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An Architectural Description of the Simplex Architecture

March 1996 Technical Report
JoseGermanRivera, AlejandroAndresDanylyszyn, Charles B. Weinstock, Lui R. Sha, Michael J. Gagliardi

This report describes SEI-developed Simplex, a software architecture for dependable and evolvable process-control systems.


Software Engineering Institute

CMU/SEI Report Number



Simplex is a software architecture for dependable and evolvable process-control systems developed by the Software Engineering Institute. Our project consisted of creating a formal specification of this architecture, and analyzing its safety and liveness properties. We developed a Communicating Sequential Processes (CSP) model to describe the overall dynamic behavior of the Simplex architecture, which we verified using the Failure-Divergence Refinement (FDR) model checker. As a result, we discovered interesting things about the use of FDR that revealed subtle points in the Simplex architecture. We also developed a WRIGHT specification of this architecture to characterize precisely the connections between its components at the architectural level. The specification was based on the latest version of the CSP model.