RDFS & import & reasoning

[Maatari Daniel Okouya <ok...@usi.ch>]

Dear Everyone,

I'm new to RDFS and I would like to understand something that i can't  
figure out by myself.

I would like to know if RDFS reasoner support ontology import. What i  
mean is that in OWL it is clear that to import an ontology and not  
just identify  the external element via namespace, it is required to  
use the import statement. this way all the definition including  
assertion axiom of the imported ontology are available in the  
importing ontology.

However this mechanism do not exist in RDF. I suppose that it is the  
reason why, RDFS necessitate a specific native support in the tools.  
That , the tools such as jena already posses the definition of RDFS.  
My question now would be:

If i define, an ontology using RDFS in a file let say onto1 and create  
another ontology in another file onto2 that use terms defined in  
onto1. Can the jena reasoner properly reason on onto2. will it be able  
to recover information from onto1. If yes, what are the proper  
contruct in RDFS/XML to support the import. Is this behavior Jena  
specific or any reasoner can?



Many thanks

Re: RDFS & import & reasoning

[Dave Reynolds <da...@gmail.com>]

Hi,

On Wed, 2011-08-03 at 21:44 +0200, Maatari Daniel Okouya wrote: 
> Dear Everyone,
> 
> I'm new to RDFS and I would like to understand something that i can't  
> figure out by myself.
> 
> I would like to know if RDFS reasoner support ontology import. What i  
> mean is that in OWL it is clear that to import an ontology and not  
> just identify  the external element via namespace, it is required to  
> use the import statement. this way all the definition including  
> assertion axiom of the imported ontology are available in the  
> importing ontology.
> 
> However this mechanism do not exist in RDF. I suppose that it is the  
> reason why, RDFS necessitate a specific native support in the tools. 

?? Don't know what you mean by that, to reason with RDFS you need an
RDFS reasoner, nothing to do with import processing.

> That , the tools such as jena already posses the definition of RDFS.  
> My question now would be:
> 
> If i define, an ontology using RDFS in a file let say onto1 and create  
> another ontology in another file onto2 that use terms defined in  
> onto1. Can the jena reasoner properly reason on onto2. will it be able  
> to recover information from onto1. If yes, what are the proper  
> contruct in RDFS/XML to support the import. Is this behavior Jena  
> specific or any reasoner can?

There are (at least) two plausible approaches here:

(1) Use owl:imports to explicitly import the ontologies you are
interested in. RDFS is true subset of OWL Full so there is no problem
using owl:imports and no other OWL constructs in you instance data. That
way you can use Jena's OntModel implementation to do the import
processing for you but can define it to just use the RDFS reasoner.

(2) Adopt a convention that any mention of an ontology term should cause
your processor to dereference that URI and add whatever comes back as an
implicit import and then reason over the recursive closure of those
imports. Some tools work this way. Jena allows you to write such tools
on top but doesn't implement it natively (it is not part of the RDF/RDFS
specs and can be very expensive and fragile).

With (1) you don't need any code other than configuring the Jena
OntModel but onto1 has to explicitly import onto2.

With (2) you are going beyond the specs, though in a reasonable way, and
would need to write your own additional processing layer to configure
the RDFS resasoner.

Dave