Lehman's Categories of Software Systems

A lightning talk presented at SPA 2017

Transcript

3. … any program is a model of a model within a theory of a model of an abstraction of some portion of the world or of some universe of discourse. –Manny Lehman Programs, Life Cycles, and Laws of Evolution. 1980
4. Lehman's categories of software system S-type formally defined by and derivable from a specification P-type solves a real-world problem but does not affect the world it models E-type embedded in the world it models; its operation changes that world
5. E-type Systems
6. Deploying the system changes what it must do
7. The system is only useful if you can change what it does
8. The way you change the system is part of the system
9. The tests of the system are part of the system
10. The people who change the system are part of the system
11. The system is part of the organisational system that directs its evolution
12. Changing how the organisation delivers the system is a delivery of the system
13. Norbert Wiener, "father of cybernetics"