- From: Phil Tetlow <philip.tetlow@uk.ibm.com>
- Date: Fri, 28 Jan 2005 04:25:48 -0500
- To: "Elisa F. Kendall" <ekendall@sandsoft.com>
- Cc: Jeremy Carroll <jjc@hplb.hpl.hp.com>, public-swbp-wg@w3.org, ewallace@cme.nist.gov, Grady Booch <gbooch@us.ibm.com>, Cliff.jones@newcastle.ac.uk
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