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Re: SPARQL vnext new feature? cascadedQueries

From: Steve Harris <swh@ecs.soton.ac.uk>
Date: Sun, 4 Nov 2007 13:29:26 +0000
Cc: public-sparql-dev@w3.org
Message-Id: <876C5512-5A53-4727-94F1-7A387D7A2D3F@ecs.soton.ac.uk>
To: Alan Ruttenberg <alanruttenberg@gmail.com>

Not all subqueries have an equivalent, at least not in SQL.

- Steve

On 4 Nov 2007, at 13:05, Alan Ruttenberg wrote:

> Is there a reason one would like to do a local subquery? Isn't it  
> equivalent to something that you could write at top level with about  
> the same number of characters?
>
> -Alan
>
> On Nov 4, 2007, at 7:55 AM, Steve Harris wrote:
>
>> Well, that would be the obvious syntax for a local sub-query too.
>>
>> - Steve
>>
>> On 4 Nov 2007, at 12:48, Alan Ruttenberg wrote:
>>
>>> Although I intended that the specification of this was that it was  
>>> only legal for an endpoint, as that's what makes it easy. I'm not  
>>> sure it's a useful construct otherwise, as you don't need it  
>>> nested in the FROM if you have to download the file.
>>> -Alan
>>>
>>>
>>> On Nov 4, 2007, at 7:38 AM, Alan Ruttenberg wrote:
>>>
>>>> Good point. Perhaps FROM ENDPOINT.
>>>>
>>>> -Alan
>>>>
>>>> On Nov 4, 2007, at 7:35 AM, Steve Harris wrote:
>>>>
>>>>> On 4 Nov 2007, at 04:09, Alan Ruttenberg wrote:
>>>>>
>>>>>> This is a particularly easy one, since it adds no new  
>>>>>> expressivity. The form
>>>>>> below can be syntactically transformed into SPARQL as specified  
>>>>>> now by way
>>>>>> of using the SPARQL protocol for the construct in the FROM.
>>>>>> Since this is the only reasonable way we have to do federation  
>>>>>> now, within
>>>>>> spec, it's more like adding friendly syntactic sugar.
>>>>>
>>>>> As far as I can tell there's no way to tell that <http://example.com/sparql? 
>>>>> > is a SPARQL endpoint, rather that a graph served by a CGI  
>>>>> script with no arguments.
>>>>>
>>>>> - Steve
>>>>>
>>>>>> On 11/3/07, Dan Connolly <connolly@w3.org> wrote:
>>>>>>>
>>>>>>> Alan Ruttenberg wrote:
>>>>>>>>
>>>>>>>> SELECT ?a ?b
>>>>>>>> FROM ( CONSTRUCT { ?d <b> ?b }
>>>>>>>>                        FROM < http://example.com/sparql?>
>>>>>>>>                      WHERE { ?b <b> ?d } )
>>>>>>>> WHERE { ?a <b> ?b }
>>>>>>>
>>>>>>>
>>>>>>> Yes... the Data Access WG considered this sort of thing briefly;
>>>>>>> we didn't see any particular reason not to do it but we...
>>>>>>>
>>>>>>> RESOLVED 2005-01-20: to postpone cascadedQueries; while  
>>>>>>> federation use
>>>>>>> cases are interesting, the designs don't seem mature and the  
>>>>>>> use cases
>>>>>>> are not urgent; with KendallC abstaining.
>>>>>>> http://www.w3.org/2001/sw/DataAccess/issues#cascadedQueries
>>>>>>>
>>>>>>> I'm happy to see people playing around with it; I hope the
>>>>>>> designs get mature soonish.
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> Dan Connolly, W3C http://www.w3.org/People/Connolly/
>>>>>>>
>>>>>>>
>>>>>
>>>>
>>>
>>
>
Received on Sunday, 4 November 2007 13:30:00 GMT

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