How to remove consistently a triple pattern given a SPARQL query?

[Carlo . Allocca]

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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