Graphical Configuration Programming: The Structural Description, Construction and Evolution of Software Systems Using Graphics

In systems engineering, considerable advantages accrue by constructing and managing the system in terms of its software configuration; that is the set of constituent software components together with their control and communication interconnections. A specification of the system configuration can be used both to describe the required system structure and for actual system construction. Management of the operational system is achieved by monitoring the status of components and making extensions or changes to that system configuration by the addition of software components or the replacement of existing ones. The performance of these programming tasks at the configuration level is termed configuration programming. Configuration descriptions and changes are most easily described and viewed graphically, but have traditionally been provided to the system in textual form. This paper describes a graphical workstation which integrates the textual and graphical information required for configuration programming. It provides editing facilities for drawing and describing system configurations; monitoring facilities for viewing the current system configuration, component status and interconnections; layout facilities for automatically generating the graphic representations from text and improving the configuration information layout, and control facilities to permit system changes to be initiated by graphical changes to the system configuration. In contrast to many system construction tools, changes are applied dynamically to operational systems. The paper discusses the issues raised by graphical configuration programming, describes the workstation in more detail and presents examples and experience using the approach in Conic, an environment for programming and managing distributed and concurrent systems.