[Modeling-users] Pythonic, and non-XML, Model description

[Mario R. <ma...@ru...>]

Hello,

following comments about the XML model (on and off the list) and
how it can be improved or redone altogether, i started thinking about 
it...
And (to be able to get it out of my mind and get to some other work ;-)
here is a proposal for a pure python description of the model. It 
follows
the XML closely, and in fact may always retain compatibility (at least
generation of XML from the python model, which will be trivial).

The behaviour in gnereal would stay the same as the XML way of
doing things, namely form this model you would generate the classes
and the db schemas.

Some differences are choice of default values, and that key and locking
attributes are defined on attributes and relations rather than entities 
;)

As an exercise, I have taken the sample model in the distribution:
testPackages/StoreEmployees/model_StoreEmployees.xml
and re-expressed it in this pythonic way. Apart from readability and
losing of some verbosity, other gains are "executability" and
dynamicity -- it could be very easy to modify a model at runtime, if
you would ever want to do that. Also, given that a model now becomes
a module in and of itself, it gains from what modules have to offer,
such as self-tests. And, speed of course, as i see no reason why
this model object would also not serve as the model object in memory
at runtime (but that's for Sebastien to confirm) -- thus loading the
model is equivalent to "from MyModel import model".

Can you please take a look at the attached 2 files;
PyModel.py -- defines the classes (signatures for) for, and documents
the rules for, a PyModel instance
sample_PyModel.py -- re-expresses the StoreEmployees model

What does everyone think?

mario