Part28: schema population text from Part 21 Annex F

[Ed Barkmeyer]

Martin,

Thanks. This is the information I needed.

Martin Hardwick wrote:

> Part 21 ed2 Annex F is not in error.
> 
> The checking algorithm operates in two phases:
> 
> 1. Define the population be picking the sections containing
>    the instances to be checked.
> 2. Evaluate the EXPRESS constraints against the defined
>    population.
> 
> Transitive references are not allowed to make sure that the
> population to be tested in precisely defined. If you start
> hunting for transitive references then the population will
> become unlimited (what about USEDIN etc).

Yes. This was the other possible interpretation of the intent of Annex F.  If this is what was intended, then the text I
produced 10 days ago provides the analogous text for Part 28, and I don't need to change it.

Anent Part 21 Ed.2, however, this simply results in a different SEDS.  The current text of F.2.3 makes no mention of the
handling of references made from the entity instances that are themselves included by reference.  It should say that where such
references refer to instances outside of the population, their values will be treated as unset.  (This is the analog to the
wording of F.2.2 and to the proposed wording for Part 28.)  And the text should contain a Note that explicitly says what Martin
writes above, and preferably an Example that contains an "unset" attribute value or UsedIn result.

So, from Martin's contribution, I understand that 
- I am to make no change to the proposed text of the "valid populations" Annex for Part 28; and
- I am to write up a different SEDS for Part 21.

Does the committee agree? 
Are there any other errors or bad examples in the proposed text?

Thanks,
-Ed

-- 
Edward J. Barkmeyer                       Email: edbark at nist.gov
National Institute of Standards & Technology
Manufacturing Systems Integration Division
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