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Re: Property Path Profiles

From: Andy Seaborne <andy.seaborne@talis.com>
Date: Mon, 11 Jan 2010 19:29:34 +0000
Message-ID: <4B4B7C1E.4070007@talis.com>
To: matthew.perry@oracle.com
CC: W3C SPARQL Working Group <public-rdf-dawg@w3.org>


On 11/01/2010 6:33 PM, Lee Feigenbaum wrote:
>
> Matt Perry wrote:
>> Hi,
>>
>> During the last TC, I mentioned the possibility of a Property Paths
>> profile that identifies a subset of property path queries that can be
>> expressed with SQL. Such a profile would make it easy for triple
>> stores implemented on top of relational databases to identify the set
>> of property path queries that they "natively" support. The purpose of
>> this email is to start a discussion about the possibility of property
>> path profiles.
>>
>> The grammars below show two possible fragments that we have
>> identified. The first grammar is for SQL + CONNECT BY (Oracle) and the
>> second is for PLAIN SQL.
>>
>> CONNECT BY:
>>
>> ALT -> URI | URI|ALT
>> SEQ -> URI | URI/SEQ
>> Elem -> URI | SEQ | ALT | ^URI
>> COMP -> URI | Elem* | Elem+ | Elem{n,m} | Elem?
>> TOP -> URI | COMP | ALT | SEQ | ^URI
>>
>> PLAIN SQL:
>>
>> ALT -> URI | URI|ALT
>> SEQ -> URI | URI/SEQ
>> Elem -> URI | SEQ | ALT | ^URI
>> COMP -> URI | Elem{n,m} | Elem?
>> TOP -> URI | COMP | ALT | SEQ | ^URI
>
> Are the Plain SQL set simply the set that can be expanded as a (possibly
> complicated) SPARQL 1.0 query string? (This is sort of but not exactly
> what's termed a "simple path" in the current doc.)
>
> Do other DBMSes included equivalent/similar functionality to CONNECT BY?
> I'm hesitant to go down a multi-level conformance path in the first
> place, but I'd be even more hesitant to do so if it were just in the
> context of a single DBMS.
>
> Lee

Doesn't it also depend on the RDF modelling in the SQL database as well?

There may be a precalulated tables for some cases e.g. the answers to 
rdf:type/rdfs:subClassof* (such expansion at load time is done by 
several SPARQL systems - I have prototyped this for SQL before).

Even with a direct mapping to an SQL triple table, what about WITH 
RECURSIVE?   Can't that be used?

http://www.postgresql.org/docs/8.4/static/queries-with.html

http://www.ibm.com/developerworks/data/library/techarticle/dm-0510rielau/

	Andy

>
>>
>> Thanks,
>> Matt
>>
>>
>>
>>
>
>
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Received on Monday, 11 January 2010 19:30:07 GMT

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