The author provides an account of formal specification in an industrial setting. The volume takes a particular approach to the semantics of specification languages: the understanding that the meaning of specifications can be taken as presentations of logical theories is fundamental to that approach. An extension of the specification language VDM-SL is introduced and the formal semantics of VVSL are presented. The practical use of this language is further demonstrated by two detailed case studies which provide a comprehensive picture of the relational approach to databases and are essential reading for those employing formal specifications in software development.