3,537 research outputs found
Refinement Calculus of Reactive Systems
Refinement calculus is a powerful and expressive tool for reasoning about
sequential programs in a compositional manner. In this paper we present an
extension of refinement calculus for reactive systems. Refinement calculus is
based on monotonic predicate transformers, which transform sets of post-states
into sets of pre-states. To model reactive systems, we introduce monotonic
property transformers, which transform sets of output traces into sets of input
traces. We show how to model in this semantics refinement, sequential
composition, demonic choice, and other semantic operations on reactive systems.
We use primarily higher order logic to express our results, but we also show
how property transformers can be defined using other formalisms more amenable
to automation, such as linear temporal logic (suitable for specifications) and
symbolic transition systems (suitable for implementations). Finally, we show
how this framework generalizes previous work on relational interfaces so as to
be able to express systems with infinite behaviors and liveness properties
Weakest Preconditions for Progress
Predicate transformers that map the postcondition and all intermediate conditions of a command to a precondition are introduced. They can be used to specify certain progress properties of sequential programs
An expectation transformer approach to predicate abstraction and data independence for probabilistic programs
In this paper we revisit the well-known technique of predicate abstraction to
characterise performance attributes of system models incorporating probability.
We recast the theory using expectation transformers, and identify transformer
properties which correspond to abstractions that yield nevertheless exact bound
on the performance of infinite state probabilistic systems. In addition, we
extend the developed technique to the special case of "data independent"
programs incorporating probability. Finally, we demonstrate the subtleness of
the extended technique by using the PRISM model checking tool to analyse an
infinite state protocol, obtaining exact bounds on its performance
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