Calling the textgen procedure for super concept

I'm afraid there is no way to invoke TextGen for the super concept. But if you have no text gen declared for the concept, the inherited one is used.

Instead you can extract text-generation code into an operation an reuse it in append clauses. Create a LanguageTextGenDeclaration root and declare an operation.

I've called the toString() method in the TextGen procedure. Other code I've implemented within the Behavior Aspect.

I've found, that TextGen declared for concept interface is not inherited. For abstract concept it works, but not for interface. Generation results into "<!TextGen not found for <concrete concept>!>"

Concept interface is very similar to java interface, except it can provide the default implementation of behavior methods and constraints. It cannot provide TextGen though.

It is not intuitive. So does TextGen aspect is absolutely useless for concept interfaces? If so, may be it should be forbidden?

Yep. MPS-14245