To make the analysis and design process more effective, a more specific framework, than generic analysis and design meta-models (e.g. UML meta-model) should be given to the analyst and designer. Extensions of the generic analysis and design meta-models can be used in the software engineering as guiding framework for analysis and design. Extended analysis meta-model, that embodies domain specific knowledge, guides analyst during the analysis process, and similarly extended design meta-model, that embodies architecture specific knowledge, guides designer during the design process. In the article we will study the problems of combining several meta-model extensions and offer a solution to interoperability of meta-model extensions. Additionally we discuss how the implementation generators can use meta-model extensions.