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Re: Imports issue

From: Sean Bechhofer <seanb@cs.man.ac.uk>
Date: Thu, 20 Feb 2003 09:05:31 +0000 (GMT Standard Time)
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
cc: schreiber@swi.psy.uva.nl, <www-webont-wg@w3.org>
Message-ID: <Pine.WNT.4.44.0302200853560.2400-100000@potato>

On Wed, 19 Feb 2003, Peter F. Patel-Schneider wrote:

>
> From: Guus Schreiber <schreiber@swi.psy.uva.nl>
> Subject: IImports issue
> Date: Thu, 20 Feb 2003 00:26:57 +0100
>
> > I'm feeling increasingly uncomfortable about our "imports" resolution
> > (see the discussion threads cited in the agenda).
> >
> > Unless we get in the very near future clear evidence this is an
> > implementable language feature, I will have to reopen this issue and
> > propose to give imports the same informnal status as the versioning stuff.
>
> Huh?
>
> To implement imports, it suffices to modify an RDF/XML processor as
> follows:
>
>    Whenever an imports triple is found, first check to the if the object of
>    the triple has been imported already.   If not, get the document that is
>    pointed to by the object of the triple and run it through the RDF/XML
>    processor.  Then merge the result with the current graph.  Only a very
>    small amount of care is required to prevent loops.
>
> What could be easier?
>
> What is currently being argued about is how imports interacts with OWL Lite
> and OWL DL, i.e., what documents containing imports count as an OWL Lite or
> OWL DL document.
>
> > Note that responses of the type "this is a useful/necessary feature" are
> > not helpful at this point.
>
> > If we cannot show that imports  can be
> > implemented, we will not be able to go to Proposed Rec with the OWL spec
> > as it stands.
>
> This is crazy!  Who has claimed that imports is not implementable!

I would second Peter on this. Raphael and I have (almost) built a species
validator that deals with imports (in exactly the way that Peter
described). The difficulty is not in gathering the triples, but in being
clear about how imports interacts with validation.

I still have some concerns as raised in a previous message [1] about the
fact that you really have to get *all* the triples before you can be sure
of doing everything, but that is not a bar to implementation -- simply a
requirement for lots of memory.

Similarly, implementing imports as "grab all the triples and add them in"
does not preclude the use of imports for modularisation (another concern
of mine [2]). The main issue there is whether we can make the collections
of triples that are imported "self-contained" enough to allow them to be
used/processed independently through tighter restrictions on the form of
triples allowed in OWL.

Cheers,

	Sean

[1] http://lists.w3.org/Archives/Public/www-webont-wg/2003Feb/0206.html
[2] http://lists.w3.org/Archives/Public/www-webont-wg/2003Feb/0207.html

-- 
Sean Bechhofer
seanb@cs.man.ac.uk
http://www.cs.man.ac.uk/~seanb
Received on Thursday, 20 February 2003 04:06:38 GMT

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