Re: LDOM algorithm (very early draft)

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On 02/06/2015 04:39 PM, Holger Knublauch wrote:
> 
> On 2/6/15 11:19 PM, Peter F. Patel-Schneider wrote:
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>> 
>> My question concerned how LDOM could handle recursive shapes.  I see in
>> the document:
>> 
>> Some other things that SPARQL engines need to implement: Ability to
>> execute ldom:Functions (recursive SPARQL queries), details to be
>> written up Some built-in functions, esp ldom:violatesConstraints, which
>> maps to checkNodeAgainstConstraint here.
>> 
>> It thus appears that LDOM is not based on SPARQL but is based instead
>> on an extended SPARQL.
> 
> Yes, if a SPARQL engine claims LDOM support, then it needs to implement 
> user-defined functions as well as a few built-in functions. The function 
> ldom:violatesConstraints is basically the entry point into the
> validation. If a database does not support these extensions, then it is
> still possible to use LDOM via higher-level APIs such as Jena and Sesame.
> Maybe we could define an entry function such as ldom:support() that can
> be asked against a SPARQL engine to see if it supports LDOM or not.
> 
>> The ability to handle recursive SPARQL queries may turn out to be a
>> significant change to SPARQL engines.  Further, there are not 
>> sufficient details here to determine whether the required augmentations
>> to SPARQL engines can be used to implement recursive shapes.
> 
> I thought we had discussed this already, but it will become clearer once
> we have written up the spec.

Yes, it has been discussed, but I haven't seen any indication from the
presented information that the approach can handle recursive, as opposed to
nested, shapes.

>> The document also contains wording indicating that it is not using
>> RDFS vocabulary in the way that this vocabulary is meant to be used.
>> For example, subclass determination is not done in the way specified by
>> RDFS.
> 
> Could you clarify this? I believe the interpretation of rdfs:subClassOf
> in LDOM does not contradict with RDFS.

It appears from the document that LDOM does not completely implement
subclass processing from RDFS in that it does not appear to take into
account subproperties of subclass.

> Thanks, Holger

peter

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Received on Saturday, 7 February 2015 04:10:12 UTC