Re: [OWLAPI-developer] Database Backend and Triple Store support

[Matthew H. <mat...@cs...>]

Hi Chumming,

> Since axiom-centric OWL API in-memory model is more efficient than a
> corresponding triple based in-memory model. It is natural to think  
> that
> an axiom-centric database backend would be better than a triple store?

This might be a possibility, but it is difficult to say.

  Both of these solutions could be provided as OWL API backends  
though, because the OWL API doesn't commit to triples or any other  
concrete representation format or syntax.  Personally, I am sceptical  
about the use of a database for storing a TBox - even with very large  
ontologies such as SNOMED or the NCI ontology (incidentally, the  
actual ontology in the NCI TBox probably accounts for about 1/5 to 1/4  
of the size of the ontology -- the rest is annotations), the amount of  
memory required to load such ontologies isn't a vast amount  
considering the memory that modern machines have.  Also, putting a  
TBox into a database generally screws reasoning since reasoners such  
as Pellet or FaCT++ need to "see" the whole ontology anyway, so  
inevitably, it gets loaded into memory.  With regards to storing  
ABoxes in database or triple stores then I can see more sense in this  
if the ontology doesn't contain nominals and the ABox is very large.

Cheers,

Matthew


> Cheers,
>
> Chuming
>> It is possible to add a new implementations of the OWLOntology
>> interface - one could imagine that such an implementation could be
>> based on some triple store (e.g. Sesame).  In terms of in-memory
>> triple stores then I don't think this makes sense.   This is because
>> the OWL API is generally more efficient in terms of memory usage (and
>> load time) than a corresponding triple based API implementation.
>>
>> Cheers,
>>
>> Matthew
>>
>>
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