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ARQ is a SPARQL 1.1 query engine for Apache Jena
/**
* 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.util ;
import static org.apache.jena.atlas.lib.tuple.TupleFactory.tuple ;
import java.util.ArrayList ;
import java.util.Collection ;
import java.util.Iterator ;
import java.util.List ;
import org.apache.jena.atlas.lib.tuple.Tuple ;
import org.apache.jena.graph.Graph ;
import org.apache.jena.graph.Node ;
import org.apache.jena.graph.Triple ;
import org.apache.jena.sparql.core.DatasetGraph ;
import org.apache.jena.sparql.core.Quad ;
import org.apache.jena.sparql.util.NodeUtils.EqualityTest ;
// Needs to be back tracking?
/** Simple isomorphism testing
* This code is simple and slow.
* For graphs, the Graph isomorphism code in Jena is much better (better tested, better performance)
* This code can work on any tuples of nodes.
*/
public class IsoMatcher
{
// Possible speed ups
// A/ Phase 1 - do all non-bNode tuples. / Phase 2 : all tuples with a bNode
// B/ turn tuples2 into a map, keyed by (1) constants or (2) first term.
static boolean DEBUG = false ;
private final List> tuples1 ;
private final List> tuples2 ;
// private final Map mapping = new HashMap<>();
// private final Queue> causes = new LinkedList<>() ;
private final EqualityTest nodeTest ;
static class Mapping {
final Node node1 ;
final Node node2 ;
final Mapping parent ;
static Mapping rootMapping = new Mapping(null, null, null) ;
public Mapping(Mapping parent, Node node1, Node node2) {
super() ;
this.parent = parent ;
this.node1 = node1 ;
this.node2 = node2 ;
}
public boolean mapped(Node node) {
return map(node) != null ;
}
public boolean revmapped(Node node) {
return revmap(node) != null ;
}
public Node map(Node node) {
Mapping mapping = this ;
while (mapping != rootMapping) {
if ( mapping.node1.equals(node) )
return mapping.node2 ;
mapping = mapping.parent ;
}
return null ;
}
// Reverse mapping.
public Node revmap(Node node) {
Mapping mapping = this ;
while (mapping != rootMapping) {
if ( mapping.node2.equals(node) )
return mapping.node1 ;
mapping = mapping.parent ;
}
return null ;
}
@Override
public String toString() {
StringBuilder sbuff = new StringBuilder() ;
Mapping mapping = this ;
while (mapping != rootMapping) {
sbuff.append("{" + mapping.node1 + " => " + mapping.node2 + "}") ;
mapping = mapping.parent ;
}
sbuff.append("{}") ;
return sbuff.toString() ;
}
}
static class Cause {
final Tuple tuple ;
final Mapping mapping ;
public Cause(Tuple tuple, Mapping mapping) {
super() ;
this.tuple = tuple ;
this.mapping = mapping ;
}
}
public static boolean isomorphic(Graph g1, Graph g2) {
List> x1 = tuplesTriples(g1.find(null, null, null)) ;
List> x2 = tuplesTriples(g2.find(null, null, null)) ;
IsoMatcher matcher = new IsoMatcher(x1, x2, NodeUtils.sameTerm) ;
return matcher.match() ;
}
public static boolean isomorphic(DatasetGraph dsg1, DatasetGraph dsg2) {
List> x1 = tuplesQuads(dsg1.find()) ;
List> x2 = tuplesQuads(dsg2.find()) ;
IsoMatcher matcher = new IsoMatcher(x1, x2, NodeUtils.sameTerm) ;
return matcher.match() ;
}
public static boolean isomorphic(List> x1, List> x2) {
x1 = new ArrayList<>(x1) ;
x2 = new ArrayList<>(x2) ;
IsoMatcher matcher = new IsoMatcher(x1, x2, NodeUtils.sameTerm) ;
return matcher.match() ;
}
private static List> tuplesTriples(Iterator iter) {
List> tuples = new ArrayList<>() ;
for ( ; iter.hasNext() ; ) {
Triple t = iter.next() ;
Tuple tuple = tuple(t.getSubject(), t.getPredicate(), t.getObject()) ;
tuples.add(tuple) ;
}
return tuples ;
}
private static List> tuplesQuads(Iterator iter) {
List> tuples = new ArrayList<>() ;
for ( ; iter.hasNext() ; ) {
Quad q = iter.next() ;
Tuple tuple = tuple(q.getGraph(), q.getSubject(), q.getPredicate(), q.getObject()) ;
tuples.add(tuple) ;
}
return tuples ;
}
private IsoMatcher(List> g1, List> g2, EqualityTest nodeTest) {
this.tuples1 = g1 ;
this.tuples2 = g2 ;
this.nodeTest = nodeTest ;
}
// May MUTATE tuples1 or tuples2
private boolean match() {
return match(tuples1, tuples2, Mapping.rootMapping) ;
}
private boolean match(List> tuples1, List> tuples2, Mapping mapping) {
if ( DEBUG ) {
System.out.println("match: ") ;
System.out.println(" "+tuples1) ;
System.out.println(" "+tuples2) ;
System.out.println(" "+mapping) ;
}
if ( tuples1.size() != tuples2.size() )
return false;
List> tuples = new ArrayList<>(tuples1) ; // Copy, mutate
for ( Tuple t1 : tuples1 ) {
if ( DEBUG )
System.out.println(" t1 = "+t1) ;
tuples.remove(t1) ;
List causes = match(t1, tuples2, mapping) ;
for ( Cause c : causes ) {
if ( DEBUG )
System.out.println(" Try: "+c.mapping) ;
// Try t1 -> t2
Tuple t2 = c.tuple ;
tuples2.remove(t2) ;
if ( tuples2.isEmpty() )
return true ;
if ( match(tuples, tuples2, c.mapping) ) {
if ( DEBUG )
System.out.println("Yes") ;
return true ;
}
if ( DEBUG )
System.out.println("No") ;
tuples2.add(t2) ;
}
return false ;
}
// The empty-empty case
return true ;
}
private List match(Tuple t1, Collection> g2, Mapping mapping) {
List matches = new ArrayList<>() ;
for ( Tuple t2 : g2 ) {
// No - multiple bNodes.
Mapping step = gen(t1, t2, mapping) ;
if (step != null) {
Cause c = new Cause(t2, step) ;
matches.add(c) ;
}
}
return matches ;
}
// Maybe several mappings!
private Mapping gen(Tuple t1, Tuple t2, Mapping _mapping) {
if ( t1.len() != t2.len() )
return null ;
Mapping mapping = _mapping ;
for ( int i = 0 ; i < t1.len() ; i++ ) {
Node n1 = t1.get(i) ;
Node n2 = t2.get(i) ;
if ( ! nodeTest.equal(n1, n2) ) {
mapping = gen(n1, n2, mapping) ;
if ( mapping == null )
return null ;
}
}
return mapping ;
}
private Mapping gen(Node x1, Node x2, Mapping mapping) {
if ( x1.isBlank() && x2.isBlank() ) {
// Is x1 already mapped?
Node z = mapping.map(x1) ;
if ( z != null )
// Already mapped
return (nodeTest.equal(x2, z)) ? mapping : null ;
// Check reverse
if ( mapping.revmapped(x2) )
return null ;
return new Mapping(mapping, x1, x2) ;
}
return null ;
}
}
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