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Re: allow implicitly unbound variables in SPARQL results?

From: Jeen Broekstra <jeen@aduna.biz>
Date: Wed, 26 Oct 2005 18:27:03 +0200
Message-ID: <435FAE57.20204@aduna.biz>
To: kendall@monkeyfist.com
CC: Dan Connolly <connolly@w3.org>, RDF Data Access Working Group <public-rdf-dawg@w3.org>

Kendall Clark wrote:
> On 16:54, Wed 26 Oct 05, Jeen Broekstra wrote:
> 
> 
>> FWIW I do not think the current design to make *excessive* use of 
>> bandwidth, except in corner cases. YMMV.
> 
> 
> Well, FWIW, that corner case is the commentor's *common* case; that 
> is, the primary of SPARQL and the results format involves 
> (necessarily) lots and lots and lots of unbounds, because the queries
>  involve OPTIONALs and UNIONS (however they're spelled, I can't 
> recall).

Yes, you are right, I should not have put it that way. I only meant that
for many use cases/queries (in which optionals and unions are not, or
sparingly) used, the bandwidth use is just fine with the current design,
and for many use cases, the ease/speed of processing is a major issue.

> That's precisely the problem that led to the unusual step of thinking
>  we could save some bytes and still have an easily human readable 
> format, keeping it in XML.
> 
> I don't believe the change to <binding/> makes processing that much 
> more difficult.

To clarify: I think my major concern (with both stripping and
collapsing, though mostly with collapsing) is not so much that it is
more difficult but that it is more costly in terms of processor
performance. Note that Ron's tests only give performance figures for the
case where you actually _have_ a significant size reduction (because it
contains a lot of unbounds).

I'd like to see some figures on how comparative processor performance is
for result sets that contain no unbounds (I'll see if I can come up with
some figures on this myself tomorrow, or perhaps Ron will do this,
you/Bijan mentioned he'd do some extra tests). That would give us a more
complete picture of the consequences of either design.

>> If, for purposes of minimizing the result set size in bytes, we 
>> offer a binary format with the reduction in size and processing 
>> time mentioned above, I think that would address his concern, 
>> although of course such a format is can not be processed with XSLT.
>>  The other option of using GZIP compression is still a viable 
>> alternative as well, IMHO.
> 
> I am only guessing here, and Bijan mentioned that Ron will be doing 
> some further tests, but I'd be really surprised if our organization 
> got behind a binary format. But, again, that's just a guess, not a 
> position.

I can very well imagine that it is simply not a good idea to introduce
this extra format into the WG at this stage of the game. I am happy to
invest time into it though if other people think it's worthwile.

*shrug* we need to document it for Sesame users anyway ;)

Jeen
Received on Wednesday, 26 October 2005 16:28:30 GMT

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