Part28: schema population text from Part 21 Annex F

[Martin Hardwick]

Ed,

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).

The defined algorithm gives the user control over how much
gets pulled into the reference checking.

I strongly suggest you use the Part 21 ed 2 algorithm in 
Part 28. For XML the meanining of transitive reference could
get completely out of control because of the power of XML
referencing.

Martin Hardwick

Martin Hardwick



>
>> Good issue against Part21 edition 2. I do think we need to consider also
>> "the things the referenced instances themselves reference". 
>> For example, if we reference
>> an instance of circle, it would mean nothing to check the validity of the
>> circle without checking the validity of the cartesian_point that defines its
>> center.
>> My recommendation is therefore that you update Part28, considering
>> "references transitivity".
>
>I agree, and I will do that for Part 28, as long as the acting project 
>leader also agrees.  (I was directed by the committee to
>prepare wording to match Annex F of Part 21; we are now proposing wording 
>that does *not* match, although we believe we are
>correcting an error in Part 21.)
>
>Who will submit the SEDS against Part 21?
>
>Thanks,
>-Ed
>
>-- 
>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."