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vienna[w85,jmc]		Modifying programs without reading them

For conference in honor of Heinz Zemanek

elephant, abstract actions
reference to past and future
programming in external language
as few as possible internal variables and data structures

What does natural language have that programming languages don't
have and need?  Very little, if any, of it is syntactic.

need another example besides reservation system

The abstract action program can serve as a specification, but
then the proof of correctness must identify events in the
operation of the program with the abstract actions of the
specification.