S-Type Systems  

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S-Type Systems


Reference /Lehman, 1985a/ Software Evolution - Processes of Software Change
/Lehman, 2000b/ Rules and Tools for Software Evolution and Management
In S-type programs the sole criterion of acceptability is correctness in the mathematical sense. Continuing change and growth, and hence, evolution over a series of versions or releases, appear to be inherent properties of E-type systems, and hence the importance of their study and of the laws that apply to them. S-type systems have their role, for example, as building blocks from which E-type systems are from.
Reference William Aspray interviews M. M. Lehmann
S-type programs are programs where the criterion of success is that the program satisfies its specification. This is a mathematical concept, and in my view the relevance of Dijkstra's approach is restricted to S-type programs.
For such programs one's obligations are restricted to a demonstration that the program is correct relative to the specification. It says nothing at all about the specification. The criterion of success in creating an S-type program is that it is correct in a strict mathematical sense.

See also

Glossary E-Type Systems

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