Key extensions of abstract data types, final algebras, and database semantics

  • H. -D. Ehrich
Part II Research Contributions Section 2: Specification
Part of the Lecture Notes in Computer Science book series (LNCS, volume 240)


The algebraic specification of abstract data types provides a number of features for structuring specifications in order to make them easier to write, to read, to understand, and to maintain. Among the most important such features are different kinds of extensions, based on initial, final, or behavioural semantics. This paper studies a new kind of extension called key extension, and its final algebra semantics. Key extensions model one of the essential steps in database specification where abstract object types are to be specified on the basis of given abstract data types. The intended standard semantics is a universe of "possible objects" that provides the basis for further database concepts like situations, states, etc. It is shown under which conditions final algebras exist that can serve as a natural standard semantics for key extensions. We also characterize rather a large class of constraints that can be used for keys in accordance with our semantics.


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Copyright information

© Springer-Verlag Berlin Heidelberg 1986

Authors and Affiliations

  • H. -D. Ehrich
    • 1
  1. 1.Inst. f. Informatik, TU BraunschweigBraunschweigWest Germany

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