my small sample-application has a simple tree-like structure where i want to build a behaviour very similar to the "."-Operator in Base-Language (f.e. class.method or class.field). I searched within the code for base-language to find the place where these restrictions to the possible (sub)elements occurr (monkey see, monkey do ;-)) . Not very successful. Can you give me hint, where to look for the implementation of such a sample?