Having participated in projects where the model went right down to an implementation level, whether that's for communication or direct code generation, I find it pretty unworkable at any non-trivial scale. Try getting version control set up for a large, very detailed model for instance where many people have to be involved, we used to partition our heavily to try to deal with that, but it was always far slower and more cumbersome for detail work than the code was. Better to just represent the high-level architecture, principles and idioms in the model (and it doesn't even need to be in a modelling tool for that, in fact something more free-form like a wiki was often more powerful) and let the implementors instantiate / specialise the patterns appropriately. Another reason a wiki was better than a formal model was that these implementors could feed back any specialisations or issues for peer review far more easily.
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