("fl", flUri);

        // Create an (RDF) specification of a hybrid reasoner which loads its rules from an external file.
        Model m = ModelFactory.createDefaultModel();
        Resource configuration =  m.createResource();
        configuration.addProperty(ReasonerVocabulary.PROPruleMode, "hybrid");
        configuration.addProperty(ReasonerVocabulary.PROPruleSet,  "C:/Users/pecore/Desktop/file.rules");

        // Create an instance of such a reasoner
        Reasoner reasoner = GenericRuleReasonerFactory.theInstance().create(configuration);

        // Infere new knowledge on the input model, generating a new one
        InfModel infmodel = ModelFactory.createInfModel(reasoner, input);

        return infmodel;
        }


        private static Model readModelFromFile(String filePath) throws Exception {

        // Create an empty model
        Model model = ModelFactory.createDefaultModel();

        // Use the FileManager to find the input file
        InputStream in = new FileInputStream(new File(filePath));

        // Read the RDF/XML file
        model.read(in, "");

        return model;
        }

        public static void main(String[] args){
            try {



                Model model = readModelFromFile("C:/Users/pecore/Desktop/demoData.rdf");
                System.out.println("The model has " + model.size() + " statements");
                // Do the reasoning
                model = reason(model);
                System.out.println("After inferencing the model has " + model.size() + " statements");


            }
            catch(Exception e) {
                e.printStackTrace();
            }  
        }
     }

The rdf file is : "demoData.rdf"

  <?xml version="1.0"?>

<!DOCTYPE rdf:RDF [
    <!ENTITY rdf  'http://www.w3.org/1999/02/22-rdf-syntax-ns#'>
    <!ENTITY rdfs 'http://www.w3.org/2000/01/rdf-schema#'>
    <!ENTITY demo 'http://jena.hpl.hp.com/demo#'>
]>

<rdf:RDF xmlns:rdf="&rdf;" 
         xmlns:rdfs="&rdfs;" 
         xmlns:demo="&demo;"
         xmlns="&demo;"
         >

    <demo:TransProp rdf:about="&demo;p" />

    <rdf:Description rdf:about="&demo;a">
        <p rdf:resource="&demo;b" />
    </rdf:Description>

    <rdf:Description rdf:about="&demo;c">
        <p rdf:resource="&demo;a" />
    </rdf:Description>

    <rdf:Description rdf:about="&demo;b">
        <p rdf:resource="&demo;d" />
    </rdf:Description>

</rdf:RDF>

And the rules file is : "file.rules"

@prefix = "http://www.snee.com/ns/demo#";
[transitiveRule: (?A demo:p ?B), (?B demo:p ?C) -> (?A > demo:p ?C) ];

I run all in Eclipse SW Version: Luna Service Release 2 (4.4.2) with JDK 1.7 And I obtained these errors:

 log4j:WARN No appenders could be found for logger (org.apache.jena.riot.system.stream.JenaIOEnvironment).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
The model has 4 statements
com.hp.hpl.jena.shared.PrefixMapping$IllegalPrefixException: =

    at com.hp.hpl.jena.shared.impl.PrefixMappingImpl.checkLegal(PrefixMappingImpl.java:157)
    at com.hp.hpl.jena.shared.impl.PrefixMappingImpl.setNsPrefix(PrefixMappingImpl.java:67)
    at com.hp.hpl.jena.shared.impl.PrefixMappingImpl.setNsPrefixes(PrefixMappingImpl.java:147)
    at com.hp.hpl.jena.reasoner.rulesys.Rule$Parser.registerPrefixMap(Rule.java:716)
    at com.hp.hpl.jena.reasoner.rulesys.Rule.rulesParserFromReader(Rule.java:567)
    at com.hp.hpl.jena.reasoner.rulesys.Util.loadRuleParserFromResourceFile(Util.java:264)
    at com.hp.hpl.jena.reasoner.rulesys.FBRuleReasoner.loadRules(FBRuleReasoner.java:270)
    at com.hp.hpl.jena.reasoner.rulesys.GenericRuleReasoner.doSetParameter(GenericRuleReasoner.java:301)
    at com.hp.hpl.jena.reasoner.rulesys.FBRuleReasoner.doSetRDFNodeParameter(FBRuleReasoner.java:370)
    at com.hp.hpl.jena.reasoner.rulesys.FBRuleReasoner.loadConfiguration(FBRuleReasoner.java:101)
    at com.hp.hpl.jena.reasoner.rulesys.GenericRuleReasoner.<init>(GenericRuleReasoner.java:96)
    at com.hp.hpl.jena.reasoner.rulesys.GenericRuleReasonerFactory.create(GenericRuleReasonerFactory.java:56)
    at test01.ReasoningJena.reason(ReasoningJena.java:24)
    at test01.ReasoningJena.main(ReasoningJena.java:55)

Why?

=========== UPDATE 2 ============ I made some changes on "file.rules" internal code correcting it as:

@prefix demo: <http://domain/demo#>.
[transitiveRule: (?A demo:p ?B), (?B demo:p ?C) -> (?A > demo:p ?C) ]

and I obtained this error code:

 log4j:WARN No appenders could be found for logger (org.apache.jena.riot.system.stream.JenaIOEnvironment).
    log4j:WARN Please initialize the log4j system properly.
    log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
    org.apache.jena.riot.RiotException: [line: 1, col: 8 ] The processing instruction target matching "[xX][mM][lL]" is not allowed.
        at org.apache.jena.riot.system.ErrorHandlerFactory$ErrorHandlerStd.fatal(ErrorHandlerFactory.java:136)
        at org.apache.jena.riot.lang.LangRDFXML$ErrorHandlerBridge.fatalError(LangRDFXML.java:253)
        at com.hp.hpl.jena.rdfxml.xmlinput.impl.ARPSaxErrorHandler.fatalError(ARPSaxErrorHandler.java:48)
        at com.hp.hpl.jena.rdfxml.xmlinput.impl.XMLHandler.warning(XMLHandler.java:200)
        at com.hp.hpl.jena.rdfxml.xmlinput.impl.XMLHandler.fatalError(XMLHandler.java:230)
        at org.apache.xerces.util.ErrorHandlerWrapper.fatalError(Unknown Source)
        at org.apache.xerces.impl.XMLErrorReporter.reportError(Unknown Source)
        at org.apache.xerces.impl.XMLErrorReporter.reportError(Unknown Source)
        at org.apache.xerces.impl.XMLErrorReporter.reportError(Unknown Source)
        at org.apache.xerces.impl.XMLScanner.reportFatalError(Unknown Source)
        at org.apache.xerces.impl.XMLScanner.scanPIData(Unknown Source)
        at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanPIData(Unknown Source)
        at org.apache.xerces.impl.XMLScanner.scanPI(Unknown Source)
        at org.apache.xerces.impl.XMLDocumentScannerImpl$PrologDispatcher.dispatch(Unknown Source)
        at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
        at org.apache.xerces.parsers.DTDConfiguration.parse(Unknown Source)
        at org.apache.xerces.parsers.DTDConfiguration.parse(Unknown Source)
        at org.apache.xerces.parsers.XMLParser.parse(Unknown Source)
        at org.apache.xerces.parsers.AbstractSAXParser.parse(Unknown Source)
        at com.hp.hpl.jena.rdfxml.xmlinput.impl.RDFXMLParser.parse(RDFXMLParser.java:151)
        at com.hp.hpl.jena.rdfxml.xmlinput.ARP.load(ARP.java:119)
        at org.apache.jena.riot.lang.LangRDFXML.parse(LangRDFXML.java:143)
        at org.apache.jena.riot.RDFParserRegistry$ReaderRIOTLang.read(RDFParserRegistry.java:185)
        at org.apache.jena.riot.RDFDataMgr.process(RDFDataMgr.java:906)
        at org.apache.jena.riot.RDFDataMgr.read(RDFDataMgr.java:257)
        at org.apache.jena.riot.RDFDataMgr.read(RDFDataMgr.java:243)
        at org.apache.jena.riot.adapters.RDFReaderRIOT_Web.read(RDFReaderRIOT_Web.java:62)
        at com.hp.hpl.jena.rdf.model.impl.ModelCom.read(ModelCom.java:247)
        at zero.readModelFromFile(zero.java:40)
        at zero.main(zero.java:50)

Your prefix syntax isn't right. The documentation shows an example: @prefix pre: <http://domain/url#>.. You have @prefix = "http://www.snee.com/ns/demo#";. There shouldn't be an = sign, you need to specify the prefix, you need to wrap the URI in angle brackets, and it should end with ., not ;. It's just a typo. And rules don't end with ;. — Joshua Taylor
Your question keeps changing. That's not particularly helpful. Anyhow, your new problem has to do with reading the model in, and nothing to do with Jena API Rules Test : how many and what are the methods to write rules in Jena?. You should ask a new question, except that this one is pretty clear: you've written too much code. Your whole readModelFromFile can be removed. Just do Model model = RDFDataMgr.loadModel("file://...");. — Joshua Taylor

Joshua Taylor Joshua Taylor · Accepted Answer · 2015-05-26T13:13:30

There are a few different questions here. There are lots of examples on Stack Overflow and elsewhere of how to write Jena rules, so I think the key question here is how to rewrite this specific SWRL rule. Without your showing any attempts, we don't know what problems you were running into, but I think that a SWRL rule like:

TriangularDistribution(?t), hasLowerLimit(?t,?a), hasUpperLimit(?t,?c), hasMode(?t,?b), add(?ab, ?a, ?b), add(?abc, ?ab, ?c), divide(?m, ?abc, 3) &rightarrow; hasMean(?t, ?m)

would simply become something like this:

@prefix : <...>

[(?x rdf:type TriangularDistribution)
 (?t :hasLowerLimit ?a)
 (?t :hasUpperLimit ?c)
 (?t :hasMode ?b)
 sum(?a, ?b, ?ab)
 add(?ab, ?c, ?abc)
 quotient(?abc, 3, ?m)
 ->
 (?t :hasMean ?m)]

I didn't remember the math builtins in Jena, so I looked at the list of builtin primitives.

Jena API Rules Test : how many and what are the methods to write rules in Jena?

1 Answers