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extended the TriplePatternInterface to support anonymous variables; see
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LinkedDataFragments#28
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Olaf Hartig committed Dec 31, 2015
1 parent f03b8ed commit 29b2e70
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Showing 15 changed files with 296 additions and 164 deletions.
38 changes: 22 additions & 16 deletions src/org/linkeddatafragments/datasource/AbstractRequestProcessorForTriplePatterns.java
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Original file line number Diff line number Diff line change
Expand Up @@ -13,40 +13,46 @@
* Base class for implementations of {@link IFragmentRequestProcessor} that
* process {@link TriplePatternFragmentRequest}s.
*
* @param <TermType> type for representing RDF terms in triple patterns
* @param <VarType> type for representing specific variables in triple patterns
* @param <CTT>
* type for representing constants in triple patterns (i.e., URIs and
* literals)
* @param <NVT>
* type for representing named variables in triple patterns
* @param <AVT>
* type for representing anonymous variables in triple patterns (i.e.,
* variables denoted by a blank node)
*
* @author <a href="http://olafhartig.de">Olaf Hartig</a>
*/
public abstract class
AbstractRequestProcessorForTriplePatterns<TermType,VarType>
AbstractRequestProcessorForTriplePatterns<CTT,NVT,AVT>
extends AbstractRequestProcessor
{
@Override
protected final Worker<TermType,VarType> getWorker(
protected final Worker<CTT,NVT,AVT> getWorker(
final LinkedDataFragmentRequest request )
throws IllegalArgumentException
{
if ( request instanceof TriplePatternFragmentRequest<?,?> ) {
if ( request instanceof TriplePatternFragmentRequest<?,?,?> ) {
@SuppressWarnings("unchecked")
final TriplePatternFragmentRequest<TermType,VarType> tpfRequest =
(TriplePatternFragmentRequest<TermType,VarType>) request;
final TriplePatternFragmentRequest<CTT,NVT,AVT> tpfRequest =
(TriplePatternFragmentRequest<CTT,NVT,AVT>) request;
return getTPFSpecificWorker( tpfRequest );
}
else
throw new IllegalArgumentException( request.getClass().getName() );
}

abstract protected Worker<TermType,VarType> getTPFSpecificWorker(
final TriplePatternFragmentRequest<TermType,VarType> request )
abstract protected Worker<CTT,NVT,AVT> getTPFSpecificWorker(
final TriplePatternFragmentRequest<CTT,NVT,AVT> request )
throws IllegalArgumentException;


abstract static protected class Worker<TermType,VarType>
abstract static protected class Worker<CTT,NVT,AVT>
extends AbstractRequestProcessor.Worker
{
public Worker(
final TriplePatternFragmentRequest<TermType,VarType> request )
final TriplePatternFragmentRequest<CTT,NVT,AVT> request )
{
super( request );
}
Expand All @@ -63,8 +69,8 @@ public LinkedDataFragment createRequestedFragment()
offset = 0L;

@SuppressWarnings("unchecked")
final TriplePatternFragmentRequest<TermType,VarType> tpfRequest =
(TriplePatternFragmentRequest<TermType,VarType>) request;
final TriplePatternFragmentRequest<CTT,NVT,AVT> tpfRequest =
(TriplePatternFragmentRequest<CTT,NVT,AVT>) request;

return createFragment( tpfRequest.getSubject(),
tpfRequest.getPredicate(),
Expand All @@ -73,9 +79,9 @@ public LinkedDataFragment createRequestedFragment()
}

abstract protected LinkedDataFragment createFragment(
final TriplePatternElement<TermType,VarType> subj,
final TriplePatternElement<TermType,VarType> pred,
final TriplePatternElement<TermType,VarType> obj,
final TriplePatternElement<CTT,NVT,AVT> subj,
final TriplePatternElement<CTT,NVT,AVT> pred,
final TriplePatternElement<CTT,NVT,AVT> obj,
final long offset,
final long limit )
throws IllegalArgumentException;
Expand Down
28 changes: 15 additions & 13 deletions src/org/linkeddatafragments/datasource/hdt/HdtBasedRequestProcessorForTPFs.java
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Original file line number Diff line number Diff line change
Expand Up @@ -27,7 +27,7 @@
* @author <a href="http://olafhartig.de">Olaf Hartig</a>
*/
public class HdtBasedRequestProcessorForTPFs
extends AbstractRequestProcessorForTriplePatterns<RDFNode,String>
extends AbstractRequestProcessorForTriplePatterns<RDFNode,String,String>
{
protected final HDT datasource;
protected final NodeDictionary dictionary;
Expand All @@ -46,38 +46,40 @@ public HdtBasedRequestProcessorForTPFs( String hdtFile ) throws IOException

@Override
protected Worker getTPFSpecificWorker(
final TriplePatternFragmentRequest<RDFNode,String> request )
final TriplePatternFragmentRequest<RDFNode,String,String> request )
throws IllegalArgumentException
{
return new Worker( request );
}


protected class Worker
extends AbstractRequestProcessorForTriplePatterns.Worker<RDFNode,String>
extends AbstractRequestProcessorForTriplePatterns.Worker<RDFNode,String,String>
{
public Worker( final TriplePatternFragmentRequest<RDFNode,String> req )
public Worker(
final TriplePatternFragmentRequest<RDFNode,String,String> req )
{
super( req );
}

@Override
protected LinkedDataFragment createFragment(
final TriplePatternElement<RDFNode,String> subject,
final TriplePatternElement<RDFNode,String> predicate,
final TriplePatternElement<RDFNode,String> object,
final long offset,
final long limit )
final TriplePatternElement<RDFNode,String,String> subject,
final TriplePatternElement<RDFNode,String,String> predicate,
final TriplePatternElement<RDFNode,String,String> object,
final long offset,
final long limit )
{
// FIXME: The following algorithm is incorrect for cases in which
// the requested triple pattern contains a specific variable
// multiple times (e.g., ?x foaf:knows ?x ).
// multiple times;
// e.g., (?x foaf:knows ?x ) or (_:bn foaf:knows _:bn)
// see https://github.com/LinkedDataFragments/Server.Java/issues/23

// look up the result from the HDT datasource)
int subjectId = subject.isVariable() ? 0 : dictionary.getIntID(subject.asTerm().asNode(), TripleComponentRole.SUBJECT);
int predicateId = predicate.isVariable() ? 0 : dictionary.getIntID(predicate.asTerm().asNode(), TripleComponentRole.PREDICATE);
int objectId = object.isVariable() ? 0 : dictionary.getIntID(object.asTerm().asNode(), TripleComponentRole.OBJECT);
int subjectId = subject.isVariable() ? 0 : dictionary.getIntID(subject.asConstantTerm().asNode(), TripleComponentRole.SUBJECT);
int predicateId = predicate.isVariable() ? 0 : dictionary.getIntID(predicate.asConstantTerm().asNode(), TripleComponentRole.PREDICATE);
int objectId = object.isVariable() ? 0 : dictionary.getIntID(object.asConstantTerm().asNode(), TripleComponentRole.OBJECT);

if (subjectId < 0 || predicateId < 0 || objectId < 0) {
return createEmptyTriplePatternFragment();
Expand Down
28 changes: 15 additions & 13 deletions src/org/linkeddatafragments/datasource/index/IndexRequestProcessorForTPFs.java
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Original file line number Diff line number Diff line change
Expand Up @@ -28,7 +28,7 @@
* @author <a href="http://olafhartig.de">Olaf Hartig</a>
*/
public class IndexRequestProcessorForTPFs
extends AbstractRequestProcessorForTriplePatterns<RDFNode,String>
extends AbstractRequestProcessorForTriplePatterns<RDFNode,String,String>
{
final static String RDF = "http://www.w3.org/1999/02/22-rdf-syntax-ns#";
final static String RDFS = "http://www.w3.org/2000/01/rdf-schema#";
Expand Down Expand Up @@ -58,40 +58,42 @@ public IndexRequestProcessorForTPFs(

@Override
protected Worker getTPFSpecificWorker(
final TriplePatternFragmentRequest<RDFNode,String> request )
final TriplePatternFragmentRequest<RDFNode,String,String> request )
throws IllegalArgumentException
{
return new Worker( request );
}


protected class Worker
extends AbstractRequestProcessorForTriplePatterns.Worker<RDFNode,String>
extends AbstractRequestProcessorForTriplePatterns.Worker<RDFNode,String,String>
{
public Worker( final TriplePatternFragmentRequest<RDFNode,String> req )
public Worker(
final TriplePatternFragmentRequest<RDFNode,String,String> req )
{
super( req );
}

@Override
protected LinkedDataFragment createFragment(
final TriplePatternElement<RDFNode,String> s,
final TriplePatternElement<RDFNode,String> p,
final TriplePatternElement<RDFNode,String> o,
final long offset,
final long limit )
final TriplePatternElement<RDFNode,String,String> s,
final TriplePatternElement<RDFNode,String,String> p,
final TriplePatternElement<RDFNode,String,String> o,
final long offset,
final long limit )
{
// FIXME: The following algorithm is incorrect for cases in which
// the requested triple pattern contains a specific variable
// multiple times (e.g., ?x foaf:knows ?x ).
// multiple times;
// e.g., (?x foaf:knows ?x ) or (_:bn foaf:knows _:bn)
// see https://github.com/LinkedDataFragments/Server.Java/issues/25

final Resource subject = s.isVariable() ? null
: s.asTerm().asResource();
: s.asConstantTerm().asResource();
final Property predicate = p.isVariable() ? null
: ResourceFactory.createProperty(p.asTerm().asResource().getURI());
: ResourceFactory.createProperty(p.asConstantTerm().asResource().getURI());
final RDFNode object = o.isVariable() ? null
: o.asTerm();
: o.asConstantTerm();

StmtIterator listStatements = model.listStatements(subject, predicate, object);
Model result = ModelFactory.createDefaultModel();
Expand Down
28 changes: 15 additions & 13 deletions src/org/linkeddatafragments/datasource/tdb/JenaTDBBasedRequestProcessorForTPFs.java
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Original file line number Diff line number Diff line change
Expand Up @@ -30,7 +30,7 @@
* @author <a href="http://olafhartig.de">Olaf Hartig</a>
*/
public class JenaTDBBasedRequestProcessorForTPFs
extends AbstractRequestProcessorForTriplePatterns<RDFNode,String>
extends AbstractRequestProcessorForTriplePatterns<RDFNode,String,String>
{
private final Dataset tdb;
private final String sparql = "CONSTRUCT WHERE { ?s ?p ?o } " +
Expand All @@ -43,44 +43,46 @@ public class JenaTDBBasedRequestProcessorForTPFs

@Override
protected Worker getTPFSpecificWorker(
final TriplePatternFragmentRequest<RDFNode,String> request )
final TriplePatternFragmentRequest<RDFNode,String,String> request )
throws IllegalArgumentException
{
return new Worker( request );
}


protected class Worker
extends AbstractRequestProcessorForTriplePatterns.Worker<RDFNode,String>
extends AbstractRequestProcessorForTriplePatterns.Worker<RDFNode,String,String>
{
public Worker( final TriplePatternFragmentRequest<RDFNode,String> req )
public Worker(
final TriplePatternFragmentRequest<RDFNode,String,String> req )
{
super( req );
}

@Override
protected LinkedDataFragment createFragment(
final TriplePatternElement<RDFNode,String> subject,
final TriplePatternElement<RDFNode,String> predicate,
final TriplePatternElement<RDFNode,String> object,
final long offset,
final long limit )
final TriplePatternElement<RDFNode,String,String> subject,
final TriplePatternElement<RDFNode,String,String> predicate,
final TriplePatternElement<RDFNode,String,String> object,
final long offset,
final long limit )
{
// FIXME: The following algorithm is incorrect for cases in which
// the requested triple pattern contains a specific variable
// multiple times (e.g., ?x foaf:knows ?x ).
// multiple times;
// e.g., (?x foaf:knows ?x ) or (_:bn foaf:knows _:bn)
// see https://github.com/LinkedDataFragments/Server.Java/issues/24

Model model = tdb.getDefaultModel();
QuerySolutionMap map = new QuerySolutionMap();
if ( ! subject.isVariable() ) {
map.add("s", subject.asTerm());
map.add("s", subject.asConstantTerm());
}
if ( ! predicate.isVariable() ) {
map.add("p", predicate.asTerm());
map.add("p", predicate.asConstantTerm());
}
if ( ! object.isVariable() ) {
map.add("o", object.asTerm());
map.add("o", object.asConstantTerm());
}

query.setOffset(offset);
Expand Down
16 changes: 8 additions & 8 deletions src/org/linkeddatafragments/fragments/tpf/TPFRequestParser.java
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Original file line number Diff line number Diff line change
Expand Up @@ -16,13 +16,13 @@
*
* @author <a href="http://olafhartig.de">Olaf Hartig</a>
*/
public class TPFRequestParser<TermType,VarType>
public class TPFRequestParser<ConstantTermType,NamedVarType,AnonVarType>
extends FragmentRequestParserBase
{
public final TriplePatternElementParser<TermType,VarType> elmtParser;
public final TriplePatternElementParser<ConstantTermType,NamedVarType,AnonVarType> elmtParser;

public TPFRequestParser(
final TriplePatternElementParser<TermType,VarType> elmtParser )
final TriplePatternElementParser<ConstantTermType,NamedVarType,AnonVarType> elmtParser )
{
this.elmtParser = elmtParser;
}
Expand All @@ -47,7 +47,7 @@ public Worker( final HttpServletRequest request,
public LinkedDataFragmentRequest createFragmentRequest()
throws IllegalArgumentException
{
return new TriplePatternFragmentRequestImpl<TermType,VarType>(
return new TriplePatternFragmentRequestImpl<ConstantTermType,NamedVarType,AnonVarType>(
getFragmentURL(),
getDatasetURL(),
pageNumberWasRequested,
Expand All @@ -57,22 +57,22 @@ public LinkedDataFragmentRequest createFragmentRequest()
getObject() );
}

public TriplePatternElement<TermType,VarType> getSubject() {
public TriplePatternElement<ConstantTermType,NamedVarType,AnonVarType> getSubject() {
return getParameterAsTriplePatternElement(
TriplePatternFragmentRequest.PARAMETERNAME_SUBJ );
}

public TriplePatternElement<TermType,VarType> getPredicate() {
public TriplePatternElement<ConstantTermType,NamedVarType,AnonVarType> getPredicate() {
return getParameterAsTriplePatternElement(
TriplePatternFragmentRequest.PARAMETERNAME_PRED );
}

public TriplePatternElement<TermType,VarType> getObject() {
public TriplePatternElement<ConstantTermType,NamedVarType,AnonVarType> getObject() {
return getParameterAsTriplePatternElement(
TriplePatternFragmentRequest.PARAMETERNAME_OBJ );
}

public TriplePatternElement<TermType,VarType>
public TriplePatternElement<ConstantTermType,NamedVarType,AnonVarType>
getParameterAsTriplePatternElement( final String paramName )
{
final String parameter = request.getParameter( paramName );
Expand Down
2 changes: 1 addition & 1 deletion src/org/linkeddatafragments/fragments/tpf/TPFRequestParserForJenaBackends.java
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Original file line number Diff line number Diff line change
Expand Up @@ -10,7 +10,7 @@
* @author <a href="http://olafhartig.de">Olaf Hartig</a>
*/
public class TPFRequestParserForJenaBackends
extends TPFRequestParser<RDFNode,String>
extends TPFRequestParser<RDFNode,String,String>
{
private static TPFRequestParserForJenaBackends instance = null;

Expand Down
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