I am reading a technical standard IEEE 730-2014 which defines the following two activities:
5.4.3 Evaluate product for conformance to established requirements Determine the degree to which the software products and related documentation conform to established requirements.
5.4.4 Evaluate product for acceptability Prior to delivery, determine the degree of confidence the supplier has that the established requirements are satisfied and that the software products and related documentation will be acceptable to the acquirer. Collect measurement data sufficient to support these satisfaction and acceptability decisions. A contract may provide that the acquirer, prior to delivery, determine whether software products are acceptable.
Why either alone is not enough? (it is a topic for discussion in a book that describe this standard). I mean - when I meet all contractual requirements (even when the customer wrote them wrong), I did my part and met the contractual requirements. What is then meant by this acceptability evaluation and how does it work in practice?