/*
* 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.clerezza.platform.concepts.core;
import java.util.Date;
import java.util.Iterator;
import org.apache.clerezza.platform.concepts.ontologies.CONCEPTS;
import org.apache.clerezza.rdf.core.BNode;
import org.apache.clerezza.rdf.core.Graph;
import org.apache.clerezza.rdf.core.Literal;
import org.apache.clerezza.rdf.core.LiteralFactory;
import org.apache.clerezza.rdf.core.MGraph;
import org.apache.clerezza.rdf.core.NonLiteral;
import org.apache.clerezza.rdf.core.Resource;
import org.apache.clerezza.rdf.core.Triple;
import org.apache.clerezza.rdf.core.TypedLiteral;
import org.apache.clerezza.rdf.core.UriRef;
import org.apache.clerezza.rdf.core.access.NoSuchEntityException;
import org.apache.clerezza.rdf.core.access.TcManager;
import org.apache.clerezza.rdf.core.impl.SimpleMGraph;
import org.apache.clerezza.rdf.core.impl.TripleImpl;
import org.apache.clerezza.rdf.ontologies.DC;
import org.apache.clerezza.rdf.ontologies.OWL;
import org.apache.clerezza.rdf.ontologies.RDF;
import org.apache.clerezza.rdf.ontologies.RDFS;
import org.apache.clerezza.rdf.ontologies.SKOS;
import org.apache.clerezza.rdf.utils.GraphNode;
/**
* This class manages caches of SPARQL query results against a specific EndPoint
* and Graph.
*
* @author hasan
*/
class ConceptCache {
private UriRef sparqlEndPoint;
private UriRef defaultGraph;
private UriRef CONCEPT_CACHE_MGRAPH = new UriRef("urn:x-localinstance:/concept.cache");
/**
* Constructs a {@link ConceptCache} for the specified SPARQL EndPoint and
* Graph.
*
* @param sparqlEndPoint
* the SPARQL EndPoint used in the query.
* @param defaultGraph
* the Graph against which the query was executed.
*
*/
public ConceptCache(UriRef sparqlEndPoint, UriRef defaultGraph) {
this.sparqlEndPoint = sparqlEndPoint;
this.defaultGraph = defaultGraph;
}
/**
* Caches the query results available in the specified Graph under a
* particular search term.
*
* @param searchTerm
* the term used for querying concepts.
* @param parsedGraph
* the Graph which contains query results.
*/
void cache(String searchTerm, Graph parsedGraph) {
MGraph conceptCacheMGraph = getConceptCacheMGraph();
NonLiteral conceptCacheNode = getConceptCacheNode(conceptCacheMGraph);
if (conceptCacheNode != null) {
removeCachedConcepts(searchTerm, conceptCacheNode, conceptCacheMGraph);
}
addCacheEntry(searchTerm, conceptCacheNode, conceptCacheMGraph,
parsedGraph);
}
private MGraph getConceptCacheMGraph() {
MGraph conceptCacheMGraph = null;
TcManager tcManager = TcManager.getInstance();
try {
conceptCacheMGraph = tcManager.getMGraph(CONCEPT_CACHE_MGRAPH);
} catch (NoSuchEntityException nsee) {
conceptCacheMGraph = tcManager.createMGraph(CONCEPT_CACHE_MGRAPH);
}
return conceptCacheMGraph;
}
private NonLiteral getConceptCacheNode(MGraph conceptCacheMGraph) {
Iterator<Triple> conceptCaches = conceptCacheMGraph.filter(
null, RDF.type, CONCEPTS.ConceptCache);
while (conceptCaches.hasNext()) {
NonLiteral conceptCacheNode = conceptCaches.next().getSubject();
if (!conceptCacheMGraph.filter(conceptCacheNode,
CONCEPTS.sparqlEndPoint, sparqlEndPoint).hasNext()) {
continue;
}
if (defaultGraph != null) {
if (!conceptCacheMGraph.filter(conceptCacheNode,
CONCEPTS.defaultGraph, defaultGraph).hasNext()) {
continue;
}
}
return conceptCacheNode;
}
return null;
}
private void removeCachedConcepts(String searchTerm,
NonLiteral conceptCacheNode, MGraph conceptCacheMGraph) {
NonLiteral conceptCacheEntryNode = getConceptCacheEntryNode(
searchTerm, conceptCacheNode, conceptCacheMGraph);
if (conceptCacheEntryNode == null) {
return;
}
GraphNode conceptCacheEntryGraphNode = new GraphNode(
conceptCacheEntryNode, conceptCacheMGraph);
removeCachedConcepts(conceptCacheEntryGraphNode);
conceptCacheMGraph.remove(new TripleImpl(conceptCacheNode,
CONCEPTS.cacheEntry, conceptCacheEntryNode));
}
private NonLiteral getConceptCacheEntryNode(String searchTerm,
NonLiteral conceptCacheNode, MGraph conceptCacheMGraph) {
TypedLiteral searchLiteral = LiteralFactory.getInstance()
.createTypedLiteral(searchTerm);
Iterator<Triple> cacheEntries = conceptCacheMGraph.filter(
conceptCacheNode, CONCEPTS.cacheEntry, null);
while (cacheEntries.hasNext()) {
NonLiteral conceptCacheEntryNode = (NonLiteral) cacheEntries.next()
.getObject();
if (!conceptCacheMGraph.filter(conceptCacheEntryNode,
CONCEPTS.searchTerm, searchLiteral).hasNext()) {
continue;
}
return conceptCacheEntryNode;
}
return null;
}
private void removeCachedConcepts(GraphNode conceptCacheEntryGraphNode) {
Iterator<Resource> searchResults =
conceptCacheEntryGraphNode.getObjects(CONCEPTS.searchResult);
while (searchResults.hasNext()) {
Resource concept = searchResults.next();
GraphNode conceptGraphNode = new GraphNode(concept,
conceptCacheEntryGraphNode.getGraph());
conceptGraphNode.deleteProperties(OWL.sameAs);
conceptGraphNode.deleteProperties(RDFS.comment);
conceptGraphNode.deleteProperties(SKOS.prefLabel);
conceptGraphNode.deleteProperties(RDF.type);
}
conceptCacheEntryGraphNode.deleteProperties(CONCEPTS.searchResult);
conceptCacheEntryGraphNode.deleteProperties(DC.date);
conceptCacheEntryGraphNode.deleteProperties(CONCEPTS.searchTerm);
conceptCacheEntryGraphNode.deleteProperties(RDF.type);
}
private void addCacheEntry(String searchTerm, NonLiteral conceptCacheNode,
MGraph conceptCacheMGraph, Graph parsedGraph) {
GraphNode conceptCacheGraphNode = null;
if (conceptCacheNode == null) {
conceptCacheGraphNode = addConceptCacheNode(conceptCacheMGraph);
} else {
conceptCacheGraphNode = new GraphNode(conceptCacheNode,
conceptCacheMGraph);
}
GraphNode conceptCacheEntryGraphNode = new GraphNode(new BNode(),
conceptCacheMGraph);
conceptCacheGraphNode.addProperty(CONCEPTS.cacheEntry,
conceptCacheEntryGraphNode.getNode());
conceptCacheEntryGraphNode.addProperty(RDF.type, CONCEPTS.SearchTerm);
conceptCacheEntryGraphNode.addProperty(CONCEPTS.searchTerm,
LiteralFactory.getInstance().createTypedLiteral(searchTerm));
conceptCacheEntryGraphNode.addProperty(DC.date,
LiteralFactory.getInstance().createTypedLiteral(new Date()));
Iterator<Triple> concepts = parsedGraph.filter(null, RDF.type, SKOS.Concept);
while (concepts.hasNext()) {
conceptCacheEntryGraphNode.addProperty(CONCEPTS.searchResult,
concepts.next().getSubject());
}
conceptCacheMGraph.addAll(parsedGraph);
}
private GraphNode addConceptCacheNode(MGraph conceptCacheMGraph) {
GraphNode conceptCacheGraphNode = new GraphNode(new BNode(),
conceptCacheMGraph);
conceptCacheGraphNode.addProperty(RDF.type, CONCEPTS.ConceptCache);
conceptCacheGraphNode.addProperty(CONCEPTS.sparqlEndPoint,
sparqlEndPoint);
if (defaultGraph != null) {
conceptCacheGraphNode.addProperty(CONCEPTS.defaultGraph,
defaultGraph);
}
return conceptCacheGraphNode;
}
/**
* Retrieves concepts from the cache stored under the specified search term.
* Cache entries are invalid if they are older than the specified date.
*
* @param searchTerm
* the search term under which the concepts are cached.
* @param acceptableOldestCachingDate
* the Date before which a cache entry is considered invalid.
* @return
* an {@link MGraph} containing the valid cached concepts.
*/
MGraph retrieve(String searchTerm, Date acceptableOldestCachingDate) {
MGraph conceptCacheMGraph = getConceptCacheMGraph();
NonLiteral conceptCacheNode = getConceptCacheNode(conceptCacheMGraph);
if (conceptCacheNode == null) {
return null;
}
NonLiteral conceptCacheEntryNode = getConceptCacheEntryNode(searchTerm,
conceptCacheNode, conceptCacheMGraph);
if (conceptCacheEntryNode == null) {
return null;
}
GraphNode conceptCacheEntryGraphNode = new GraphNode(
conceptCacheEntryNode, conceptCacheMGraph);
Date cachingDate = getCachingDate(conceptCacheEntryGraphNode);
if (cachingDate == null || cachingDate.before(acceptableOldestCachingDate)) {
removeCachedConcepts(conceptCacheEntryGraphNode);
conceptCacheMGraph.remove(new TripleImpl(conceptCacheNode,
CONCEPTS.cacheEntry, conceptCacheEntryNode));
return null;
}
return getCachedConcepts(conceptCacheEntryGraphNode);
}
private Date getCachingDate(GraphNode conceptCacheEntryGraphNode) {
Iterator<Literal> cachingDates = conceptCacheEntryGraphNode.getLiterals(
DC.date);
if (cachingDates.hasNext()) {
return LiteralFactory.getInstance().createObject(Date.class,
(TypedLiteral) cachingDates.next());
}
return null;
}
private MGraph getCachedConcepts(GraphNode conceptCacheEntryGraphNode) {
MGraph resultMGraph = new SimpleMGraph();
MGraph conceptCacheMGraph = (MGraph) conceptCacheEntryGraphNode.getGraph();
NonLiteral conceptCacheNode = (NonLiteral) conceptCacheEntryGraphNode.getNode();
Iterator<Triple> triples = conceptCacheMGraph.filter(
conceptCacheNode, CONCEPTS.searchResult, null);
while (triples.hasNext()) {
UriRef concept = (UriRef) triples.next().getObject();
GraphNode graphNode = new GraphNode(concept, conceptCacheMGraph);
resultMGraph.add(new TripleImpl(concept, RDF.type, SKOS.Concept));
Iterator<Literal> prefLabelStatements = graphNode.getLiterals(SKOS.prefLabel);
while (prefLabelStatements.hasNext()) {
resultMGraph.add(new TripleImpl(concept, SKOS.prefLabel,
prefLabelStatements.next()));
}
Iterator<Literal> commentStatements = graphNode.getLiterals(RDFS.comment);
while (commentStatements.hasNext()) {
resultMGraph.add(new TripleImpl(concept, RDFS.comment,
commentStatements.next()));
}
Iterator<UriRef> sameAsStatements = graphNode.getUriRefObjects(OWL.sameAs);
while (sameAsStatements.hasNext()) {
resultMGraph.add(new TripleImpl(concept, OWL.sameAs,
sameAsStatements.next()));
}
}
return resultMGraph;
}
}