> On 20 Oct 2024, at 9:56 PM, Andy Seaborne <a...@apache.org> wrote:
>
>
>
> On 19/10/2024 12:43, Holger Knublauch wrote:
>> Hi Andy,
>> I don't know what the expected behaviour should be so it's hard to define a
>> test with an assertion.
>> But here is an executable example:
>
> Excellent.
>
> The simple query shows it isn't FILTER or EXISTS related.
>
> > Do you agree that it would be better if substitution would expand SELECT *
> > to how initialBinding behaves?
>
> I neither agree nor disagree at the moment. It looks OK, but there are other
> use cases to consider. InitialBindings was limiting from both a query
> optimizer point-of-view and parametrized queries for remote execution.
>
> A workaround for the current release seems to be:
>
> Query query = QueryFactory.create(....)
> query.setQueryResultStar(false);
Thanks for this workaround.
FWIW we noticed a related slight difference when a variable on the right of a
BIND was pre-bound. This used to work with initialBindings, although I think it
was illegal already and perhaps a leftover from the LET days. So I believe we
need to eliminate those legacy solutions anyway.
Can you already anticipate at which Jena version you will delete
initialBindings? Asking because it may be best for us to stick to
initialBindings and activate substitution as a flag only for a couple of
releases until we have fully identified all cases that need to be adjusted.
Thanks
Holger
>
> I haven't looked at nested SELECTs yet.
>
> > (Needless to say this impacts SHACL-SPARQL).
>
> That's a whole subject in itself.
>
> This syntax-based substitution is very similar to SEP-0007 [1] but that is
> injection into the algebra. It keeps the variables names in place (e.g.
> BOUND).
>
> Andy
>
> [1]
> https://github.com/w3c/sparql-dev/blob/main/SEP/SEP-0007/sep-0007.md
>
>
>> import java.util.List;
>> import org.apache.jena.query.Query;
>> import org.apache.jena.query.QueryExecutionDatasetBuilder;
>> import org.apache.jena.query.QueryFactory;
>> import org.apache.jena.query.ResultSet;
>> import org.apache.jena.rdf.model.Model;
>> import org.apache.jena.rdf.model.ModelFactory;
>> import org.apache.jena.sparql.core.Var;
>> import org.apache.jena.sparql.engine.binding.Binding;
>> import org.apache.jena.vocabulary.OWL;
>> import org.apache.jena.vocabulary.RDF;
>> import org.apache.jena.vocabulary.RDFS;
>> public class SelectStarSubstitutionTest {
>> public static void main(String[] args) {
>>
>> Model model = ModelFactory.createDefaultModel();
>> model.add(OWL.Thing, RDF.type, OWL.Class);
>> model.add(OWL.Nothing, RDF.type, RDFS.Class);
>> Query query = QueryFactory.create("SELECT * { ?this a ?type }");
>> ResultSet rs = QueryExecutionDatasetBuilder.create().
>> query(query).
>> model(model).
>>
>> //initialBinding(Binding.builder().add(Var.alloc("this"),
>> OWL.Thing.asNode()).build()).
>> substitution("this", OWL.Thing).
>> select();
>> List<String> vars = rs.getResultVars();
>> System.out.println(vars.size());
>> }
>> }
>> The output as shown is 1. If we use initialBinding instead of substitution,
>> the output is 2.
>> Do you agree that it would be better if substitution would expand SELECT *
>> to how initialBinding behaves?
>> One reason is that this would return 0 results if ?type is replaced with a
>> constant.
>> Another reason is that it makes the behaviour inconsistent when it returns
>> different variables depending on whether
>> a variable is pre-bound or not, e.g. when people use such SPARQL queries
>> with optional parameters.
>> (Needless to say this impacts SHACL-SPARQL).
>> Thanks
>> Holger
>>> On 17 Oct 2024, at 1:42 PM, Andy Seaborne <a...@apache.org> wrote:
>>>
>>>
>>>
>>> On 17/10/2024 11:35, Holger Knublauch wrote:
>>>> Hi all,
>>>> we are trying to switch to Jena 5 and from using setInitialBindings to
>>>> substitution.
>>>> There is a change in behaviour of SELECT *
>>>> Consider a query such as
>>>> SELECT *
>>>> WHERE
>>>> { ?this ?PATH ?value
>>>> FILTER EXISTS { ?value (rdfs:subClassOf)* ?class
>>>> FILTER ( ?class IN (rdfs:Class, rdf:Property,
>>>> sh:Shape) )
>>>> }
>>>> }
>>>> where ?this and ?PATH have initial bindings.
>>>> Using initialBindings, the result variables include ?this, but with
>>>> substitution semantics, only ?value is returned.
>>>> Does this mean that queries need to be rewritten to explicitly state
>>>> SELECT ?this ?value ... ?
>>>> Thanks,
>>>> Holger
>>>
>>> Hi Holger,
>>>
>>> Minimal, complete test case please.
>>>
>>> (Presumably ?PATH is a property not a more general path)
>>>
>>> Andy
>>>
>
