The seven key principles of correct by construction

The seven key principles of correct by construction:

1. Expect requirements to change.
2. Know why you're testing.
3. Eliminate errors before testing.
4. Write software that is easy to verify.
5. Develop incrementally.
6. Some aspects of software development are just plain hard.
7. Software is not useful by itself.

a. "To allow the developers to get from a set of requirements to an implementation.
b. "To allow the maintainers to understand how the implementation satisfies the requirements."