org.aksw.jenax.sparql.fragment.api.Fragment2 Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of jenax-arq-relations Show documentation
There is a newer version: 5.0.0-1
package org.aksw.jenax.sparql.fragment.api;

import java.util.Arrays;
import java.util.Collections;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;

import org.aksw.jenax.sparql.fragment.impl.Concept;
import org.aksw.jenax.sparql.fragment.impl.Fragment2Impl;
import org.apache.jena.graph.Triple;
import org.apache.jena.sparql.core.BasicPattern;
import org.apache.jena.sparql.core.PathBlock;
import org.apache.jena.sparql.core.TriplePath;
import org.apache.jena.sparql.core.Var;
import org.apache.jena.sparql.graph.NodeTransform;
import org.apache.jena.sparql.syntax.Element;
import org.apache.jena.sparql.syntax.ElementGroup;
import org.apache.jena.sparql.syntax.ElementPathBlock;
import org.apache.jena.sparql.syntax.ElementTriplesBlock;

import com.google.common.collect.Sets;

public interface Fragment2
    extends GeneralizedFragment2
{
    Var getSourceVar();
    Var getTargetVar();

    @Override
    default Set getSourceVars() {
        return Collections.singleton(getSourceVar());
    }

    @Override
    default Set getTargetVars() {
        return Collections.singleton(getTargetVar());
    }

    default Set getMarkedVars() {
        Set result = new LinkedHashSet<>(Arrays.asList(getSourceVar(), getTargetVar()));
        return result;
    }

    default Set getIntermediaryVars() {
        Set mentionedVars = getVarsMentioned();
        Set markedVars = getMarkedVars();
        Set result = Sets.difference(mentionedVars, markedVars);

        return result;
    }

    default Fragment2 reverse() {
        Fragment2 result = new Fragment2Impl(getElement(), getTargetVar(), getSourceVar());
        return result;
    }

    /**
     * An empty relation does is equivalent to a zero-length path, i.e.
     * it navigates from a set of resources to the same set of resources.
     *
     * It is expressed as an empty graph pattern (ElementGroup), and
     * equal variables in source and target;
     *
     * @return
     */
    default boolean isEmpty() {
        boolean result;

        Element e = getElement();
        if(e instanceof ElementGroup) {
            ElementGroup g = (ElementGroup)e;
            result = g.getElements().isEmpty();

            //relation.getSourceVar().equals(relation.getTargetVar())
        } else {
            result = false;
        }

        return result;
    }


    default Concept getSourceConcept() {
        Concept result = new Concept(getElement(), getSourceVar());
        return result;
    }

    default Concept getTargetConcept() {
        Concept result = new Concept(getElement(), getTargetVar());
        return result;
    }

    default Fragment2 applyNodeTransform(NodeTransform nodeTransform) {
        Fragment2 result = Fragment.applyDefaultNodeTransform(this, nodeTransform).toFragment2();
        return result;
    }


    /** Upgrades triples to triple paths. */
    default TriplePath getAsTripleOrTriplePath() {
        Triple t = getAsTriple();
        TriplePath result = t != null
                ? new TriplePath(t)
                : getAsTriplePath();
        return result;
    }

    /**
     * If the relation is backed by a single ElementPathBlock with only a single TriplePath
     * then return it - otherwise return null.
     *
     */
    default TriplePath getAsTriplePath() {
        TriplePath result = null;
        Element elt = getElement();
        if (elt instanceof ElementPathBlock) {
            ElementPathBlock epb = (ElementPathBlock)elt;
            PathBlock pb = epb.getPattern();
            List tps = pb.getList();
            if (tps.size() == 1) {
                result = tps.get(0);
            }
        }
        return result;
    }

    default Triple getAsTriple() {
        Triple result = null;
        Element elt = getElement();
        if (elt instanceof ElementTriplesBlock) {
            ElementTriplesBlock block = (ElementTriplesBlock)elt;
            BasicPattern bp = block.getPattern();
            List tps = bp.getList();
            if (tps.size() == 1) {
                result = tps.get(0);
            }
        }
        return result;
    }

}