Re: OMG Ontology Metamodel Definition Review





Many thanks for your detailed comments.

Returning to the 'hub and spoke' debate (hopefully for the last time).
Providing the reasoning behind the eventual architecture, as you have done
here, has provided exactly the type of information I would have liked to
have seen in section 9. A more centralised approach to the use of a
language like the UML, as you first tried, of course has obvious appeal,
but logical architecture design is almost always obstructed by
practicality, as we have stated - thank you. I fully appreciate that
incompatibility between representations may well have proved insurmountable
on this occasion and hence consider the architectural approach presented to
be absolutely fine and I further must congratulate you on the excellent
work that you have all done. I further look forward to seeing the good work
coming out of QVT. I also absolutely accept that, even if the UML (1 or 2)
could have been adopted in a central role there would have been a problem
with implicit and overly complex semantics, and these are issues that
really have concerned me for some time now, but I don’t think that they are
common to just these circumstances.

Unification is hard (clearly), generally takes a very long time and is
almost impossible in some cases - just like peace - but the architectural
intent behind such an aim is worth the effort. If unification is to be
achieved then it will have to involve a concerted change effort across a
number of disparate schools of thought to increase commonality. The second
point in my original email was that the UML should be as much a part of
this change process as any other participating metamodel. Given that the
ODM is the first significant piece of work in this area I wondered if it
might have been relevant to raise the possibility of appropriate change(s)
for inclusion in the next UML standard.

Kind regards

Phil Tetlow
Senior Consultant
IBM Business Consulting Services
Mobile. (+44) 7740 923328


                                                                           
             "Elisa F.                                                     
             Kendall"                                                      
             <ekendall@sandsof                                          To 
             t.com>                    Jeremy Carroll                      
             Sent by:                  <jjc@hplb.hpl.hp.com>               
             public-swbp-wg-re                                          cc 
             quest@w3.org              Phil Tetlow/UK/IBM@IBMGB,           
                                       public-swbp-wg@w3.org,              
                                       ewallace@cme.nist.gov, Grady Booch  
             27/01/2005 14:18          <gbooch@us.ibm.com>,                
                                       Cliff.jones@newcastle.ac.uk         
                                                                   Subject 
                                       Re: OMG Ontology Metamodel          
                                       Definition Review                   
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           





Hi All,

First, thank you for taking the time to read through our submission, and
thanks in particular to Jeremy for
the detailed comments.  I will take them back to the team personally and
ensure that we address them all
appropriately.  This kind of feedback is incredibly valuable to us, as
we truly want the specification to be
useful and widely adopted.

A few thoughts on the hub and spoke conversation -- we initially sought
to do exactly that, at first using
the core UML constructs as a basis for that work.  We failed miserably
for a number of reasons, in part
because of using UML 1 tools rather than UML 2, but also because there
were serious impedance
mismatches between the implicit semantics of some UML constructs and our
understanding of the
related OWL constructs (e.g., associations/association classes vs. OWL
properties, individuals in OWL
and UML instances, etc.).  We were also concerned about unintended
semantics, or overly complex
semantics, creeping into the picture, making it difficult for downstream
reasoners to leverage the
results.  We then looked at creating a core ODM metamodel that could be
used as the hub for the set
of metamodels developed, but did not find enough commonality (although
there is significant overlap
in some cases).  Lewis Hart and Patrick Emery spent a great deal of time
developing the DL metamodel
which is now informative, in fact, to be used for that purpose, but we
abandoned it for a number of
reasons, including lack of any clear "standard" DL aside from OWL.
Arguably, there are a number of
core DL constructs that are represented in the DL metamodel, but it was
not our intent to develop a
new knowledge representation language, simply to model those that were
already in use.  Thus, we
elected to use the OWL Full metamodel as a vehicle for mappings in and
out of the ODM.  All of the
mappings will be more fully specified (hopefully using a specification
that is called MOF Query/View/
Transformation, or QVT) during the finalization phase of the
specification -- which I think may address
Jeremy's concern about whether or not the mapping is sufficient for
implementers to use.

More recently, we've been asked to provide forward and reverse mappings
from SCL to UML/MOF
as well as to OWL, and mappings from the ER and Topic Maps metamodels to
SCL.  Pat Hayes, who
was a great help to us in developing the SCL metamodel and mappings, has
offered to help us with
some of this work, so our intent is to do as much as we can given the
resources and time, without
risking delay in adoption of the work we've already done.  Likely much
of this will happen during the
finalization phase of the specification's cycle through the OMG, again
using the MOF QVT to document
the mappings once that specification stabilizes.  Some would argue,
then, that it makes more sense
for the SCL metamodel to be the hub, given that it is more expressive
... but we wanted to ensure
that developers who did not need that level of expressivity could
effectively use the ODM as a
basis for model interoperability.  So -- we have (or will have)
essentially two "primary" metamodels
(three including the combined RDF/RDFS metamodel) that we leverage for
forward and reverse
engineering, and others that can be used to leverage existing resources
as a basis for ontology
development in UML.

I hope this helps clarify the intent.  Please feel free to point out
anything that might preclude us
from achieving this, or any thoughts that would improve the
specification in general.  We really
are delighted to see that it is getting serious attention, and welcome
as much feedback as people
have time to provide.  Since my focus has been on the SCL material in
particular, I would
also appreciate any feedback on that work for those of you who have time
and inclination.

Best regards,

Elisa


Jeremy Carroll wrote:

>
>
> My own nervousness was less well-informed.
> I believe this document is an important one, and that we should be
> encouraging it to completion as quickly as possible.
> Hence comments should, in my view:
> - help correct the document
> - point out important weaknesses
> - or be supportive
>
> As far as I could tell, and I am glad that someone better informed
> about UML than me tended to agree, the hub-and-spoke comment did not
> point out an important weakness, but articulated an alternative
> design. To fully address this comment I think would take quite some
> time, since it's a few steps backwards before going forwards, and I
> don't see (any/enough) benefit for this cost. (All process - no
> content :( )
>
>
> Jeremy
>
>
>

Received on Friday, 28 January 2005 09:22:13 UTC