On the Definition of Architecture, Design and Implementation

The terms architecture, design, and implementation are typically used informally in partitioning software specifications into three coarse strata of abstraction. But these strata are not well-defined in either research or practice and often overlap causing confusion and needless discussion. To remedy this problem we formally define two criteria: the Intension and the Locality Criteria, and show that the intuitive discrimination between the three terms architecture, design, and implementation is qualitative and not merely quantitative. We demonstrate that architectural styles are intensional and non-local; that design patterns are intensional and local; and that implementations are extensional and local