 
Summary: MODELS FOR CONCURRENCY
Uri Abraham
Department of Mathematics and Computer Science
BenGurion University, Be'er Sheva, Israel
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Preface
The title ``Models for Concurrency'' indicates that models (in the sense of model
theory) are applied here to the analysis of concurrent protocols, and not that
the diverse paradigms for modeling concurrency are explained.
The dominating tenet in concurrency research today takes the notion of a
state as the basic unit, and uses it to describe systems and processes' behavior.
A state is an assignment of values to a set of variables, and analysis of a system
involves defining this set of variables and determining the rulesofchange that
relate states to their successors. A ``history'' is a sequence of states, possibly
infinite, governed by these rules. Correctness proofs are essentially proofs ``by
induction'', whereby an assertion is proved to hold in each state in a history if it
holds in the initial state and then the rules of change will not falsify it. I find that
decomposing reality as a sequence of states is often inadequate and unnatural
