So you say you want a revolution

[david-price at btclick.com]

Alan,
Your reply presupposes how P21 with E2 would work. One could also think of any attribute that was not instantiable as simply a pattern/template/constraint for modelers that does not affect data. So, P21 could say to ignore any attribute that does not have a type that is instantiable. Then these attributes, all with the same name, would simply appear in the subtypes, not in the ABSTRACT ENTITY. I'm not necessarily suggesting that I think this is the best approach. I'm just suggesting that there is more than one way to address this issue.

Cheers,
David


Original Message:
-----------------
From: Alan R Williams alanrw at cs.man.ac.uk
Date: Fri, 26 Oct 2001 11:44:13 +0100 (BST)
To: wg11 at steptools.com
Subject: Re: So you say you want a revolution



> Date: Thu, 25 Oct 2001 17:05:09 -0400
> From: Ed Barkmeyer <edbark at cme.nist.gov>
> X-Sender: "Ed Barkmeyer" <edbark at mailhost.cme.nist.gov>
> X-Accept-Language: en,pdf
> To: Martin Hardwick <hardwick at steptools.com>
> CC: edbark at nist.gov, wg11 at steptools.com
> Subject: Re: So you say you want a revolution
> 
[mega snip]
> None of this is true.  The only entity types that can actually appear directly 
in an exchange are the leaf types of the
> inheritance tree, and in those types, every inherited generic attribute must 
be re-declared to a specific Express:1994 data
> type.

Isn't that only sort-of true?  In a Part 21 file, you could use the
external form for complex entity instances.  In the partial for the
abstract entity declaration, the attribute value needed would be generic,
wouldn't it?

> So when you look at an instantiable exchange schema, all of those generic 
attributes disappear!

[mega snip]
> -Ed
> 
> P.S. I want a revolution, but I would start by defining a meta-model that does 
not have a one-to-one map into either Express or
> UML.  I'm not likely to find many pragmatists flocking to my red banner. So 
since we have a working kludge, let's just keep
> kludging it, until the real revolution buries us. ;-)
> 
> -- 
> Edward J. Barkmeyer                       Email: edbark at nist.gov
> National Institute of Standards & Technology
> Manufacturing Systems Integration Division
> 100 Bureau Drive, Mail Stop 8260          Tel: +1 301-975-3528
> Gaithersburg, MD 20899-8260               FAX: +1 301-975-4482
> 
> "The opinions expressed above do not reflect consensus of NIST,
> and have not been reviewed by any Government authority."

Alan

Alan Williams, Room IT301, Department of Computer Science,
University of Manchester, Oxford Road, Manchester, M13 9PL, U.K.
Tel: +44 161 275 6270      Fax: +44 161 275 6280

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