You'll still have to clean up structures. SPIN for this is encoding the
query in RDF but the rewriting of that structure needs the same (in the
abstract) processing. You may be able to do it with a series of SPARQL
Updates (that's speculation).
Andy
On 29/01/16 00:26, Carlo.Allocca wrote:
Dear Martynas,
Thank you very much for your help.
At the moment, I am trying what Andy suggested.
I hope to make it. Otherwise, I will look at SPIN API.
Many Thanks,
Best Regards,
Carlo
On 28 Jan 2016, at 23:48, Martynas Jusevičius <[email protected]> wrote:
You could do it using SPIN API as well: http://spinrdf.org/sp.html
On Thu, Jan 28, 2016 at 7:39 PM, Carlo.Allocca <[email protected]> wrote:
Dear Andy,
Thank you very much for your promtly reply.
I need a little bit of exploring and thinking to apply what you suggested.
Indeed, I will look at each single info you pointed out.
I will keep this thread updated.
Many Thanks,
Best Regards,
Carlo
On 28 Jan 2016, at 18:29, Andy Seaborne <[email protected]> wrote:
The approach I would take is to do this is multiple passes:
1/ remove from ElementPathBlock
2/ Look for elements that are now "empty"
e.g ElementFilter with empty
but also as there one arm of a UNION.
(2) is only one pass as the rewrite is done bottom up.
I would do this as a transformation rather than modifying the syntax tree in
place.
org.apache.jena.sparql.syntax.syntaxtransform
See also
ElementTransformCleanGroupsOfOne
which might be helpful to understand - its doing something different though.
It might be easier to work on the algebra, it's more regular. Then use
OpAsQuery to turn algebnra into a Query.
I could not figure out how to remove the associated FILTER
when visit(ElementFilter el) as below.
because you need to alter the ElementUnion which holds the ElementFilter.
{...} UNION {} will include a blank row for the {} on the right hand side.
Andy
On 28/01/16 13:14, Carlo.Allocca wrote:
Dear All,
I am using Jena for my project and I would like to submit the following
question: How to remove consistently a triple pattern given a SPARQL query?
EXAMPLE:
For example, considering the query “qString1” and the tp=“?boss ex:isBossOf
?ind .”
I need to remove tp from qString1, obtaining qString1. For “Consistently” I
mean that the clause FILTER gets affected (as it contains var that appears in
the triple pattern too), therefore it needs to be deleted too.
String qString1 =
" SELECT DISTINCT ?ind ?boss ?g where "
+ "{ "
+ " ?ind rdf:type ex:AssociatedResearcher ."
+ " {?ind rdf:type ?z. } UNION "
+ " {?boss ex:isBossOf ?ind . Filter(?boss=\”rossi\”)} "
+ "}";
String qString2 =
" SELECT DISTINCT ?ind ?boss ?g “
+ “WHERE "
+ "{ "
+ " ?ind rdf:type ex:AssociatedResearcher ."
+ " {?ind rdf:type ?z. } UNION "
+ " {} "
+ "}";
The solution that I am trying to implement is based on a visitor
“SQRemoveTripleVisitor extends ElementVisitorBase”.
It is quite straightforward to remove the triple pattern when
visit(ElementPathBlock el)
@Override
public void visit(ElementPathBlock el) {
if (el == null) {
throw new
IllegalStateException("[SQRemoveTripleVisitor::visit(ElementPathBlock el)] The
ElementPathBlock is null!!");
}
ListIterator<TriplePath> it = el.getPattern().iterator();
while (it.hasNext()) {
final TriplePath tp1 = it.next();
if (this.tp != null) {
if (this.tp.matches(tp1.asTriple())) {
it.remove();
}
}
}
}
I could not figure out how to remove the associated FILTER when
visit(ElementFilter el) as below.
@Override
public void visit(ElementFilter el) {
//...get the variables of the FILTER expression
Expr filterExp = el.getExpr();//.getVarsMentioned().contains(el);
Set<Var> expVars = filterExp.getVarsMentioned();
//...get the variables of the triple pattern that we want to delete
Set<Var> tpVars = new HashSet();
Node subj = this.tp.getSubject();
if (subj.isVariable()) {
tpVars.add((Var) subj);
}
Node pred = this.tp.getPredicate();
if (pred.isVariable()) {
tpVars.add((Var) pred);
}
Node obj = this.tp.getObject();
if (obj.isVariable()) {
tpVars.add((Var) obj);
}
//...check whether the FILTER expression contains any of the triple
pattern’s variable
for(Var var:expVars){
//…if it does then we have to delete the entire FILTER expression
if(tpVars.contains(var)){
System.out.println("[SQRemoveTripleVisitor::visit(ElementFilter el)]
I NEED TO REMOVE THE FILTER!!!!!! ");
}
}
}
Please, may I ask for any help or idea on how to remove the filter?
Many Thanks in advance.
Best Regards,
Carlo
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