A large number of problems to be solved with the help of computer systems are ill-structured. Their solution requires incremental design processes, because complete and stable specifications are net available.For tasks of this sort, life cycle models are inadequate. Our design methodology is based on a rapid prototyping approach which supports the coevolution of specification and implementation. Communication between customers, designers and implementors and communication between the humans and the knowledge base in which the emerging product is embedded are of crucial importance. Our work is centered around knowledge-based systems which enhance and support the communication needs in connection with software systems.Program documentation systems are used as an example to illustrate the relevance of knowledge-based human-computer communication in software engineering.