- From: Steve Harris <steve.harris@garlik.com>
- Date: Wed, 14 Mar 2012 11:06:19 +0000
- To: "Polleres, Axel" <axel.polleres@siemens.com>
- Cc: Andy Seaborne <andy.seaborne@epimorphics.com>, "public-rdf-dawg@w3.org" <public-rdf-dawg@w3.org>
On 2012-03-14, at 10:45, Polleres, Axel wrote:
> (sorry, hot "send" to early)
>
>> Could you expand on "we need DISTINCT"? Is that just a technical
>> point that DISTINCT covers more or a political point about the
>> comments?
>
> For me this is definitly a technical point, since a DISTINCT-paths
> -semantics, which can be optimized/efficiently implemented, doesn't
> seem to be feasible by recognizing DISTINCT subqueries alone,
> at least not trivially...
>
> I.e., while DISTINCT() can possibly be defined in terms of a rewriting
> (which introduces fresh variables for blank nodes), I think that's neither
> elegant nor very practical for optimizations without the explicit keyword,
> whereas a syntactic element DISTINCT() gives a direct handle for
> optimizations, right?
>
> So, I think this is important *both* technically and in in order
> to address the comments.
>
>> What about the lesser case of just {*}{+} and *+ changes?
>
> I am fine with having those, but for the reasons above, I would
> feel uncomfortable going without DISTINCT().
To speak bluntly, this seems crazy!
Adding both DISTINCT and {*} {+} / * + is taking an already complex feature and making it a significant challenge to implement.
- Steve
--
Steve Harris, CTO
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Received on Wednesday, 14 March 2012 11:07:06 UTC