The Isabelle/Isar Implementation

We describe the key concepts underlying the Isabelle/Isar implementation, including ML references for the most important functions. The aim is to give some insight into the overall system architecture, and provide clues on implementing applications within this framework. Isabelle was not designed; it evolved. Not everyone likes this idea. Specification experts rightly abhor trial-and-error programming. They suggest that no one should write a program without first writing a complete formal specification. But university departments are not software houses. Programs like Isabelle are not products: when they have served their purpose, they are discarded. Lawrence C. Paulson, “Isabelle: The Next 700 Theorem Provers” As I did 20 years ago, I still fervently believe that the only way to make software secure, reliable, and fast is to make it small. Fight features. Andrew S. Tanenbaum One thing that UNIX does not need is more features. It is successful in part because it has a small number of good ideas that work well together. Merely adding features does not make it easier for users to do things — it just makes the manual thicker. The right solution in the right place is always more effective than haphazard hacking. Rob Pike and Brian W. Kernighan If you look at software today, through the lens of the history of engineering, it’s certainly engineering of a sort–but it’s the kind of engineering that people without the concept of the arch did. Most software today is very much like an Egyptian pyramid with millions of bricks piled on top of each other, with no structural integrity, but just done by brute force and thousands of slaves. Alan Kay