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Subject: PMTM4 templates vs. TMCL (was: Re: [topicmaps-comment] RE: OASIS vsW3C)
Let me take this opportunity to explain the relationship between association templates in PMTM4 and TMCL. In my view, far from being mutually adverse in any way, PMTM4 and TMCL need each other. PMTM4 merely explains how sets of constraints -- constraints that might be expressed in TMCL -- actually participate in the Topic Map as topics. The constraints that will be established by TMCL expressions will also be reifiable as topics. One of the purposes of PMTM4 is to show how those topics are always findable in the topic map from the perspective of the assertions that are constrained by them. Surely this is a good and necessary thing (see final paragraph below). Neither the Topic Maps paradigm nor PMTM4 constrain how the subjects of topics can be expressed ("indicated"). TMCL is going to be a perfectly good way of expressing such subjects, and, I hope, better than most. I would be deeply disappointed in the outcome of the TM standardization process if we abandoned one of the cardinal requirements that has always driven the design of TMs. That requirement is that any subject that affects the meaning of a topic map must be reified as a topic in that same topic map. This is the reason why * association templates (association classes) are topics, * associations are topics (i.e., they are topics in that they can be role players and scope components), * association roles (role classes) are topics, * scope components are topics, and * recognized player of role classes are topics <<-- this is the one we're talking about. Subjects that participate in some topic map in any special way must always be reified as topics, just like any subject. The "specialness" of the participation of such topics must be rigorously accounted for in the model of what topic maps mean. We must resist the temptation to privilege any subjects in such a way that they somehow participate in a topic map, but, at the same time, they're not *in* the topic map. * Knowledge is knowledge. Either it's there, or it isn't. * Either topic maps are self-describing, or they aren't. * Either all subjects are reified as topics, or they aren't. We can't afford to create a situation in which the constraints that govern some class of association aren't required to be reified as topics, or in which such topics aren't findable in some rigorous, predictable way. PMTM4 proposes such a rigorous, predictable way. In any case, even leaving PMTM4 aside for the moment, the specification of how the role-player constraint topics are connected to the associations that they constrain is quite orthogonal to the issue of how those constraints are expressed (e.g., in TMCL). -Steve -- Steven R. Newcomb, Consultant srn@coolheads.com voice: +1 972 359 8160 fax: +1 972 359 0270 1527 Northaven Drive Allen, Texas 75002-1648 USA
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