How to represent multiple containement relationships between two entities ?

[NicolasAnquetil]

Some entities have multiple containment properties (see also #160):

• TClass is TPackageable and therefore contained in a TPackage + in Java a TPackage is a also a TNamespace, so a class is also contained in this namespace
• same for TMethod contained in a TClass + a TClass is also a TNamespace

We would like

• both relationships stored in the same instance variable (to save memory space)
• both relationships accessible with either accessors (#parentPackage/#parentType and #parentNamespace)

Traits have a #explicitRequirement marker for methods (kind-of 'abstract'), may be TNamespace should declare a #parentNamespace as an explicitRequirement and would force each meta-model to define how to implement it:

• TClass >> parentNamespace --> #parentPackage
• TMethod >> parentNamespace --> #parentType

Ideally there would be a way to declare this in the generator DSL