FDR Explorer

Abstract

We describe: (1) the internal structures of FDR, the refinement model checker for Hoare's Communicating Sequential Processes (CSP); and (2) an application-programming interface (API) that allows users to interact more closely with FDR and to have finer-grain control over its behaviour and data structures. This API makes it possible to create optimised CSP code to perform refinement checks that are more space or time efficient, enabling the analysis of more complex and data-intensive specifications. The API can be used either by those constructing CSP models or by tools that automatically generate CSP code. We present examples of using our tool, including handling advanced FDR features such as transparent functions, which compress state spaces before checking. We also show how to transform FDR's graph format into a graph notation such as JGraph, enabling visualisation of labelled transition systems of CSP specifications.

On the Cloud-Enabled Refinement Checking of Railway Signalling Interlockings

“…An experimental parallel implementation of FDR is described in [22]: states are randomly allocated between different computing nodes using a hash function; the state space is explored using a breadth-first search algorithm, and at the end of each level successor states are exchanged between the compute nodes. An alternative approach is that taken by FDR Explorer [23], whereby an API "makes possible to create optimised CSP code to perform refinement checks that are more space or time efficient, enabling the analysis of more complex and data-intensive specifications." Our approach involves partitioning the problem not at the level of the state space, but at the level of the CSP model -which means it is applicable only in certain scenarios, with one being the contribution of [19].…”

Concurrent Models of Flash Memory Device Behaviour

“…To succeed, some creativity will be required, since the CSP model (as it currently stands) runs into the resource limits of the FDR2 model-checker. One possible approach will be to use FDR Explorer [FW09] to assist us.…”