Dear Andy and All,
I tried to use as many suggested info as I could. As result, I obtained the
following:
I am implementing a public class RemoveOpTransform implements ElementTransform.
And, again It is quite straightforward to remove the triple pattern from the
ElementPathBlock
@Override
public Element transform(ElementPathBlock eltPB) {
System.out.println("[RemoveOpTransform::transform(ElementPathBlock
arg0)] " + eltPB.toString());
Iterator<TriplePath> l = eltPB.patternElts();
while (l.hasNext()) {
TriplePath tp = l.next();
if (tp.asTriple().matches(this.triple)) {
l.remove();
System.out.println("[RemoveOpTransform::transform(ElementPathBlock arg0)]
TRIPLE MAP JUST REMOVED!!! ");
System.out.println("");
return this.transform(eltPB);//eltPB;
}
}
return eltPB;
}
But I could not figure out how to remove the associated FILTER when
transform(ElementFilter arg0, Expr arg1) as below
@Override
public Element transform(ElementFilter arg0, Expr arg1) {
//...get the variables of the triple pattern that we want to delete
Set<Var> tpVars = new HashSet();
Node subj = this.triple.getSubject();
if (subj.isVariable()) {
tpVars.add((Var) subj);
}
Node pred = this.triple.getPredicate();
if (pred.isVariable()) {
tpVars.add((Var) pred);
}
Node obj = this.triple.getObject();
if (obj.isVariable()) {
tpVars.add((Var) obj);
}
//...get the variables of the FILTER expression
Set<Var> expVars = arg1.getVarsMentioned();
//...check whether the FILTER expression contains any of the triple
pattern 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
arg0)] FILTER TO BE REMOVED!!!HOW? ");
System.out.println("");
}
}
return arg0;
}
It appears to me that I am at the same point of the previous approach.
What am I doing wrong or missing? Or what I should ready to figure it out?
Thank you very much for your kind help and support.
Best Regards,
Carlo
> On 29 Jan 2016, at 10:32, Andy Seaborne <[email protected]> wrote:
>
> 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
>>>>>>
>>>>>>
>>>>>> -- 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.
>>>>>>
>>>>>
>>>>
>>
>
