TLZ

A Z schema can specify a functional system—one that produces an output in response to an input. For example, a simple text editor is a functional system; it can be specified by a Z schema that describes the effect of each keystroke on the screen. A reactive system interacts with its environment in a more complex fashion. Adding an interrupt key, which allows the user to stop a long operation before it completes, turns a simple text editor into a reactive system. Concurrent and distributed systems are usually best viewed as reactive systems. Z by itself is inadequate for specifying reactive systems.

Authors and Affiliations

1. Digital Systems Research Center, 130 Lytton Avenue, Palo Alto, California, 94301, USA

   Leslie Lamport

Editors and Affiliations

1. Programming Research Group, Oxford University Computing Laboratory, Wolfson Buliding, Parks Road, OX1 3QD, Oxford, UK

   J. P. Bowen MA

2. Praxis Systems plc, 20 Manvers Street, BA1 1PX, Bath, UK

   J. A. Hall MA, DPhil, CEng

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© 1994 British Computer Society

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