DUAL: An Interactive Tool for Developing Documented Programs by Step-Wise Refinements

Programs are integrated hierarchical structures of formal texts - instructions - and informal texts - documentation. Only if there is a mechanical connection between program design and program development there can be higher chances that the program documentation, originated at design time, will not, sooner or later, become obsolete with respect to the current state of the system. DUAL is an interactive, incremental, intelligent editor of program and documentation texts to be used for software implementations whose anticipated life cycle is significantly long to deserve much attention. The screen interface plays a unique role in DUAL since it allows a visitor ( designer or maintenance engineer) “to replay” as many times as desired the evolution of the system from design to implementation. The access to the hierarchically organized Design Information is made easy and natural by the DUAL video oriented user interface.