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Re: Some issues around RDF Collections and containers

From: Jos De_Roo <jos.deroo@agfa.com>
Date: Thu, 29 Jul 2004 00:30:51 +0200
To: "Dan Connolly <connolly" <connolly@w3.org>
Cc: RDF Data Access Working Group <public-rdf-dawg@w3.org>, Steve Harris <S.W.Harris@ecs.soton.ac.uk>
Message-ID: <OFEDDC2DC3.E1ED211B-ONC1256EDF.007AEC97-C1256EDF.007BA4E2@agfa.com>

DanC wrote:
> On Wed, 2004-07-28 at 10:10, Steve Harris wrote:
>> On Wed, Jul 28, 2004 at 09:49:41AM -0500, Dan Connolly wrote:
>>> On Wed, 2004-07-28 at 09:40, Steve Harris wrote:
>>>> I agree with these points wholeheartedly, but I have concern over the
>>>> difficulty and scalability issues of implementing anything to handle 
RDF
>>>> collections. Are there any large-ish RDF stores that handle these
>>>> intelligently or as a special case?
>>>
>>> cwm has a list:in built-in; i.e. it supports queries over
>>> a virtual graph that has list:in triples inferred.
>>> It's no speed daemon, though.
>>
>> This is the kind of solution I was worried about, a list of lenght N 
needs
>> N*(N+1) / 2 inferred triples,
>
> Only if you're forward-chaining. Euler would only infer the ones it
> needs, I think.

Yes, but for instance asking for all list:in solutions and their
proofs we get memory trouble with lists above 80 items, at least
while using recursive rules such as
{?L rdf:first ?X} => {?X list:in ?L}.
{?L rdf:rest ?B. ?X list:in ?B} => {?X list:in ?L}.


> Anyway... I'm not arguing strongly in favor of adding special support
> for collections. I just think it merits a place in our issues list.
> Folks who wonder "why doesn't the new-fangled DAWG-BARKING-QL from W3C
> support collections explicitly?" should get an explicit answer if
> they go poring thru the WG's records.

agreed

>>  which quickly becomes unmanageable, eg.
>> MusicBrainz has containers with several thousand members. Admittedly 
thier
>> not collections, so the problem is not as bad, but its a reasonable
>> thing to want to store in a collection.
>>
>> - Steve
> --
> Dan Connolly, W3C http://www.w3.org/People/Connolly/

-- 
Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/
Received on Wednesday, 28 July 2004 18:31:47 GMT

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