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Re: Wishlist for SPARQL 1.2: Compatible query-hints

From: Jerven Bolleman <jerven.bolleman@isb-sib.ch>
Date: Tue, 30 Jul 2013 17:10:12 +0200
Message-ID: <51F7D754.8030403@isb-sib.ch>
To: Bryan Thompson <bryan@systap.com>
CC: william greenly <william_greenly@hotmail.com>, "public-sparql-dev@w3.org" <public-sparql-dev@w3.org>, "public-rdf-dawg-comments@w3.org" <public-rdf-dawg-comments@w3.org>, Kingsley Idehen <kidehen@openlinksw.com>
Hi Bryan,

Thank you for the reply. Just to note I would be happy with a convention 
before standardization as well :)
On 30/07/13 16:25, Bryan Thompson wrote:
> A few points:
>
>   * Prefix hints alone are not sufficiently rich.  We use "virtual
>     triples" so we can influence specific joins, sub-groups,
>     sub-selects, etc.
>   * We use a namespace for hints so people can identify any bigdata
>     specific dependencies in their queries.
>   * Query hints sometimes are necessary for an application to "work".
>     This might mean having reasonable performance, but it also might
>     mean accessing a vendor specific functionality.  A very similar
>     problem arises if you have a SERVICE that interprets the graph
>     pattern as having specialized semantics.  E.g., as supporting full
>     text, geospatial search, other sorts of "extension" services.
>   * Even if you have standard hint syntax (which would be nice), the
>     semantics of the hints will not be standard and hence applications
>     will still not be portable.
>
All very good points
> One suggestion would be to introduce a marker (similar to the "#"
> character for comments) that indicates that the triple pattern is a
> query hint.  This would make it possible for the hints to be
> automatically ignored if they do not pertain to a specific platform
> (e.g., because the hints are not in an understood namespace for that
> platform).
>
> To draw an example from the link to our wiki below [1], you might use
> the "%" character to mark the triple pattern as a query hint (we do not
> currently recognize that syntax  this is just an example to indicate
> what I mean).
I would choose something like a special comment such as #hint as that 
should be backwards compatible i.e. an ignored comment to a strict 1.1 
engine.
>
> PREFIX rdf:  <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
> PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
> PREFIX foaf: <http://xmlns.com/foaf/0.1/>
>
> SELECT ?x ?o
> WHERE {
>
>    # disable join order optimizer for this group graph pattern.
> %  hint:Query hint:optimizer "None" .
>
>    ?x rdfs:label ?o .
>    ?x rdf:type foaf:Person .
> }
>
>
> Thanks,
> Bryan
> [1] http://sourceforge.net/apps/mediawiki/bigdata/index.php?title=QueryHints
>
> From: william greenly <william_greenly@hotmail.com
> <mailto:william_greenly@hotmail.com>>
> Date: Tuesday, July 30, 2013 10:15 AM
> To: "Jerven. Bolleman" <jerven.bolleman@isb-sib.ch
> <mailto:jerven.bolleman@isb-sib.ch>>, "public-sparql-dev@w3.org
> <mailto:public-sparql-dev@w3.org>" <public-sparql-dev@w3.org
> <mailto:public-sparql-dev@w3.org>>, "public-rdf-dawg-comments@w3.org
> <mailto:public-rdf-dawg-comments@w3.org>"
> <public-rdf-dawg-comments@w3.org
> <mailto:public-rdf-dawg-comments@w3.org>>, Kingsley Idehen
> <kidehen@openlinksw.com <mailto:kidehen@openlinksw.com>>, Bryan Thompson
> <bryan@systap.com <mailto:bryan@systap.com>>
> Subject: RE: Wishlist for SPARQL 1.2: Compatible query-hints, extra math
> operators
>
> Excellent - Yes! SPARQL 1.2. If we want to follow in the footsteps of
> SPARQL 1.1 we should ensure 1.2 has lots of major changes in protest
> against semantic versioning.
>
>> Date: Tue, 30 Jul 2013 16:05:27 +0200
>> From:jerven.bolleman@isb-sib.ch <mailto:jerven.bolleman@isb-sib.ch>
>> To:public-sparql-dev@w3.org <mailto:public-sparql-dev@w3.org>;
> public-rdf-dawg-comments@w3.org
> <mailto:public-rdf-dawg-comments@w3.org>; kidehen@openlinksw.com
> <mailto:kidehen@openlinksw.com>; bryan@systap.com <mailto:bryan@systap.com>
>> Subject: Wishlist for SPARQL 1.2: Compatible query-hints, extra math operators
>>
>> Dear Workgroup, All,
>>
>> Maybe not the best moment to bring this up as the ink on SPARQL 1.1 is
>> not even dry yet. But looking to the future could we start thinking
>> about SPARQL 1.2 and what could be standardized there.
>>
>> The first need I am seeing is the need to standardize query hints.
>>
>> Oracle uses extra prefix declarations for query hints [1].
>> BigData uses magic BGP's [2]
>> Virtuoso introduced a new keyword ASSUME [3]
>>
>> The BigData and Virtuoso approach introduce query incompatibilities
>> which is unfortunate. Oracle is ok in this respect as the unused
>> prefixes won't affect any strictly compatible sparql engine. I like the
>> idea that any SPARQL query will run on any store the only thing changing
>> is speed. Extra keywords or non existing BGP's break this utopia :(
>>
>> The second is an expansion of the basic math operators to include at
>> least (square)root. (square)root is very hard to implement using the
>> current SPARQL constructs yet is a very useful function. (even if not exact)
>>
>> Regards,
>> Jerven
>>
>>
>>
>> [1]
>>http://docs.oracle.com/cd/E18283_01/appdev.112/e11828/sem_jena.htm#CBBIAGAF
>> [2]http://sourceforge.net/apps/mediawiki/bigdata/index.php?title=QueryHints
>> [3]
>>http://sourceforge.net/mailarchive/forum.php?thread_name=51F67BB8.7030302%40openlinksw.com&forum_name=virtuoso-users
>>
>>
>>
>>
>> --
>> -------------------------------------------------------------------
>> Jerven BollemanJerven.Bolleman@isb-sib.ch <mailto:Jerven.Bolleman@isb-sib.ch>
>> SIB Swiss Institute of Bioinformatics Tel: +41 (0)22 379 58 85
>> CMU, rue Michel Servet 1 Fax: +41 (0)22 379 58 58
>> 1211 Geneve 4,
>> Switzerland www.isb-sib.ch - www.uniprot.org
>> Follow us athttps://twitter.com/#!/uniprot
>> -------------------------------------------------------------------
>>


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  Jerven Bolleman                        Jerven.Bolleman@isb-sib.ch
  SIB Swiss Institute of Bioinformatics  Tel: +41 (0)22 379 58 85
  CMU, rue Michel Servet 1               Fax: +41 (0)22 379 58 58
  1211 Geneve 4,
  Switzerland     www.isb-sib.ch - www.uniprot.org
  Follow us at https://twitter.com/#!/uniprot
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Received on Tuesday, 30 July 2013 15:10:57 UTC

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