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Re: [RIFRAF] ho to proceed? Part I: Ontologization

From: Axel Polleres <axel.polleres@urjc.es>
Date: Wed, 24 Jan 2007 11:38:03 +0100
Message-ID: <45B7370B.5050805@urjc.es>
To: Leora Morgenstern <leora@steam.Stanford.EDU>, Sandro Hawke <sandro@w3.org>, W3C RIF WG <public-rif-wg@w3.org>
CC: public-rif-wg-request@w3.org

Leora Morgenstern wrote:
> I agree that to a certain extent the construction of the RIFRAF ontology 
> depends on finalizing the core.
> I think that an equally important prerequisite --- and one that we ought 
> to be doing now ---- is going through the list of RIFRAF discriminators 
>  and seeing if we can clear it up and flesh it out as much as possible.

I see the discriminators more as a way for people to articulate 
"features", maybe we should collect/stabilize the issues that we  have 
collected so far (for a summary see the other mail:
) and focus to start with a small ontology bottom-up now.

> Let me give two examples of the sort of clean-up/fleshing-out that I 
> believe is necessary.
> (1) In December, Harold Boley and I discussed some of the discriminators 
> in Sections 1 and 2  of the RAF document, Syntactic and 
> Syntactic-Entailing-Semantic Discriminators. It appeared from our 
> discussion that the distinction between these categories was not always 
> clear, and that perhaps these categories should be re-organized or 
> restructured.  (Harold, please correct me if I am incorrect.)
> In addition, it was not clear why certain syntactic features, but not 
> others, were called out in the RAF document. For example,  why (Section 
> 1.3) are Monotonic Lloyd-Topor Extensions specifically mentioned, as 
> opposed to other types of syntactic sugars?

Let me reformulate what I wanted to propose in the original mail:

  I did a start on a straw core ontologization. What I'd need is people 
to comment on the concepts and properties there, and tell me whther they 
can formalize their discriminators with it/tell me whther this is a 
valid starting point.

  I am sure that only a small part of the discrinminators can be 
coevered so far, but, as we get going we could get this forward in 
mutual feedback iterations. (A timeplan of periodic iterations wouldn't 
be too bad...)

  This is certainly only one approach, but the one I suggest to get going.

> (2) Section 5,  Discriminators for Event-Condition-Action (ECA) Rules. 
> The discriminators listed here may not include all those that are of 
> interest, and may not necessarily structure them in the best way. For 
> example, the list for 5.2.7, "Which type of event specification is used 
> in the language?" lists as the set of possible choices algebraic, linear 
> temporal logic, event calculus, and other.  Linear temporal logic is an 
> entirely different animal from the event calculus. A better structure 
> might compare linear temporal logic with languages that have explicit 
> notions of action and causation; this class of languages include 
> situation calculus, fluent calculus, and event calculus, among many 
> others. As another example, it may be useful to distinguish between 
> languages that explictly mention time points and/or intervals from those 
> that don't. This important concept, which one would expect to find in an 
> ontology of ECA languages (and indeed, in an ontology of time), is not 
> implicit in this set of discriminators.

I agree that we don't yet have a clear picture of what "event" and 
"action" etc. mean, i.e. what makes an event different from a condition, 
is on a subclass of the other, etc. I would see this as the next 
iteration step and see first how many discriminators we can cover with a 
small bunch of concepts...

> What all of this serves to underscore is that our job in ontologizing 
> the RIFRAF is not merely to decide how to structure the discriminators 
> that exist, but to try to collect as many possibly relevant 
> discriminators as we can. How we proceed in this enterprise is something 
> that we ought to discuss.

My thought on how to structure it was really on top of a CORE 
ontologization which we carefully extend.

I think these two things should really be kept separate:

1) I "core ontology" of terms used to express features of rules, 
rulesets, languages and systems.

2) Formalizations of the "discriminators" by means of these features.

Opinions, comments welcome...so, if you could have a look on the straw 
owl file I posted, we could improve it.

Sandro, can we use some W3c hosted server for subversioning or CVS for 
this? (would make sense in my opinion), if somebody has better 
experience in other tools than protege/CVS for collaboratively doing OWL 
... let me know!)


> *Axel Polleres <axel.polleres@urjc.es>*
> Sent by: public-rif-wg-request@w3.org
> 01/22/2007 07:42 PM
> Please respond to
> axel
> To
> 	W3C RIF WG <public-rif-wg@w3.org>
> cc
> Subject
> 	Re: [RIFRAF] ho to proceed? Part I: Ontologization
>  > 1) First, I will try to get something towards ontologization out of the
>  > whole core discussion, and raise some open questions there.
> We agreed that several people take over parts of the ontologization
> according to the sections of the questionnaire [3].
>   Supposedly, an overall ontology on what is a rule, condition, head,
> body, etc. would be a starting point for axiomatizing the
> discruiminators mentioned there.
> Thus, for giving it a start, I concentrated to modeling conditions and
> what is currently in the core properly for the moment.
>   I picked up a rudimentary attempt by Sandro [1] and started to
> additionally "OWLify" what I found in the last core version [2].
> Find the result as an attachment.
> If you think this approach makes sense, we could maybe further develop
> this jointly using subversioning or similar versioning software...
> Just to demonstrate why I think this is a valid starting point for
> defining axioms concerning discriminators in the current RIFRAF,
> and in which direction this could go let's look at the following
> question/discriminator from [3]:
> "1.2 Predicate Variables Permitted vs. Not Permitted
> Does your language allow predicate variables? [...]"
> This could be "axiomatized" somewhat as follows using the basic
> ontology started now by stating (I use some F-Logic-style syntax here,
> just to get to the point, hope it is readable enough):
> =======================================================================
> % Axiomatizing 1.2 in the rifraf ontology:
> % PredVarNotPermitted is a subclass of Language
> predVarNotPermitted::Language.
> % Define an  auxiliary predicate to "collect" recursively
> % all "subConditions":
> forall C, C1. C[hasCondition -> C1] implies C[hasSubCondition -> C1]
> forall C. C[hasCondition -> C1[hasSubCondition -> C2] implies
>             C[hasSubCondition -> C2]
> % Finally the rule which disallows variales for the
> % predVarNotPermitted languages:
> forall L, R,C,F.
> ( L:predVarNotPermitted and
>    R[hasRecCondition->C:ComplexTerm[hasFunctor->F:Variable]]
> )
> implies
> neg R[expressibleIn->L]
> =======================================================================
>   Main open issues are:
> a) Well, this probably looks a lot like Sandro's attempts to make an
> abstract syntax notation which is not surprising.
> b) I came to some limits very quickly, e.g.
>    How do I express that a parameter has at least one position or functor
>    describing the argument-name. This can be done in OWL, but not in
>    protege (without adding a new class). Likewise, I am unsure whether
>    the 1.2 axiomatization above can be encoded in OWL properly.
> c) Is this exercise useful or shall we wait until we have the core
>     fixed before continuing?
>     For instance: When we go further towards e.g. events, one has to ask
>     him/herself for instance whether events are a subclass of "condition"
>     or something different? How can I axiomatize in an extensible way
>     that Core rule has no events in its body, etc.
>     It seems to me that for expressing this, I need integrity constraints
>     not expressible in OWL...
> FWIW, I would like to discuss the general approach before continuing,
> honestly.
> best,
> axel
> 1. http://lists.w3.org/Archives/Public/public-rif-wg/2006Oct/0093
> 2. http://www.w3.org/2005/rules/wg/wiki/CORE?action=recall&rev=14
> 3. http://www.w3.org/2002/09/wbs/38457/RAFQuestionnaire/
> -- 
> Dr. Axel Polleres
> email: axel@polleres.net  url: http://www.polleres.net/

Dr. Axel Polleres
email: axel@polleres.net  url: http://www.polleres.net/
Received on Wednesday, 24 January 2007 10:38:12 UTC

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