What are the three types of abstract system model that are recommended by the MDA method?

What are the three types of abstract system model that are recommended by the MDA method?
Answer: 1. A computation independent model (CIM) that models the important domain abstractions used in the system. CIMs are sometimes called domain models. You may develop several different CIMs, reflecting different views of the system.
2. A platform independent model (PIM) that models the operation of the system without reference to its implementation. The PIM is usually described using UML models that show the static system structure and how it responds to external and internal events.
3. Platform specific models (PSM) which are transformations of the platform independent model with a separate PSM for each application platform.