Comments on Impact of STEP Modularization

[Pascal Huau]

Dear Greg and Dave,


You wrote in a previous mail:
> >2) Clause 2 - 6th paragraph - Disagree on statement that AP made up of
AMs
> >do not need a long form.  Several reasons: a) If an AP does not have a
long
> >form, then a user who attempts to implement the AP will not know what the
> >EXPRESS constructs are for the AP.  b) An AM may be published with
several
> >corrections, the AP needs to know version of the EXPRESS is valid for the
> >standard. c) The Extensible Selects need to be completed by the AP.  d)
The
> >proliferation of AMs would result in several new/modified Extensible
> Selects
> >- how does the AP reconcile the different Extensible Selects.
>
> Agree that the long form question remains an open issue to be worked.
> Disagree on completion of EXPRESS selects in AP, there really isn't an
> AP schema. See next issue.
>

I am rather surprised by the fact that the question of finding or not an AIM
schema in a AP using modules is still to be discussed.
Are you really saying that you are promoting the design of application
modules without knowing or having decided how the APs that will use them,
should be built?

>From a more technical point of view, I would say that as long as we do not
have a unique, standard, implementable and implemented algorithm enabling to
merge AMs in a common
Express schema, the presence of an AIM schema in an AP using modules should
be mandatory.
A good indicator of the difficulty to switch from several Express schemas to
a big one can be obtained from the experience with translations
 from short to long form schemas: most of time, the generation was partly
automated but also completed by
hand (because of the difficulty to remove unwanted subtypes, to adapt select
types, ...).
In addition, if there is an AIM schema, you have one reference. Whereas with
several schemas, some of them with one or more TCs, it would be much less
obvious  to be sure that two implementors have really worked on the same
basis.
Then, the industrial companies that implement STEP APs presently are, most
of times, using toolkits that can only process only one Express schema,
associated in many PDM cases, with one ExpressX schema.
Therefore, requiring an AIM schema, at least for first APs using modules,
seems to me much safer and easier for implementors.


Regards,
Pascal Huau
Association GOSET
107,111 avenue Clemenceau
92000 Nanterre
France