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Re: OWL Full proposal (sort of) - addressing my Action

From: Jeremy Carroll <jjc@hpl.hp.com>
Date: Mon, 11 Feb 2008 09:05:44 +0000
Message-ID: <47B00FE8.40904@hpl.hp.com>
To: Jim Hendler <hendler@cs.rpi.edu>
CC: "Web Ontology Language ((OWL)) Working Group WG" <public-owl-wg@w3.org>


I found Peter's clarification of the semantic options helpful; perhaps 
in allowing me to understand why I was uncomfortable with Jim's proposal.

Jim seems to be suggesting something inbetween Peter's "D/ Informal" and 
his "C/ Operational".
I fear we would find a long term loss in interoperability, for a short 
term gain in ease of reaching a design.

I note that any of Peter's A/ Model theory E/ Transformational or F/ 
Axiomatic can give the same level of rigour and, since we start with 
model theoretic approaches we may as well continue with them, if we want 
this level of rigour.

Jim appears to not want that.

===

I do want to maintain significant degree of rigour with the definition 
of OWL Full for a variety of reasons.

1) Architectural

My understanding of the Semantic Web is that the semantics is attached 
to the RDF graph, and different layers can *add* additional semantics to 
a graph by means of providing semantic extensions (and/or definitions of 
classes and properties in terms of ontology languages such as RDFS and OWL).
Since these semantics are additions within a strict monotonic paradigm, 
a certain degree of interoperation is provided.

There are a variety of errors in the history of RDF prior to the 
introduction of the RDF Semantics (e.g. containers and reification), 
where an informal and partially operational semantics results in systems 
that do not have such well behaved semantics and have unpredictable 
behaviour.

So the model theoretic semantics provides a discipline against error.

2) Minimize change

I personally see OWL 1.1 as a small change on OWL 1.0. The two key 
changes I believe are QCRs and subproperty chains.

I am less than happy with almost any change over and above these, other 
than minor corrections.

3) Product positioning

I don't see HP's OWL Full offering as a "scruff's only" deal (in the old 
AI scruffs v neats debate).
I see the choice of whether to use OWL (for both Full or DL) in a 
scruffy or neat fashion as an end-user decision.
The choice of Full or DL is primarily a choice about expressivity vs 
computability guarantees.

In typical OWL Full usage you get to use language features that you 
want, including ones that are not permitted in DL. You use these in the 
fashion that you want (whether neat or scruff). Then maybe an 
off-the-shelf reasoner and reasoner configuration gives you the 
trade-off you want between sufficient entailmenets vs speed - if not, 
you might need to customize your reasoning by selecting say, some rules 
out of a larger set of correct rules that cause a computational explosion.

I fear that only having an informal, operational semantics for OWL Full 
would result in OWL Full being narrowed to only certain informal and 
less than precise work.

Jeremy
Received on Monday, 11 February 2008 10:10:22 GMT

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