This paper describes the use of executable specifications to ease incremental development, by providing more flexibility regarding the order in which modules are implemented. In this approach, the architect provides a specification for each module in the module architecture view. While specifications must precisely describe the ions among modules, they may abstract some of the functionality. These specifications are executable, and interoperate seamlessly with the module implementations. For incremental development this makes the contents of a release more flexible, makes the order of implementation of modules more flexible, and reduces overall effort by reducing or eliminating the need for stubs, drivers, or temporary prototypes of modules. Our approach uses executable specifications written in AsmL and uses the .NET framework for integrating them with implementations. Key Words incremental development, executable specification, AsmL, software architecture