The main aim of this monograph is to provide a framework forthe integrated design of object-oriented programs withalgebraic specification techniques. The design methodpursued relies fundamentally on the structuring of systemsbased on the notion of data types. Depending on the level ofabstraction, data types are described in an object-orientedway by algebraic specifications or by machine-executableobject-oriented programs. The treatment involves two mainaspects. First, object-oriented programs have to be relatedby a notion of correctness that models the transition fromspecifications to program implementations. The authorpresents a notion of correctness which relies on the idea ofabstraction functions. Second, in order to obtain anintegrated design environment, a uniform structuring conceptfor object oriented programs and algebraic specificationshas to be provided. Inheritance, subtyping and clientshipare three central notions of object-oriented structuring.Theauthor uses them to develop the kernel of a typedobject- oriented programming language. The monographprovides the formal foundation for a unified framework ofalgebraic specifications and object-oriented programs. Amajor guideline is the development of a design methodsupporting the structured design and reuse of software inthis environment.