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(* Title: ZF/UNITY/Comp.thy
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ID: $Id$
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Author: Sidi O Ehmety, Computer Laboratory
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Copyright 1998 University of Cambridge
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Composition
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From Chandy and Sanders, "Reasoning About Program Composition",
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Technical Report 2000-003, University of Florida, 2000.
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Revised by Sidi Ehmety on January 2001
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Added: a strong form of the order relation over component and localize
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Theory ported from HOL.
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*)
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Comp = Union +
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constdefs
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component :: [i, i] => o (infixl 65)
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"F component H == (EX G. F Join G = H)"
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strict_component :: [i, i] => o (infixl "strict'_component" 65)
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"F strict_component H == F component H & F~=H"
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(* A stronger form of the component relation *)
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component_of :: "[i,i]=>o" (infixl "component'_of" 65)
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"F component_of H == (EX G. F ok G & F Join G = H)"
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strict_component_of :: "[i,i]=>o" (infixl "strict'_component'_of" 65)
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"F strict_component_of H == F component_of H & F~=H"
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(* Preserves a state function f, in particular a variable *)
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preserves :: (i=>i)=>i
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"preserves(f) == {F:program. ALL z. F: stable({s:state. f(s) = z})}"
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localize :: "[i=>i, i] => i"
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"localize(f,F) == mk_program(Init(F), Acts(F),
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AllowedActs(F) Int (UN G:preserves(f). Acts(G)))"
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end
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