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Re: SPARQL Federation Extensions draft

From: Steve Harris <steve.harris@garlik.com>
Date: Mon, 29 Mar 2010 16:13:19 +0100
Cc: Eric Prud'hommeaux <eric@w3.org>, public-rdf-dawg@w3.org
Message-Id: <82BD2606-A50F-469B-8B51-5D71E2B90A42@garlik.com>
To: Andy Seaborne <andy.seaborne@talis.com>
+1

- Steve

On 29 Mar 2010, at 15:54, Andy Seaborne wrote:

> Eric,
>
> This is great - I think we ought to include something in SPARQL 1.1  
> even if it's just the most basic SERVICE form because of time.  It  
> it the semantic *web* ....
>
> 	Andy
>
> On 27/03/2010 3:36 AM, Eric Prud'hommeaux wrote:
>> http://www.w3.org/2009/sparql/docs/fed/service
>>
>> take a look, help out, ...
>> --
>> -ericP
>
>
> Specific comments:
> ** SERVICE
>
> "4.1 Definition of SERVICE"
> http://www.w3.org/2009/sparql/docs/fed/service#sparqlDefinition
>
> [[
> The evaluation of service uses the SPARQL algebra union operator.
> ]]
>
> Elements of a group are usually join'ed together, not union'ed.
>
> Algebra example:
>
> Service(?s :p2 ?v2)
> ==>
> Service(<srvc> BGP(?s :p2 ?v2))
>
> "with a query Q and no default or named graphs."
>
> I think that means no FROM or FROM NAMED - correct?
>
>
> ** BINDINGS
>
> This area is less clear to me - it's very useful to have something  
> here but I'm not quite sure this is the right mechanism.
>
> It's another form of assignment.
>
> Is it the same as (the excessively verbose):
>
> {
> SELECT ("Alice" AS ?given)
>       ("Anderson" AS ?family)
>       (?mbox AS <mailto:alice@example.com>)
> } UNION {
> SELECT ("Bob" AS ?given)
>       ("Robertson" AS ?family)
>       (?mbox AS <mailto:eve@example.com>)
> } UION { ... }
>
>
> Probably better not to allow bNodes to be passed over the network.
>
> Suggest s/UNBOUND/_/ or something a liitle less heavy. "-"
> The definition of BINDING has UNDEF
>
>
> * BINDING and Update:
> This seems to overlap with INSERT DATA etc
> It is unrelated to federated query.
>
> The substutute operator might help in the definition:
> http://www.w3.org/2009/sparql/docs/query-1.1/rq25.xml#defn_substitute
>
> Result are then a union of substitute for each binding row.  This is  
> similar to the bind-join proposed by the IBM Garlic project.  It  
> allows for the bINDINGs to be streamed in parallel with results  
> coming back.
>
> (this way the results of sending one BINDING at a time and sending  
> all BINDINGS at once are the same).
>
> ** MIME Type
>
> Doesn't the query often go in ?query= which isn't MIME typed.
>
> 	Andy
>

-- 
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Received on Monday, 29 March 2010 15:13:50 GMT

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