Validating feature-based specifications

It is argued that specifications should be rigorously validated against requirements. This is useful to build confidence in a specification, and to check a specification after it or the requirements have changed. MUSTARD (Multiple-Use Scenario Test and Refusal Description) is introduced as a means of formulating and formalising validation scenarios. The practical use of MUSTARD on a number of case studies is introduced. The MUSTARD notation is then explained, using examples from Internet Telephony to show how validation scenarios are written. The core MUSTARD constructs are augmented by domain-specific vocabularies that adapt it for different kinds of system. It is seen how MUSTARD can validate specifications written in two standardised formal languages: LOTOS (Language Of Temporal Ordering Specification) and SDL (Specification and Description Language).