header {* \chapter{The Rely-Guarantee Method}
\section {Abstract Syntax}
*}
theory RG_Com imports Main begin
text {* Semantics of assertions and boolean expressions (bexp) as sets
of states. Syntax of commands @{text com} and parallel commands
@{text par_com}. *}
type_synonym 'a bexp = "'a set"
datatype 'a com =
Basic "'a \<Rightarrow>'a"
| Seq "'a com" "'a com"
| Cond "'a bexp" "'a com" "'a com"
| While "'a bexp" "'a com"
| Await "'a bexp" "'a com"
type_synonym 'a par_com = "'a com option list"
end