Wow, I finally went through the complete Core::Abstractions chapter and covered all the concepts. Time to sit back and look at the complete diagram.
Very central concepts are those introduced in the ownerships and namespaces packages. A lot of associations in other packages subsets the Elementwner (respective Namespace:namespace), ElementwnedElement (respective NamespacewnedMember) and Namespace:member properties. These seem to be the 'wires' that connect the classes and create a structure together with the inheritance tree. Propably I should write a list of all the owner and member relations between the classes.
The next chapter Core::Basic will define a minimal modeling language which is reused for EMOF (essential meta object facility). I will skip this in favor of the Core::Constructs which focuses on concrete classes based on Abstractions. Whenever necessary, I'll include any specialities of Basic in my posts about Constructs.