author paulson <>
Mon May 23 15:33:24 2016 +0100 (2016-05-23)
changeset 63114 27afe7af7379
parent 51404 90a598019aeb
permissions -rw-r--r--
Lots of new material for multivariate analysis
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    12 <H2>UNITY--Chandy and Misra's UNITY formalism</H2>
    14 <P>The book <EM>Parallel Program Design: A Foundation</EM> by Chandy and Misra
    15 (Addison-Wesley, 1988) presents the UNITY formalism.  UNITY consists of an
    16 abstract programming language of guarded assignments and a calculus for
    17 reasoning about such programs.  Misra's 1994 paper "A Logic for Concurrent
    18 Programming" presents New UNITY, giving more elegant foundations for a more
    19 general class of languages.  In recent work, Chandy and Sanders have proposed
    20 new methods for reasoning about systems composed of many components.
    22 <P>This directory formalizes these new ideas for UNITY.  The Isabelle examples
    23 may seem strange to UNITY traditionalists.  Hand UNITY proofs tend to be
    24 written in the forwards direction, as in informal mathematics, while Isabelle
    25 works best in a backwards (goal-directed) style.  Programs are expressed as
    26 sets of commands, where each command is a relation on states.  Quantification
    27 over commands using [] is easily expressed.  At present, there are no examples
    28 of quantification using ||.
    30 <P>A UNITY assertion denotes the set of programs satisfying it, as
    31 in the propositions-as-types paradigm.  The resulting style is readable if
    32 unconventional.
    34 <P> Safety proofs (invariants) are often proved automatically.  Progress
    35 proofs involving ENSURES can sometimes be proved automatically.  The
    36 level of automation appears to be about the same as in HOL-UNITY by Flemming
    37 Andersen et al.
    39 <P>
    40 The directory <A HREF="Simple/"><CODE>Simple</CODE></A>
    41 presents a few examples, mostly taken from Misra's 1994
    42 paper, involving single programs.
    43 The directory <A HREF="Comp/"><CODE>Comp</CODE></A>
    44 presents examples of proofs involving program composition.
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