The system specification support environment presented in this paper, PROSPEX (Product Specification Expert), supports the RT-SA methodology. It not only provides graphic support for drawing, but also helps the engineer in the analysis and design process itself. PROSPEX analyses the quality and correctness of the RT-SA diagrams using knowledge-based techniques. PROSPEX also includes features for supporting design reuse. The development environment of PROSPEX was KEE expert system development shell running on a Symbolics workstation!. Keywords