--- a/src/HOL/UNITY/README.html Tue Oct 20 11:16:23 1998 +0200
+++ b/src/HOL/UNITY/README.html Tue Oct 20 11:27:06 1998 +0200
@@ -4,21 +4,24 @@
<H2>UNITY--Chandy and Misra's UNITY formalism</H2>
<P>The book <EM>Parallel Program Design: A Foundation</EM> by Chandy and Misra
-(Addison-Wesley, 1988) presents UNITY, which consists of an abstract
-programming language of guarded assignments and an associated calculus.
-Misra's 1994 paper "A Logic for Concurrent Programming" presents "New UNITY",
-giving more elegant foundations for a more general class of languages.
+(Addison-Wesley, 1988) presents the UNITY formalism. UNITY consists of an
+abstract programming language of guarded assignments and a calculus for
+reasoning about such programs. Misra's 1994 paper "A Logic for Concurrent
+Programming" presents New UNITY, giving more elegant foundations for a more
+general class of languages. In recent work, Chandy and Sanders have proposed
+new methods for reasoning about systems composed of many components.
-<P> This directory is a preliminary formalization of New UNITY. The Isabelle
-examples may not represent the most natural treatment of UNITY style. Hand
-UNITY proofs tend to be written in the forwards direction, as in informal
-mathematics, while Isabelle works best in a backwards (goal-directed) style.
+<P>This directory formalizes these new ideas for UNITY. The Isabelle examples
+may seem strange to UNITY traditionalists. Hand UNITY proofs tend to be
+written in the forwards direction, as in informal mathematics, while Isabelle
+works best in a backwards (goal-directed) style. Programs are expressed as
+sets of commands, where each command is a relation on states. Quantification
+over commands using [] is easily expressed. At present, there are no examples
+of quantification using ||.
-<P>
-The syntax, also, is rather unnatural. Programs are expressed as sets of
-commands, where each command is a relation on states. Quantification over
-commands using [] is easily expressed. At present, there are no examples of
-quantification using ||.
+<P>A UNITY assertion denotes the set of programs satisfying it, as
+in the propositions-as-types paradigm. The resulting style is readable if
+unconventional.
<P>
The directory presents a few small examples, mostly taken from Misra's 1994