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

From: Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>
Date: Tue, 12 Feb 2008 18:09:19 +0000
Message-Id: <42592BB9-D7E3-4BC8-8EE5-ED099AA4819F@comlab.ox.ac.uk>
Cc: Jim Hendler <hendler@cs.rpi.edu>, "Web Ontology Language ((OWL)) Working Group WG" <public-owl-wg@w3.org>
To: Jeremy Carroll <jjc@hpl.hp.com>

I share Jeremy's desire to maintain a significant degree of rigour  
w.r.t. OWL Full; in fact I would say the same for all species/ 
fragments/conformance-levels. Moreover, from what Jim says in emails  
such as [1] it would seem that he has no objection to this and  
perhaps even believes it to be mandatory. Instead, what he seems to  
be asking for (in [1] at least) is a more human readable explanation  
for those who find model theories difficult to understand. I don't  
see any problem with that -- in fact we already have a commitment to  
producing such documents and even a UFDTF busily engaged in their  
development. So, if we were to agree to produce a "delta to OWL-1.0- 
Full" as outlined by Michael in [2] plus suitable documentation for  
the MT-challenged, would this satisfy everyone's requirements?

Ian

[1] http://lists.w3.org/Archives/Public/public-owl-wg/2008Feb/0069.html
[2] http://lists.w3.org/Archives/Public/public-owl-wg/2008Feb/0068.html


On 11 Feb 2008, at 09:05, Jeremy Carroll wrote:

>
>
> 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
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Received on Tuesday, 12 February 2008 18:09:42 GMT

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