- From: Phil Tetlow <philip.tetlow@uk.ibm.com>
- Date: Wed, 26 Jan 2005 11:30:25 -0500
- To: Jeremy Carroll <jjc@hplb.hpl.hp.com>
- Cc: public-swbp-wg@w3.org, ewallace@cme.nist.gov, Grady Booch <gbooch@us.ibm.com>
Jeremy,
Ok, so I hope that a light hearted reply is in order?
Interesting that you prefer to concentrate on the conclusions. I
personally felt that additional text was needed to recognised the excellent
work that both the ODM and UML teams have undertaken to get us to where we
are today. I further consider that the material in sections 7 & 8 of this
document is indeed important. It provides an extremely valuable context for
those who do not have the advantage of being as familiar with this area as
recognised experts such as yourself - This type of material is
unfortunately lacking within our community. Nevertheless, point taken - I
am a consultant by trade, so 'fluff' is my native dialect, only we have a
technical term for it....For me it is harder to be concise. I must
apologise.
I think its really important to get across is the obvious overall value of
this document, as well as the individual recommendations it makes - right
or wrong. It is surely superb that such a comprehensive piece of work has
been undertaken at this opportune time and I'm enthused that it will help
to 'align' current thinking across a number of desperate camps.
I look forward to your considered opinion in due course and again apologise
for the length of this mail. I didn't have time to write a shorter one!
Kind Regards
Phil Tetlow
Senior Consultant
IBM Business Consulting Services
Mobile. (+44) 7740 923328
Jeremy Carroll
<jjc@hplb.hpl.hp.
com> To
Phil Tetlow/UK/IBM@IBMGB
26/01/2005 09:56 cc
public-swbp-wg@w3.org,
ewallace@cme.nist.gov, Grady Booch
<gbooch@us.ibm.com>,
Cliff.jones@newcastle.ac.uk
Subject
Re: OMG Ontology Metamodel
Definition Review
Hi Phil
I think this review could benefoit from being halved in length.
The main thing you say is:
> So my preference would not be to construct the ODM as ‘an aggregate of
> equal and independent metamodels’ (as described and illustrated in
8.4 and
> 9.0). Instead I think that a ‘hub and spoke’ based model would be more
> valuable, with the UML acting as the hub. Where features of the five
> remaining metamodels cannot be represented directly, then emphasis
should
> be placed on either constructing new UML mechanisms for direct
> representation or establishing suitable compromises and translations for
> the purpose of unification. The reasoning behind this approach comes
purely
> form the huge gains that unification brings and not out of any
preference
> for the UML as a descriptive medium. ‘Pick your poison then drink’
should
> be the message, so long as everyone drinks the same poison. Then at
least
> we can all meet in hell afterwards and compare notes, right?!
the rest seems to be fluff.
FWIW, I think I disagree with the above para - I'm behind with my own
review, I will get it out tomorrow.
Jeremy
Phil Tetlow wrote:
>
>
>
> I have now provisionally reviewed most of the OMG’s Ontology Definition
> Metamodel (ODM) document and on first reading consider section 14 (ER
> Metamodel) to be a recognised subset of the UML which, as such, does not
> warrant significant comment. Bob Lojek (IBM) has also kindly reviewed
> section 10 (UML2 Metamodel) and his findings are appended at the end of
> this mail.
>
> Firstly I must state that I consider the ODM paper to be a broad and
> significant embodiment of current thinking on the representation of
> ontologies. It extensively collates and articulates a number of
> perspectives that are of great value and I especially like the material
> presented in section 7 (Usage Scenarios and Goals). I find, however, the
> material presented in section 8 (Design Rationale) and 9 (ODM Overview)
to
> be somewhat misdirected.
>
> Section 8.2 presents reasoning as to why the ODM cannot be fully
> represented in the UML, specifically stating a number of acknowledged
> weaknesses within the language. Nevertheless I think that this is being
> somewhat unfair and one must remember two important points about the UML
as
> a descriptive tool:
>
> o Firstly a primary purpose of the UML is ‘U’nification. This, by
> definition means that it has to cover a lot of ground, hence loosing out
on
> specialisation in some cases in favour of a deliberately generalised
> approach. The paper acknowledges this fact but does not appear to convey
> the true values behind a unified approach to modelling.
> o Secondly the UML is a living ‘L’anguage and as such it should be
> viewed as an evolving entity in its own right, capable of change to meet
> the requirements of most of the new, valid contexts in which it might be
> used. Just because the UML 2 does not natively support specific concepts
> required for the accurate representation of certain types of ontology
does
> not mean that it should or will not in the future. Perhaps, therefore, it
> should be job of this Working Group to recommend amendments for inclusion
> in later versions of the UML. If this means wholesale architectural
changes
> or the introduction of completely new schematic representations then so
be
> it. Most agree that graphical ontology conceptualisation needs to be
based
> closely around a Direct Graph theme and even if either Profiling or
> Stereotyping cannot accomplish this directly in the UML 2 for more
> specialised ontologies, the mapping of predicate associations is central
to
> its ethos and culture of those who use it professionally for whatever
> purpose as part of their daily practices. Adding more types of graphing
> schemes to cope for formal and specialised ontology representation is
> hardly going to be rejected out of hand.
>
> Nevertheless, I agree in particular that there are problems with cross
> meta-level representation in the UML as it currently stands and that
these
> indeed may well cause barriers to successful ontology modelling.
> Nevertheless such problems have been encountered a number of times
already
> in the modelling community and the use of proper and structured object
> referencing mechanisms has traditionally surmounted such problems.
> Admittedly this adds a layer of complexity on top of any raw ontology
> itself, but that is the nature of the beast – formal representation often
> needs additional ‘straight jackets’ to accommodate more specialised ways
of
> thinking.
>
> So my preference would not be to construct the ODM as ‘an aggregate of
> equal and independent metamodels’ (as described and illustrated in 8.4
and
> 9.0). Instead I think that a ‘hub and spoke’ based model would be more
> valuable, with the UML acting as the hub. Where features of the five
> remaining metamodels cannot be represented directly, then emphasis should
> be placed on either constructing new UML mechanisms for direct
> representation or establishing suitable compromises and translations for
> the purpose of unification. The reasoning behind this approach comes
purely
> form the huge gains that unification brings and not out of any preference
> for the UML as a descriptive medium. ‘Pick your poison then drink’ should
> be the message, so long as everyone drinks the same poison. Then at least
> we can all meet in hell afterwards and compare notes, right?!
>
> From my point of view the UML, for all its faults, has proved its worth
> many times over in the hard faced commercial reality that is significant
> systems’ development. The same is not yet true of ontology representation
> and embodiment, yet its potential is plainly apparent to all who take the
> time to investigate properly. If, as I suspect we all agree, we want to
> make the power of knowledge representation, through graphical ontology
> modelling, available to a much wider audience, then perhaps now is the
time
> to be pragmatic, rather than academic, and allow the UML to maintain the
> upper hand? Surely only the most adventurous gamblers amongst us would
not
> admit that, for now, the UML is safest ‘bet in town’.
>
>
-----------------------------------------------------------------------------------------------------------
> -
>
> Bob Lojek wrote:
>
> Phil,
>
> Here are my comments:
>
> Talk to you tomorrow
>
> Cheers, Bob
>
>
> The approach has 4 levels of abstraction called metalevels,
>
> M0, M1, M2 and M3; each is increasingly abstract as Mn increases and
> decomposable in the opposite direction.
>
>
> 10.2.1 UML Kernel
> ---------------------------
>
> Page 64: "There is no direct linkage between Association and Class. The
> linkage is mediated by Property."
>
> In the M1 model, why are association stereotypes not used, although table
> 11 and 12 indicate they are?
>
>
> 10.2.2 Class and Property - Basics
> --------------------------------------------------
>
> Page 67: "That is there are cases in which a relational database
> implementation would use a
> compound key to identify an instance of a class."
>
> This is a conditional association, for example a foreign key that points
to
> several primary keys depending on runtime values. Shouldn't this be
> described a the M0 level?
>
>
> In the example
>
> (Embedded image moved to file: pic04092.jpg)
>
> I would stereotype the association as <<enrolled>> and perpaps the
> property as well. This will make it easier to process to downstream
> systems.
>
> Also the relationship of grade to enrolled is unclear to me, looking at
the
> diagram and this table.
>
>
> (Embedded image moved to file: pic16522.jpg)
>
>
>
> 10.2.3 More Advanced Concepts
>
> How will namespaces be addressed in the UML model? We are, for example,
> using packages.
>
>
> This is basically a comparison between OWL and UML 2, why not go back to
> the language definition of OWL and map the coressponding UML equivilants
to
> it. This was done in "Table 18 Common Features of UML and OWL" but in the
> opposite direction.
>
> Regards
>
> Phil Tetlow
> Senior Consultant
> IBM Business Consulting Services
> Mobile. (+44) 7740 923328
>
>
> ------------------------------------------------------------------------
>
>
> ------------------------------------------------------------------------
>
Received on Wednesday, 26 January 2005 16:26:52 UTC