Dear Rich, (01)
> Thanks Matthew,
>
> You've written a large number of papers on modeling - my
> congratulations for
> being so prolific. Your papers seem to begin with the concept of data
> modeling and then go into the proper principles for modeling.
>
> But I'm looking for ways to use existing database tables and to
> discover the
> classes and relationships that, by chance, went into the original table
> design. (02)
[MW] If you follow the steps in the "traps" sections of "Developing High
Quality Data Models" you will find yourself doing just that. (03)
In my experience, commercial databases are developed in a
> haphazard
> way for nearly all commercial applications without the luxury of
> careful
> modeling. That's especially true of the applications developed as
> requirements are being discovered and changes are requested by users
> that
> may not meet the best practices of modelers. Database designers are
> usually
> upset to see the way the databases turn out when created in this de
> facto
> way instead of in a well designed, carefully orchestrated way. (04)
[MW] Just so.
>
> So if you must begin with an existing database's table designs, how can
> a
> reasonable class model be developed for that legacy database? Are
> there
> automatic methods for generating the As-Is class models? (05)
[MW] The only other thing that I am aware of is the Boro method, mentioned
here recently, which starts from the data (and you really need to look at
how people have used a database to be confident of what it is all about). (06)
>
> Suggestions, URLs, replies appreciated.
>
> Thanks,
> -Rich
>
>
>
> Sincerely,
> Rich Cooper
> EnglishLogicKernel.com
> Rich AT EnglishLogicKernel DOT com
>
>
>
> -----Original Message-----
> From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx
> [mailto:ontolog-forum-bounces@xxxxxxxxxxxxxxxx] On Behalf Of Matthew
> West
> Sent: Saturday, January 31, 2009 1:34 AM
> To: edbark@xxxxxxxx; '[ontolog-forum] '
> Subject: Re: [ontolog-forum] Is there something I missed?
>
> Dear Rich
>
> >
> > > I have always considered the definition of an RDB-class
> > correspondence to be
> > > partially in the mind of the modeler, not in the RDB structure
> > itself. I
> > > know of no formal definition of what a RDB-class consists of, which
> > would
> > > provide a rigorous foundation for translating RDBs to classes with
> > one
> > > exception; there is at least one class per table. Modelers may
> often
> > add
> > > definitions of subclasses within a table, but that's usually some
> > form of
> > > correspondence between groups of columns from a table that fit
> within
> > the
> > > human "chunk" size of 7+/-2 concepts. So it seems every bit as
> > subjective
> > > as any other method of constructing classes from data. Data mining
> > (and
> > > text mining) consists of discovering those subclasses, along with
> > classes
> > > that relate one table to other(s).
> >
> > I would not dispute any of this.
> >
> > > Do you have reference(s) (URLs especially) to other documented
> points
> > of
> > > view which might more rigorously define how the RDB translates into
> > classes?
>
> [MW] I did some work that effectively does this about 15 years ago,
> which is
> captured in a document called "Developing high Quality Data Models".
> Part of
> it is about finding the hidden classes, and part of it is about not
> hiding
> them in the first place. You can find it here:
> http://www.matthew-west.org.uk/Publications.html
>
> or just type "High Quality Data Models" into Google.
>
> Regards
>
> Matthew West
> Information Junction
> Tel: +44 560 302 3685
> Mobile: +44 750 3385279
> matthew.west@xxxxxxxxxxxxxxxxxxxxxxxxx
> http://www.matthew-west.org.uk/
>
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>
>
>
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