[sc34wg3] Topic Maps land and SAM land
Mon, 17 Feb 2003 11:26:33 +0100
Graham Moore wrote:
> However, and I've said this before...
> That the SAM is a refinement of the RM. It is an abstraction that holds true to all the principles of the SAM. But as with all abstractions it has a purpose. That purpose is to expose the core conceptual parts of TopicMaps while hiding some aspects as well.
I don't understand what you mean, can you explain?
> I've also said before and would like some feedback, that we say that
> SAM -> RM -> SAM (is a loss less round trip)
> RM -> SAM -> RM (is a partial loss scenario)
> I think we should embrace this approach and say this is how it works, this is how its designed to work.
Hmm, what you say above implies that you are thinking that a topic map can be
represented solely in terms of the RM...
Let me stress again that the RM is a framework for defining topic map models
(such as the SAM) and that it is not a data model for storing topic maps.
You can (but need not!) base a topic map implementation on the abstract structure
that the RM defines (the topic map graph) but you cannot do this in the absence
of a topic map model.
So, there cannot ever be a transformation like SAM -> RM, it simply makes no sense.
OTH, instances of two different topic map models (e.g. SAM and myOwnHighlySpecializedAM)
can be transformed into each other and if both models have been carefully defined
this transformation can be loss less. (Despite the fact that one model might have
more expressive power than the other)
> There is no 1-1 loss less, two way trip from RM to SAM and back. But this doesnt mean we dont have a two part cohesive standard.
> -----Original Message-----
> From: Sam Hunting [mailto:firstname.lastname@example.org]
> Sent: 14 February 2003 18:16
> To: email@example.com
> Subject: Re: [sc34wg3] Topic Maps land and SAM land
> Thanks. I just wanted something to mull over (besides the original John
> Sowa quotations at:
> http://mars.virtual-earth.de/pipermail/cg/2001q3/003835.html ("I have
> never been happy with the notion of 'data model'...") and at
> http://mars.virtual-earth.de/pipermail/cg/2001q3/003844.html ("there is no
> clear notion of a data model"))
> > > of "metamodel" has gone unanswered as well. Of course, maybe the word is
> > > only there for marketing purposes, so I shouldn't concern myself with it.
> > Try the following from Table 2.1 of the OMG Unified Modelling Language:
> > Metamodel: Defines the language for specifying a model
> > or the definition given in the OMG Modeling Glossary in Annex B of the
> > specification:
> > "A model that defines the language for expressing a model."
> > (I prefer the first as the second is circular.)
> > In fact UML also defines metamodel as "An instance of a meta-metamodel"
> > where a meta-metamodel is defined as "The infrastructure for a metamodelling
> > domain" and defines a model as "Describes a language to define an
> > information domain".
> > Whether or not you consider the use of the term metamodel within UML (which
> > is littered with the term) as an "agreed-upon definition" is up to you.
> Well, it seems there are three (one of which is circular) so there are two
> available to us. Which one do we use? Unless, of course, we have a fourth
> definition. Or indeed if the term is just in the text for marketing
> purposes and I don't have to obsess about it. In the former case, I guess
> it's not an issue, since it would be subsumed under the larger task of
> writing the glossary for the SAM. In the latter case, it isn't an issue
> because "data model" just becomes a phrase that achieves a certain comfort
> level for an audience (as Sowa puts it), rather than a term -- not that
> there's anything wrong with that.
> Martin -- "Be open to the possibility that being is!"
> > Martin Bryan
> > IS-Thought: Thinkers for the Information Society
> > 29 Oldbury Orchard, Churchdown, Glos. GL3 2PU, UK
> > Phone/Fax: 01452 714029 E-mail: firstname.lastname@example.org
> > Thought of the week:
> > Is "being" necessary? Won't "known as" suffice?
> > _______________________________________________
> > sc34wg3 mailing list
> > email@example.com
> > http://www.isotopicmaps.org/mailman/listinfo/sc34wg3
> Sam Hunting
> eTopicality, Inc.
> Co-Editor, ISO Reference Model for Topic Maps
> Topic map consulting and training: www.etopicality.com
> Free open source topic map tools: www.gooseworks.org
> XML Topic Maps: Creating and Using Topic Maps for the Web.
> Addison-Wesley, ISBN 0-201-74960-2.
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