Abstract: In this paper we study the qualification problem in theories of reasoning about actions and change and the link of this problem to properties of representation for expressing such theories. We examine the interaction of the qualification problem with the frame and ramification problems and show how an integrated solution to these problems can be developed where the frame persistence and constraint satisfaction qualify implicitly the action effect laws of the theory. We compare the two approaches of implicit and explicit qualification of the effects laws and argue that from the point of view of knowledge representation the former has better properties pertaining to elaboration tolerance.