Currently FM3 does not allow other default, question is if we really need that, as we have no usecase yet. @Lukas, how is it in Magritte?
In Magritte default values are nil by default, also for numbers and booleans. Attributes can have a different default value. As Toon explained I have examples where the default value for a boolean is true or the one for a number is 17 ;-)
Do you have non-primitive or non-constant, ie derived, default values?
In general, default values do not fit well into a meta-layer architecture, as a value of the model level is to be specified at the meta-level. A default value can be constant or derived and primitive or non-primitive, of these cases only constant primitive default values fit well with a meta-layer architecture.
All other cases require an expression written in a query language. Which is maybe better to be post-poned for a later release of FM3, we should first get the simple stuff right.
AA