Declarative programming for the Model part of an application

[pca]

Dear all,

Last week, I raised the question "Could declarative programming be
useful for the Model part of an application ?", and I suggested an
open-source project, Yoopf, to provide such a paradigm in Python.
Stefan told me that the proposal lacked clarity.  I have thus updated
the description, and he now finds it much clearer.  You can find it at
http://www.yoopf.org

So, I would appreciate your feedback again on such a project : can
declarative programming be useful for the Model part of an
application ?  Do you think that Yoopf and its "programming by
formula" paradigm can bring value to python developments ?  How would
it compare to database triggers and stored procedures, for example ?
What could be some typical applications ?

Many thanks in advance !
Pierre C.