/**
* Compute the variable names occurring in the service expression using tree traversal, since
* these are necessary for building the SPARQL query.
*
* @return the set of variable names in the given service expression
*/
private Set<String> computeServiceVars(TupleExpr serviceExpression) {
final Set<String> res = new HashSet<String>();
serviceExpression.visit(
new AbstractQueryModelVisitor<RuntimeException>() {
@Override
public void meet(Var node) throws RuntimeException {
// take only real vars, i.e. ignore blank nodes
if (!node.hasValue() && !node.isAnonymous()) res.add(node.getName());
}
// TODO maybe stop tree traversal in nested SERVICE?
// TODO special case handling for BIND
});
return res;
}
