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Re: LANG: need to CLOSE Issue 5.6 Imports as magic syntax

From: Dan Connolly <connolly@w3.org>
Date: 29 Oct 2002 12:47:53 -0600
To: Jeff Heflin <heflin@cse.lehigh.edu>
Cc: Jim Hendler <hendler@cs.umd.edu>, webont <www-webont-wg@w3.org>
Message-Id: <1035917273.24110.8003.camel@dirk>

On Tue, 2002-10-29 at 09:20, Jeff Heflin wrote:
[...]
> Therefore, I propose the following:
> 
> 1) The syntax for imports be the same as that of DAML+OIL
> 
> 2) The semantics essentially be "A imports B means if B entails P then A
> entails P."

No, entailment is a relationship between formulas; it doesn't
depend on the state of the Web.

I much prefer defining something like imports closure.

i.e. the imports closure of D is the graph you get from D
plus following all the (syntactically evident) daml:imports
links, recursively.

"the" graph here is somewhat informal; you get different
graphs depending on the state of the web; this is inherent
to the defintion of imports closure.

We can then use our existing notion of entailment
to test whether the imports closure of D1 entails D2.
At the ftf, we discussed having a separate class of
tests for this relationship between D1 and D2.


> Here A and B can be any document, not just ontologies. Also
> note that when a document does not contain an imports statement, we do
> not specify a mechanism for determining what statements from other
> documents are entailed.

It seems to me that entailment (i.e. large-owl entailment and
fast-owl entailment) is 100% specified; we leave no room
for interpretation, implementation-dependency, change-over-time,
etc.

> Thus, developers are free to implement various
> things, just as they are free to combine arbitrary unlinked documents.
> However, in such situations, they take responsibility for the
> conclusions they make.
> 
> 3) The imports triples are considered extra-logical, and any statements
> that contain owl:imports as a subject or object are undefined.

??? What do you mean by "undefined"? How should that be specified
in the ref/semantics/guide docs?

Perhaps you mean that they don't affect the imports closure of
a document (i.e. you can't expect agents to pay attention
to subproperties of imports when computing the imports closure)
then very well.

> Furthermore, any imports statements that have a resource other than the
> containing document as a subject are undefined.
> 
> I suggest that anybody who cannot live with this solution speak up now
> and clearly explain how this would break their applications. If there
> are no serious objections with it, I'd be happy to write up the details
> of this proposal.

I don't know if you consider this an objection or a clarification
question. In any case, I need to see more details (in particular:
test cases that show that imports *does not* affect large/fast
entialment, plus test cases regarding imports closure) before
I'm prepared to agree.



> 
> Jeff
> 
> [1] http://lists.w3.org/Archives/Public/www-webont-wg/2002Oct/0057.html 
> [2] http://lists.w3.org/Archives/Public/www-webont-wg/2002Oct/0141.html
> [3] http://lists.w3.org/Archives/Public/www-webont-wg/2002Oct/0060.html
> [4] http://lists.w3.org/Archives/Public/www-webont-wg/2002Oct/0150.html

-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Tuesday, 29 October 2002 13:47:37 GMT

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