Reasoning about interactive system

Interactive systems have goals and characteristics that differ from those of batch systems. These differences lead to a need for new techniques, methods, and tools for manipulating and constructing interactive systems. The difference in structure between batch and interactive systems. The difference is considered, focusing on the distinction between command decomposition and component decomposition. The possible ways of solving a problem using an interactive system using action paths, which account for the relatively unconstrained actions of interactive users, are described. It is shown that interactivity is not an inherent characteristic of a system but rather a characteristic that depends on the error profile of its users. The requirements that interaction places on the underlying implementation, specifically the need for incrementality and integration, are considered. The results are applied to several existing classes of systems