Re: SPARQL EXISTS variations

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 Friday, 22 August 2025 11:03:26 UTC