Ed2 short to Ed1 long conversion (plus language version ids)

[Wilson, Peter R]

    Are we having fun yet?

    Just to check that I have understood Ed correctly, my precis of his
comments (Sent May 15, 2002 7:30AM) is:

o An Ed2 short to Ed1 long conversion process must first generate an Ed2
long and then convert the Ed2 long to Ed1.

o An Ed2 schema can only interface to Ed2 schemas (if an interfaced schema
is actually Ed1 it is treated as Ed2).

o An Ed2 schema to Ed1 schema conversion algorithm must say that interfaced
EXTENSIBLE types are replaced with corresponding TYPE declarations. 

o An Ed1 long form in a module is useless (PW: But what if all the schemas
that the long is based on are native Ed1?).
PW: But an Ed2 long form can be used by an AP.


    We now have 3 possibilites for an EXPRESS schema:
1) (native Ed1) It was written as an Ed1 schema;
2) (native Ed2) It was written as an Ed2 schema (but it might only use Ed1
constructs)
3) (mapped Ed1) It was originally written as an Ed2 schema but has been
converted/mapped to an Ed1 schema.

    Also, there is no guarantee that there will be any more information
about a schema than uncommented EXPRESS code.

    For SC4 purposes it seems essential to me that these three different
kinds are distinguishable (as part of the EXPRESS language) as there are
limitations on how they may be used together.

    Also, remember that SC4 is not the only group that uses EXPRESS, and
Shtolo is internal to SC4 because the author of Part 21 refused to
contemplate multiple schema data.

    Do not discard the Edition 2 language version identifier, add an
identifier for mapped Ed1, and put the appropriate identifier (none for
native Ed1) with each schema.

Peter W.    

Dr Peter R. Wilson
Boeing Commercial Airplanes
PO Box 3707, MS 6H-AF, Seattle, WA 98124-2207
(Package Delivery: MS 6H-AF, 1601 E. Valley Frontage Road, Renton, WA 98055)
Tel: (425) 237-3506, Fax: (425) 237-3428
Email: peter.r.wilson at boeing.com
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