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Re: summary on options for JP-4 Comment about the semantics of property paths

From: Gregory Williams <greg@evilfunhouse.com>
Date: Sat, 11 Feb 2012 12:31:55 -0500
Cc: Lee Feigenbaum <lee@thefigtrees.net>, "SPARQL Working Group" <public-rdf-dawg@w3.org>
Message-Id: <FD2CC14C-2E4E-4DEE-BB0A-FDBDC1497C48@evilfunhouse.com>
To: Axel Polleres <axel.polleres@deri.org>
On Feb 11, 2012, at 8:26 AM, Axel Polleres wrote:

> I see some merits for option 2, particularly, because I am unclear about how optimizations can be defined in general
> for DISTINCT at arbitrary places, whereas it seems to be clear for DISTINCT around path expressions.
> So, if we know that now, why not fix it now?

Have we settled that wrapping a property path pattern in a distinct subquery satisfy's Jorge's desired existential semantics? We've provided reasons for why we think the counting semantics are important to have, and it seems as if they can be turned into the existential semantics with subqueries. This seems very much like the limit-per-resource use case to me; I'm not thrilled by the syntax required to do it, but it's possible now, and systems for which performance is critical can optimize for this case. Further, systems can experiment with deciding on how best to implement the existential semantics directly into the syntax, choosing between the many options that Andy lays out in his email, and that would provide important data for some future WG to consider.

Received on Saturday, 11 February 2012 17:32:22 UTC

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