Re: SPARQL EXISTS variations

I believe that there is a problem with SERVICE constructs - you can't send the 
binding sets to the remote service as a VALUES construct because you can't 
send blank nodes correctly.

peter


On 8/24/25 2:54 PM, Olaf Hartig wrote:
> Hi EXISTS TF members,
> 
> I have updated my document after last Friday's discussion.
> 
> https://gist.github.com/hartig/3fffc7a02f3e0411158298e313b4c9c2
> 
> Most importantly, I have added a detailed discussion of all cases
> possible for the pattern within an EXISTS expression---see the section
> called "Why is a similar change not needed for the other cases?"
> 
> I have also tried to add the document into the repo [1], but somehow
> the CI run of the corresponding PR failed. Until this is fixed, the
> link above is the most recent version of the document.
> 
> -Olaf
> 
> [1] https://github.com/w3c/sparql-query/pull/270
> 
> 
> On Fri, 2025-08-22 at 11:03 +0000, Olaf Hartig wrote:
>> Hi,
>>
>> As the different variations were mentioned only informally in Peter's
>> email, I wanted to convince myself that we can
>> also define them formally in the spec. For the DEEP INJECTION
>> variations it was not immediately clear to me how this
>> could be done; especially not for the OVERALL-variant of DEEP
>> INJECTION.
>>
>> I found a way to do it (based on an idea that Andy mentioned during
>> the last TF meeting), and wrote a short document to
>> describe the exact changes that are needed:
>>
>> https://gist.github.com/hartig/3fffc7a02f3e0411158298e313b4c9c2
>>
>>
>> Best,
>> Olaf
>>
>>
>> On Thu, 2025-08-21 at 10:09 +0000, Olaf Hartig wrote:
>>> On Thu, 2025-08-21 at 03:17 +0200, James Anderson wrote:
>>>> On 20. Aug 2025, at 22:30, Andy Seaborne <andy@apache.org> wrote:
>>>>> On 16/08/2025 15:45, Peter F. Patel-Schneider wrote:
>>>>>> There was again discussion in the SPARQL EXISTS task force on
>>>>>> different solutions to the SPARQL EXISTS
>>>>>> problems.
>>>>>> The solutions amount to, roughly:
>>>>>> Simple LEFTJOIN, where no bindings from outside the EXISTS
>>>>>> affect the pattern inside.
>>>>>
>>>>> SEMIJOIN?
>>>>
>>>> is it not the case that, where no variable from the solution is
>>>> free in the exists pattern, that pattern reduces to
>>>> a
>>>> boolean constant value which depends only on the state of the
>>>> target graph?
>>>
>>> What do you mean with a variable being "free in the exists
>>> pattern"?
>>>
>>> I agree with Andy, it is a SEMIJOIN.
>>>
>>> @Peter, thanks for this great summary! I agree with your believe
>>> that ONCE versus OVERALL is relevant only for DEEP
>>> INJECTION.
>>>
>>> -Olaf
>>>
>>>
>>>>>
>>>>>> Values injection at the beginning of the pattern (SHALLOW
>>>>>> INJECTION).
>>>>>> Values injection inside the pattern (DEEP INJECTION), with
>>>>>> two variations
>>>>>> values projected out in sub-SELECTs are not affected
>>>>>> (PROJECTION) and
>>>>>> values projected out in sub-SELECTs are affected.
>>>>>
>>>>>
>>>>>
>>>>
>>>> ---
>>>> james anderson | james@dydra.com |
>>>> https://dydra.com/
>>>>
>>>>
>>>>
>>>
>>
>

Received on Monday, 25 August 2025 21:00:10 UTC