Re: SPARQL EXISTS variations

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 Thursday, 21 August 2025 10:09:37 UTC