Evolution and Incremental Construction Support via Integrated Programming Environment Mechanisms

The mechanisms described in this paper support a software engineering environment in which the transition from initial design through implementation and into maintenance is a smooth and continuous process. Two new datatypes, Nodule and Octopus, are presented. Nodules are templates containing compiled code and labelled typed locations, and are intended to support the interactive construction and evolution of applications. The major benefit of the Nodules over other systems is that they permit application systems to be generated that are complete, internally consistent and strongly type checked. The Octopus mechanism permits executable application systems to be evolved in situ. Using this mechanism, the information that was available to the application developer is accessible to the maintenance programmer. It also enables components of the application to be evolved or replaced, and reconnected to live data in a type safe manner. When combined into a single system, the Nodule and Octopus datatypes enable a rich collection of information about the structure and state of applications to be maintained and made available to programmers not only during the construction phase, but during the entire lifetime of applications.