[wg11] Part 28 Issue : Do we need all this configurability?

[Martin Hardwick]

All

As one of the US organizations that crafted the configuration language
was STEP Tools let me give some background.

We were addressing the first of the three problems identified by Ed

>What we are facing, however, is three problems:
>- The default rendering of an EXPRESS AIM schema into an XML schema will not produce an XML schema intended for use by human engineers who are not STEP experts.  It will not result in increased use of STEP models in ebXML and other business exchanges, because it will be ugly, counterintuitive, and difficult for non-STEP-expert analysts and programmers to work with.  And if it can only be used by STEP experts, why should we not just continue using Part 21 for all STEP exchanges?

By making aggressive use of the configuration language we were able to convert 
several AIM samples into what we thought was reasonable XML. Therefore:

1. We helped add the configuration language to P28.
2. We started a research project to determine how to develop configurations
   for all the STEP AP's.

In our project we quickly determined that the STEP mapping tables seemed to be
the best source of the required information. However, we also found that 
we did not need to generate configuration commands in order to generate the
reasonable XML. Instead we found that we could get better results by using the
mappings to generate an XML ARM interface to encapsulate the XML AIM entities.

There are examples on the STEP Tools home page. Our number #1 project for the
last 6 months has been to automate the production of this XML so that STEP
applications can be programmed at the ARM level and/or the AIM level.

If you want to program something quickly then it is programmed at an ARM level
or at a super-ARM level where even less details of the data model have to be
explicitly programmed.

However, even though we have made much less use of the configuration language
than anticipated the following advantages of the language may still apply:

1. It will let AP developers use different styles of XML for their projects
   if they wish.
2. It will accommodate usage of different styles of XML.

Also if any of the configurations are shown to harm interoperability then they
can be prohibited from STEP usage.

If P28 is going to support both ProSTEP XML and EuroSTEP XML then there is going
to have to be some flexibility in the system. This is not a domain where people
easily surrender their conventions.

I actually think that the P28 project will move forward faster if it worries about
AIM usage only because there are less stakeholders and there is less anticipation
of getting data that is easy to understand and read.

Lastly I am still baffled by why people want to use EXPRESS for ARM models. Surely
it would be more efficient to define the models directly in XML Schema instead of
going through all these convoluted translations.

Martin