Re: on divergence between textual and SPARQL definitions

Peter, is this an indirect issue of the validators definition where we do
not explicitly state that $this is prebound to the focus node?
http://w3c.github.io/data-shapes/shacl/#constraint-components-validators


On Fri, Dec 9, 2016 at 12:19 PM, Andy Seaborne <andy@apache.org> wrote:

> Peter,
>
> On 09/12/16 02:46, Peter F. Patel-Schneider wrote:
> ...
>
>> The SPARQL definition here uses the following SPARQL query
>>
>> SELECT DISTINCT $this ?value
>> WHERE {
>>   $this ex:p ?value .
>>   FILTER NOT EXISTS
>>     { $value rdf:type/rdfs:subClassOf* $class . }
>>   }
>>
>> with this pre-bound to ex:n and class pre-bound to ex:c.
>>
>> According to the SHACL document
>> evaluating this SPARQL query will produce a non-empty solution sequence,
>> namely
>>   { { (this, ex:m), (value,ex:l) } }
>> because
>>   $this ex:p ?value .
>> will produce the set of solutions
>>   { { (this, ex:n), (value,ex:m) } ,
>>     { (this, ex:m), (value,ex:l) } }
>>
>
> I don't follow this part.
>
> On just the " $this ex:p ?value ." pattern, why, when ?this=ex:n, is the
> second solution present?
>
> I think there is only one match. { { (this, ex:n), (value,ex:m) } }
> and then the overall result is zero rows.
>
>
> For both proposal-A and proposal-B used for pre-binding, that seems to be
> the case.  $this is restricted before the FILTER is applied.
>
> (NB I acknowledge that Proposal-A is not proposed for pre-binding and
> wasn't suggested as such)
>
>         Andy
>
>


-- 
Dimitris Kontokostas
Department of Computer Science, University of Leipzig & DBpedia Association
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