Correctness is clearly the prime quality. If a system does not do what it is supposed to do, then everything else about it matters little.
French academic, author, and consultant in the field of computer languages. Created Eiffel and the idea of design by contract. Also defined the Uniform Access Principle. Received the Software System Award of the ACM for "impact on software quality" in recognition of the design of Eiffel. Fellow of the ACM since 2008.