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 <carlo.allo...@open.ac.uk> 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 <a...@apache.org> 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
>>>
>>>
>>> -- The Open University is incorporated by Royal Charter (RC 000391), an
>>> exempt charity in England & Wales and a charity registered in Scotland (SC
>>> 038302). The Open University is authorised and regulated by the Financial
>>> Conduct Authority.
>>>
>>
>
