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package arq.examples.propertyfunction;
import java.util.ArrayList ;
import java.util.Collection ;
import java.util.List ;
import org.apache.jena.graph.Graph ;
import org.apache.jena.graph.Node ;
import org.apache.jena.graph.NodeFactory ;
import org.apache.jena.graph.Triple ;
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.binding.BindingMap ;
import org.apache.jena.sparql.engine.iterator.QueryIterNullIterator ;
import org.apache.jena.sparql.engine.iterator.QueryIterPlainWrapper ;
import org.apache.jena.sparql.engine.iterator.QueryIterSingleton ;
import org.apache.jena.sparql.pfunction.PFuncSimple ;
import org.apache.jena.sparql.util.NodeUtils ;
import org.apache.jena.util.iterator.ExtendedIterator ;
/** Example property function that creates the association between a URI and it's localname.
* See also splitIRI which is more general. This is just an example.
*
* If it is not a URI, then does not match.
*
* Use as:
*
* <pre>
* ?uri ext:localname ?localname
* </pre>
*
* Depending on whether the subject/object are bound when called:
* <ul>
* <li>subject bound, object unbound => assign the local name to variable in object slot</li>
* <li>subject bound, object bound => check the subject has the local name given by object</li>
* <li>subject unbound, object bound => find all URIs in the model (s, p or o) that have that local name</li>
* <li>subject unbound, object unbound => generate all localname for all URI resources in the model</li>
* </ul>
* The two searching forms (subject unbound) are expensive.
* Anything not a URI (subject) or string (object) causes no match.
* */
public class localname extends PFuncSimple
{
@Override
public QueryIterator execEvaluated(Binding binding, Node nodeURI, Node predicate, Node nodeLocalname, ExecutionContext execCxt)
{
if ( ! nodeURI.isVariable() )
return execFixedSubject(nodeURI, nodeLocalname, binding, execCxt) ;
else
return execAllNodes(Var.alloc(nodeURI), nodeLocalname, binding, execCxt) ;
}
// Subject is bound : still two cases: object bound (do a check) and object unbound (assign the local name)
private QueryIterator execFixedSubject(Node nodeURI, Node nodeLocalname, Binding binding, ExecutionContext execCxt)
{
if ( ! nodeURI.isURI() )
// Subject bound but not a URI
return QueryIterNullIterator.create(execCxt) ;
// Subject is bound and a URI - get the localname as a Node
Node localname = NodeFactory.createLiteral(nodeURI.getLocalName()) ;
// Object - unbound variable or a value?
if ( ! nodeLocalname.isVariable() )
{
// Object bound or a query constant. Is it the same as the calculated value?
if ( nodeLocalname.equals(localname) )
// Same
return QueryIterSingleton.create(binding, execCxt) ;
// No - different - no match.
return QueryIterNullIterator.create(execCxt) ;
}
// Object unbound variable - assign the localname to it.
return QueryIterSingleton.create(binding, Var.alloc(nodeLocalname), localname, execCxt) ;
}
// Unbound subject - work hard.
// Still two cases: object bound (filter by localname) and object unbound (generate all localnames for all URIs)
// Warning - will scan the entire graph (there is no localname index) but this example code.
private QueryIterator execAllNodes(Var subjVar, Node nodeLocalname, Binding input, ExecutionContext execCxt)
{
if ( ! nodeLocalname.isVariable() )
{
if ( ! nodeLocalname.isLiteral() )
// Not a variable, not a literal=> can't match
return QueryIterNullIterator.create(execCxt) ;
if( ! NodeUtils.isSimpleString(nodeLocalname) )
return QueryIterNullIterator.create(execCxt) ;
}
//Set bindings = new HashSet() ; // Use a Set if you want unique results.
List<Binding> bindings = new ArrayList<Binding>() ; // Use a list if you want counting results.
Graph graph = execCxt.getActiveGraph() ;
ExtendedIterator<Triple>iter = graph.find(Node.ANY, Node.ANY, Node.ANY) ;
for ( ; iter.hasNext() ; )
{
Triple t = iter.next() ;
slot(bindings, input, t.getSubject(), subjVar, nodeLocalname) ;
slot(bindings, input, t.getPredicate(), subjVar, nodeLocalname) ;
slot(bindings, input, t.getObject(), subjVar, nodeLocalname) ;
}
return new QueryIterPlainWrapper(bindings.iterator(), execCxt) ;
}
private void slot(Collection<Binding> bindings, Binding input, Node node, Var subjVar, Node nodeLocalname)
{
if ( ! node.isURI() ) return ;
Node localname = NodeFactory.createLiteral(node.getLocalName()) ;
if ( nodeLocalname.isVariable() )
{
// Object is an unbound variable.
BindingMap b = BindingFactory.create(input) ;
// Bind a pair for subject and object variables
b.add(Var.alloc(subjVar), node) ;
b.add(Var.alloc(nodeLocalname), localname) ;
bindings.add(b) ;
return ;
}
// Object is a value / bound variable.
if ( ! nodeLocalname.sameValueAs(localname) )
return ;
// Bind subject to this node.
Binding b = BindingFactory.binding(input, subjVar, node) ;
bindings.add(b) ;
}
}