So you say you want a revolution

[Martin Hardwick]

Dream on people. The "Lords" of EXPRESS may state that
you can only use GENERIC with ABSTRACT entities but it
will be a two pico-second interval before a user group
insists that they want to read and write data defined 
by these entities so that they can "early test" their 
code.

Martin


At 02:46 PM 10/26/2001 +0200, Bernd G. Wenzel wrote:
>Dave,
>
>what you're suggesting would work, but I wouldn't like to do it
>this way. Your wording at least suggests, that it is not your
>favourite solution either.
>
>If I understand Alan correctly, he's complaining about the
>representation of a partial entity instance in an exchange file,
>if external mapping is used.
>
>Under all circumstances EXPRESS-2 makes sure, that we know for
>every legal entity instance the type for each and every attribute
>(although it may be a SELECT type). It is IMHO not the job of P21
>to specify, what should be done with instances, which are
>incorrect according to P11. So we are safe.
>
>When we now come to the external mapping, I know, that some, but
>not all, implementors do not like it, because they have to parse
>the whole instance, before they know what the damned thing is
>(validation) or maps to (processing). This is the situation with
>EXPRESS-1 already. So it is not impacted by the capabilities of
>EXPRESS-2.
>
>If my understanding of Alan's argument is correct, the complexity
>was introduced when we allowed attribute redeclaration. We have
>not added an additional quality here.
>
>:-) Bernd
>
>----- Original Message -----
>From: <david-price at btclick.com>
>To: <wg11 at steptools.com>
>Sent: Friday, October 26, 2001 1:32 PM
>Subject: RE: Re: So you say you want a revolution
>
>
>>
>> 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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