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Re: Moving forward

From: Pat Hayes <phayes@ai.uwf.edu>
Date: Sun, 17 Mar 2002 12:38:08 -0800
Message-Id: <p0510141fb8baaba4e4e2@[]>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>, Jonathan Borden <jonathan@openhealth.org>
Cc: www-webont-wg@w3.org
>I'm not sure what you mean by ``damage''. 
>One way to go would be to
>1/ ask for ``unasserted'' stuff in RDF
>2/ place restrictions on the form of the DAML+OIL constructs
>This *might* result in a viable solution, depending on how much of a change
>is made to RDF.  The change to DAML+OIL here would be
>1/ the syntax
>2/ the model theory

I am confident that this will be a viable solution. Existing code 
does this, in effect, and seems to work reliably, and there is a 
clear strategy for providing a coherent semantics. I do not even 
think that it will require significant changes to DAML+OIL; the only 
extra requirement is that the daml:list triples be unasserted in RDF. 
It has some risks, the chief of which is that legacy RDF code which 
does not respect the 'unasserted' distinction might produce OWL 
inconsistencies. I think this is at worst an interim problem which 
will go away by itself, but we should consider it carefully.

>Another way to go would be to
>1/ use a syntax extension
>This *would* result in a viable solution.
>The change to DAML+OIL here would be
>1/ the syntax
>2/ the model theory

I agree that this would be technically viable, but it will mean that 
OWL will not be processable by RDF engines. Unless, that is, it is 
interpreted as a variation on the first way to go, in which the 
'syntax extension ' is *implemented* in unasserted RDF. The 
distinction between these 'ways to go' seems to me to be more a 
matter of aesthetic attitude than of technical content.

>A third way to go would be to
>1/ give up on a theory of classes
>This *would* result in a viable solution.  The change to DAML+OIL would be
>very small, formally, but, informally
>2/ the role of classes would change

Recent email discussions have made it clear that I would prefer that 
the semantic role of classes should be much less than Peter 
apparently would like it to be. This is an aesthetic/formal 
disagreement about the best semantic style, and isn't the kind of 
debate that it would be constructive to try to resolve in committee 
mode. I also think the world is big enough for both ways of thinking 
to coexist.

>A fourth way to go would be to
>1/ use a different semantic relationship for inference

I do not understand what this means, and request clarification. 
Entailment is pretty much established by a semantics, seems to me: A 
entails B if every model of A is also a model of B. That doesn't 
leave much flexibility for different semantic relationships for 

>This *might* result in a viable solution.  The change to DAML+OIL would be
>1/ how information is extracted from DAML+OIL KBs
>There are other ways to go that I can imagine, and probably others that I
>haven't considered.
>Which of the above qualifies as the least ``damage''?  This depends almost
>entirely on your view of what is important.

Amen to that.


>PS:  ``*would*'' above indicates that I am quite sure that a reasonable
>solution exists.  ``*might*'' above indicates that I am not convinced that
>a reasonable solution exists.
>From: "Jonathan Borden" <jonathan@openhealth.org>
>Subject: Re: Moving forward
>Date: Thu, 14 Mar 2002 17:54:43 -0500
>>  Peter F. Patel-Schneider wrote:
>>  > From: "Jonathan Borden" <jonathan@openhealth.org>
>>  > Subject: Moving forward
>>  > Date: Thu, 14 Mar 2002 16:30:11 -0500
>>  >
>>  > > It is really hard for me to believe that these semantic/layering
>>  problems
>>  > > are not solvable.
>>  >
>>  > I think that there are several examples that show that they are solvable.
>>  >
>>  > It is just that something has to be given up.  There are several of these
>>  > somethings, and there are different opinions on which one should go.
>>  >
>>  Suppose we wish to do minimal damage to DAML+OIL, e.g. use RDF but given the
>>  fact that RDF is currently being revised by RDFCore, and given the
>>  assumption that OWL will be a good customer of RDF, we have some ability to
>>  request clarifications/perhaps changes.
>  >
>>  What needs to be given up under these circumstances?
>>  Jonathan

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Received on Monday, 18 March 2002 15:05:39 UTC

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