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* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.jena.sparql.path.eval ;
import java.util.ArrayList ;
import java.util.Collection ;
import java.util.Iterator ;
import java.util.List ;
import org.apache.jena.atlas.iterator.Iter ;
import org.apache.jena.graph.Graph ;
import org.apache.jena.graph.Node ;
import org.apache.jena.graph.Triple ;
import org.apache.jena.query.ARQ ;
import org.apache.jena.sparql.core.Var ;
import org.apache.jena.sparql.engine.ExecutionContext ;
import org.apache.jena.sparql.engine.QueryIterator ;
import org.apache.jena.sparql.engine.binding.Binding ;
import org.apache.jena.sparql.engine.binding.BindingFactory ;
import org.apache.jena.sparql.engine.iterator.QueryIterRoot ;
import org.apache.jena.sparql.path.P_NegPropSet ;
import org.apache.jena.sparql.path.Path ;
import org.apache.jena.sparql.path.eval.PathEvaluator.FilterExclude ;
import org.apache.jena.sparql.pfunction.* ;
import org.apache.jena.sparql.util.Context ;
import org.apache.jena.sparql.util.graph.GraphContainerUtils ;
import org.apache.jena.sparql.util.graph.GraphList ;
import org.apache.jena.sparql.vocabulary.ListPFunction ;
import org.apache.jena.vocabulary.RDFS ;
abstract public class PathEngine
{
private final boolean doingRDFSmember ;
private final boolean doingListMember ;
private final Graph graph ;
private final Context context ;
private final PropertyFunctionRegistry registry ;
protected PathEngine(Graph graph, Context context) {
boolean doingRDFSmember$ = false ;
boolean doingListMember$ = false ;
PropertyFunctionRegistry registry$ = null ;
if ( context == null || context.isTrueOrUndef(ARQ.propertyFunctions) ) {
registry$ = PropertyFunctionRegistry.chooseRegistry(context) ;
if ( registry$ != null ) {
doingRDFSmember$ = ( registry$.get(RDFSmember.getURI()) != null ) ;
doingListMember$ = ( registry$.get(ListMember.getURI()) != null ) ;
}
}
this.registry = registry$ ;
this.doingRDFSmember = doingRDFSmember$ ;
this.doingListMember = doingListMember$ ;
this.graph = graph ;
this.context = context ;
}
protected final Iter<Node> eval(Path path, Node node) {
return PathEval.eval$(graph, node, path, this) ;
}
protected final void eval(Path path, Node node, Collection<Node> output) {
PathEval.eval$(graph, node, path, this, output) ;
}
protected abstract void flipDirection() ;
protected abstract boolean direction() ;
// protected abstract void doOne(Path pathStep, Node node, Collection<Node> output) ;
// Because for SP? or ?PO, no duplicates occur, so works for both strategies.
protected final Iterator<Node> doOne(Node node, Node property) {
Iterator<Node> iter2 = null ;
if ( direction() ) {
Iter<Triple> iter1 = Iter.iter(graphFind(node, property, Node.ANY)) ;
iter2 = iter1.map(Triple::getObject) ;
} else {
Iter<Triple> iter1 = Iter.iter(graphFind(Node.ANY, property, node)) ;
iter2 = iter1.map(Triple::getSubject) ;
}
return iter2 ;
}
protected abstract void doSeq(Path pathStepLeft, Path pathStepRight, Node node, Collection<Node> output) ;
protected abstract void doAlt(Path pathStepLeft, Path pathStepRight, Node node, Collection<Node> output) ;
// path*
protected abstract void doZeroOrMore(Path pathStep, Node node, Collection<Node> output) ;
// path+
protected abstract void doOneOrMore(Path pathStep, Node node, Collection<Node> output) ;
// path?
protected abstract void doZeroOrOne(Path pathStep, Node node, Collection<Node> output) ;
protected abstract void doNegatedPropertySet(P_NegPropSet pathNotOneOf, Node node, Collection<Node> output) ;
// path{*} : possibly counting (if the engine supports that): default implementation
protected void doZeroOrMoreN(Path pathStep, Node node, Collection<Node> output) {
doZeroOrMore(pathStep, node, output) ;
}
// path{+} : possibly counting (if the engine supports that): default implementation
protected void doOneOrMoreN(Path pathStep, Node node, Collection<Node> output) {
doOneOrMore(pathStep, node, output) ;
}
protected abstract void doZero(Path path, Node node, Collection<Node> output) ;
// {N,M} and variations
protected abstract void doFixedLengthPath(Path pathStep, Node node, long fixedLength, Collection<Node> output) ;
protected abstract void doMultiLengthPath(Path pathStep, Node node, long min, long max, Collection<Node> output) ;
protected final void fill(Iterator<Node> iter, Collection<Node> output) {
for (; iter.hasNext();)
output.add(iter.next()) ;
}
protected static long dec(long x) {
return (x <= 0) ? x : x - 1 ;
}
protected Iterator<Node> stepExcludeForwards(Node node, List<Node> excludedNodes) {
Iter<Triple> iter1 = forwardLinks(node, excludedNodes) ;
Iter<Node> r1 = iter1.map(Triple::getObject) ;
return r1 ;
}
protected Iterator<Node> stepExcludeBackwards(Node node, List<Node> excludedNodes) {
Iter<Triple> iter1 = backwardLinks(node, excludedNodes) ;
Iter<Node> r1 = iter1.map(Triple::getSubject) ;
return r1 ;
}
protected Iter<Triple> forwardLinks(Node x, Collection<Node> excludeProperties) {
Iter<Triple> iter1 = Iter.iter(graphFind(x, Node.ANY, Node.ANY)) ;
if ( excludeProperties != null )
iter1 = iter1.filter(new FilterExclude(excludeProperties)) ;
return iter1 ;
}
protected Iter<Triple> backwardLinks(Node x, Collection<Node> excludeProperties) {
Iter<Triple> iter1 = Iter.iter(graphFind(Node.ANY, Node.ANY, x)) ;
if ( excludeProperties != null )
iter1 = iter1.filter(new FilterExclude(excludeProperties)) ;
return iter1 ;
}
protected Iterator<Triple> graphFind(Node s, Node p, Node o) {
return graphFind(graph, s, p, o, context) ;
}
private static Binding binding = BindingFactory.binding() ;
private static Node RDFSmember = RDFS.Nodes.member ;
private static Node ListMember = ListPFunction.nListMember ;
private /*static*/ Iterator<Triple> graphFind(Graph graph, Node s, Node p, Node o, Context context) {
// This is the only place this is called.
// It means we can add property functions here.
// Fast-path common cases.
if ( doingRDFSmember && RDFSmember.equals(p) )
return GraphContainerUtils.rdfsMember(graph, s, o) ;
if ( doingListMember && ListMember.equals(p) )
return GraphList.listMember(graph, s, o) ;
// Potentially just allow the cases above.
//return graph.find(s, p, o) ;
return graphFind2(graph, s, p, o, context) ;
}
/* As general as possible property function inclusion */
private Iterator<Triple> graphFind2(Graph graph, Node s, Node p, Node o, Context context) {
// Not all property functions make sense in property path
// For example, ones taking list arguments only make sense at
// the start or finish, and then only in simple paths
// (e.g. ?x .../propertyFunction ?z)
// which would have been packaged by the optimizer.
if ( p != null && p.isURI() && registry != null ) {
PropertyFunctionFactory f = registry.get(p.getURI()) ;
if ( f != null )
return graphFindWorker(graph, s, f, p, o, context) ;
}
return graph.find(s, p, o) ;
}
private Iterator<Triple> graphFindWorker(Graph graph, Node s, PropertyFunctionFactory f, Node p, Node o, Context context) {
// Expensive?
PropertyFunction pf = f.create(p.getURI()) ;
PropFuncArg sv = arg(s, "S") ;
PropFuncArg ov = arg(o, "O") ;
QueryIterator r = QueryIterRoot.create(new ExecutionContext(context, graph, null, null)) ;
QueryIterator qIter = pf.exec(r, sv, p, ov, new ExecutionContext(ARQ.getContext(), graph, null, null)) ;
if ( ! qIter.hasNext() )
return Iter.nullIterator() ;
List<Triple> array = new ArrayList<>() ;
for ( ; qIter.hasNext() ; ) {
Binding b = qIter.next() ;
Node st = value(sv, b) ;
Node ot = value(ov, b) ;
array.add(Triple.create(st, p, ot)) ;
}
// Materialise so the inner QueryIterators are used up.
return array.iterator() ;
}
private static PropFuncArg arg(Node x, String name) {
if ( x == null || Node.ANY.equals(x) )
{ return new PropFuncArg(Var.alloc(name)) ; }
return new PropFuncArg(x) ;
}
private static Node value(PropFuncArg arg, Binding b) {
Node x = arg.getArg() ;
if ( !Var.isVar(x) )
return x ;
return b.get(Var.alloc(x)) ;
}
}