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Re: Graphs Design 6.2

From: Steve Harris <steve.harris@garlik.com>
Date: Thu, 26 Apr 2012 15:27:46 +0100
Cc: Sandro Hawke <sandro@w3.org>, public-rdf-wg WG <public-rdf-wg@w3.org>
Message-Id: <57A8FCE8-BE89-43A7-9DEA-0ABF29C2FF5B@garlik.com>
To: Richard Cyganiak <richard@cyganiak.de>
On 2012-04-25, at 21:45, Richard Cyganiak wrote:

> Hi Steve,
> 
> On 25 Apr 2012, at 19:54, Steve Harris wrote:
>>> @union is just syntactic sugar in TriG, shorthand for having to
>>> repeat all the triples in all the named graphs.
>>> 
>>> Does that change your mind about it, at all?
>> 
>> Not really.
>> 
>> The implication of that would be that if I see @union I have to disable an optimisation that's designed specifically to handle that (common) case.
> 
> Why do you need to disable the optimisation? If your store has the optimisation (union default graph), then you already know that it will automatically do what @union asks for, so you just have to load the named graphs and are done.
> 
> If your store *didn't* have a union default graph, only then it would have to do something special when it sees @union: load every triple twice, both into a named graph and into the default graph.

Either way you're screwed - see my other mail.

>> I don't see how it makes ay sense to allow a data format to specify that behaviour, it should normally be up to the query author.
> 
> @union doesn't specify behaviour. It specifies what triples are in the default graph of the serialized dataset. It doesn't dictate what happens when you load that dataset into a store.

That's not the impression I get by reading the examples. If it /doesn't/ alter the behaviour of the store then it's useless, the query engines default behaviour will just make it moot.

- Steve

-- 
Steve Harris, CTO
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Received on Thursday, 26 April 2012 14:28:26 UTC

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