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SPARQL-MM is a multimedia-extension for SPARQL 1.1 (www.w3.org/TR/sparql11-query/‎) implemented for Sesame (http://www.openrdf.org/).

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package com.github.tkurz.sparqlmm.function.temporal.relation;

import com.github.tkurz.media.ontology.exception.NotComparableException;
import com.github.tkurz.media.ontology.function.TemporalFunction;
import com.github.tkurz.media.ontology.type.TemporalEntity;
import com.github.tkurz.sparqlmm.Constants;
import com.github.tkurz.sparqlmm.doc.FunctionDoc;
import com.github.tkurz.sparqlmm.utils.FunctionHelper;
import org.openrdf.model.Value;
import org.openrdf.model.ValueFactory;
import org.openrdf.query.algebra.evaluation.ValueExprEvaluationException;
import org.openrdf.query.algebra.evaluation.function.Function;

/**
 * ...
 * 
 * Author: Thomas Kurz ([email protected])
 */
@FunctionDoc(title = "meets", properties = {TemporalEntity.class, TemporalEntity.class}, reference = FunctionDoc.Reference.temporal, description = "returns true if resource1.start = resource2.end or resource1.end = resource2.start, else false.")
public class MeetsFunction implements Function {
    /**
     * return the URI
     */
    public String getURI() {
        return Constants.NAMESPACE + "temporalMeets";
    }

    @Override
    public Value evaluate(ValueFactory valueFactory, Value... values) throws ValueExprEvaluationException {
        try {
            //check preconditions
            if(values.length != 2 || !FunctionHelper.isComparable(values)) return FunctionHelper.BOOL_LITERAL_FALSE;


            //check if values are correct
            TemporalEntity[] entities = FunctionHelper.toTemporalEntities(values);

            //evaluate
            return valueFactory.createLiteral(TemporalFunction.meets(entities[0], entities[1]));

        } catch (IllegalArgumentException | NotComparableException e) {
            return FunctionHelper.BOOL_LITERAL_FALSE;
        }
    }
}