End-user modifiability in design environments

Convivial systems encourage users to be actively engaged in generating creative extensions to the artifacts given to them. Convivial systems have the potential to break down the counterproductive barrier between programming and using programs. Knowledge-based design environments are prototypes for convivial systems. These environments support human problem-domain communication, letting users work within their domains of expertise. One of the design rationales behind design environments is to ease the construction and modification of artifacts designed within the environment. But because design environments are intentionally not general purpose programming environments, situations will arise that require modifications to the design environment itself. The rationale and the techniques for these later modifications are discussed in this paper. Our conceptual framework for end-user modifiability is illustrated in the context of JANUS, an environment for architectural design. Evaluating our system building efforts against our objectives shows the subtleties of integrating end-user modifiability in these kinds of systems.