(Express v2) Alternative Annex B algorithm

[Ed Barkmeyer]

All,

I have come upon a means of eliminating the "lesser powerset" in Peter's algorithm.
I attach a revision/rewrite of Peter's section 2 and 3 with the revised algorithm.

What this revision does is:

1. Editorial: switch the position of 2.2 and 2.3, so that 2.1 and 2.2 are associated with the schema, but not the instance under
test, while 2.3 and 2.4 are instance specific.

2. Editorial: Revise 2.1 to clarify the subsup graph construction and delete the Powerset stuff (which only applies to section
3).

3. Editorial/Technical: Add the constraints implied by the treatment of ABSTRACT and SUBTYPE in Peter's 2.2 to the section on
formulating constraints (now steps 1 and 2 of 2.2).

4. Technical: replace Peter's algorithm for resolving the multiple-root constraints (old 2.3 step 3, now step 4 of 2.2).

5. Editorial/Technical: Replace old 2.2 with part of what it did (the rest having moved to new 2.2).  This is restated as a
different constraint in new 2.3, and correlates to changes in the evaluated set algorithm in 3.  (This change solves one of the
powerset problems outright -- elimination of combinations of totally unrelated entities.  Peter's algorithm did this
implicitly.)

Note that this does not fix the "greater powerset" problem in the evaluated set generation in section 3, and I do not see how to
avoid that problem.  The powerset seems to be intrinsic to the evaluated set concept.  I can use eliminator rules to prune the
powerset as I build it (as Peter's algorithm specifies), but I cannot find "generator rules" to force the construction of only
valid members.

I believe that the constraint association step (2.2 step 5) can be improved a bit -- not every constraint must be applied to all
the entity types appearing in it -- but I did not do that.

I also believe that the interpretation of SUPERTYPE constraints in 2.4 is not quite correct, or at least needs some
clarification, but that is the subject of another email, when I can produce examples.

-Ed

P.S. I have a marked-up version of Peter's document that shows the actual editorial migration, if anyone cares.  (I originally
thought it would be a fairly compact change, with a few minor other markups, but it didn't turn out that way.)

-- 
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."
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