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(* Title: HOL/UNITY/UNITY
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ID: $Id$
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Author: Lawrence C Paulson, Cambridge University Computer Laboratory
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Copyright 1998 University of Cambridge
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The basic UNITY theory (revised version, based upon the "co" operator)
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From Misra, "A Logic for Concurrent Programming", 1994
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*)
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UNITY = Traces + Prefix +
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constdefs
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constrains :: "['a set, 'a set] => 'a program set"
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"constrains A B == {F. ALL act: Acts F. act^^A <= B}"
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stable :: "'a set => 'a program set"
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"stable A == constrains A A"
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strongest_rhs :: "['a program, 'a set] => 'a set"
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"strongest_rhs F A == Inter {B. F : constrains A B}"
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unless :: "['a set, 'a set] => 'a program set"
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"unless A B == constrains (A-B) (A Un B)"
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invariant :: "'a set => 'a program set"
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"invariant A == {F. Init F <= A} Int stable A"
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(*Polymorphic in both states and the meaning of <= *)
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increasing :: "['a => 'b::{ord}] => 'a program set"
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"increasing f == INT z. stable {s. z <= f s}"
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end
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