Re: on divergence between textual and SPARQL definitions

Appendix A says:

"""
Pre-binding a variable with a value means that the SPARQL processor 
needs to evaluate all occurrences of variables with that same name 
(including occurrences in inner targets and nested SELECT queries) so 
that they have the provided value. In other words, whenever a SPARQL 
processor evaluates a pre-bound variable, it must use the given value.
"""

While the wording may not be ideal, as already noted in ISSUE-68, I read 
"they have the provided value".  The provided value is "(this, ex:n)".

So the core comment here is ISSUE-68?

     Andy

On 09/12/16 16:09, Peter F. Patel-Schneider wrote:
> Remember that the definition of pre-binding is as in the SHACL document,
> Appendix A.  The definition involves evaluation of SPARQL variables, which
> does not happen when matching BGPs.
>
> peter
>
> On 12/09/2016 02:19 AM, Andy Seaborne 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
>>

Received on Friday, 9 December 2016 17:31:12 UTC