Re: what is LDOM? (was Re: example of recursive shapes)

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On 02/11/2015 03:45 PM, Holger Knublauch wrote:
> On 2/12/2015 1:23, Peter F. Patel-Schneider wrote:
>> - From your example below it appears that LDOM depends on an extended
>> SPARQL engine.   Of course, if you utilize a procedural extension to
>> SPARQL then you can do anything computable.
> 
> Yes correct. That's how recursion is supported. Note that this does not 
> require a fundamental change to SPARQL engines.

I disagree.  Requiring this kind of procedural extension is making a
fundamental change to SPARQL engines.

> SPARQL functions are an official extension point of the SPARQL spec, and
> all SPARQL databases that I know have added their own functions.

Sure, but so what?  LDOM is requiring a particular extension, and one that
may be difficult to implement efficiently.  The LDOM procedural extension
looks to me to be of a completely different kind than the what I take to be
normal little filter functions in the SPARQL documentation.

> If a database claims LDOM support then it needs to have some engine
> algorithm implemented anyway.

Well, in a pure SPARQL approach all that is needed is a translation engine,
and any SPARQL engine can then be used unmodified.

> Wrapping this algorithm into a SPARQL function shouldn't be all too
> difficult. Databases that do not natively support LDOM can be used via an
> outside control API such as Jena ARQ (we did something similar in the
> open source SPIN API - basically works on all databases with a Jena or
> Sesame bridge).

Really?  If SPIN can be implemented against an unmodified triple store then
that seems to be the way to go with LDOM too.

> Also note that AllegroGraph already supports recursively called SPIN
> functions that spawn off a new SPARQL query as part of another SPARQL
> query.

Does AllegroGraph also check to make sure that it is not in an infinite loop
when it is doing this?

> Holger

peter

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Received on Thursday, 12 February 2015 00:35:20 UTC