Event-B Examples

This page is for listing available example Event-B/Rodin projects.

Year 2009

Real-time controller for a water tank

By Michael Butler.

The draft paper outlines an approach to treating continuous behaviour in Event-B by a discrete approximation. An example of a water tank system is used to illustrate the proposed approach. The archive containts the Event-B development for the water tank system.

UML-B Development of an ATM

By Mar Yah Said, Michael Butler and Colin Snook.

This paper outlines support for refinement of classes and statemachines in UML-B and issustrates these with an Automated Teller Machine (ATM) example. The ATM development is contained in a Rodin archive. It consists of an abstract model focusing on bank account updates. The ATM, pin cards and messaging between ATMs and a bank server are introduced in successive refinements.

MIDAS: A Formally Constructed Virtual Machine

By Steve.

MIDAS (Microprocessor Instruction and Data Abstraction System) is a specification of an Instruction Set Architecture (ISA). It is refined to a usable Virtual Machine (VM) capable of executing binary images compiled from the C language. It was developed to demonstrate a methodology for formal construction of various ISAs in Event-B via a generic model. There are two variants: a stack-based machine and a randomly accessible register array machine. The two variants employ the same instruction codes, the differences being limited to register file behavior.

The archive supplied at the Deploy repository contains: C-coded prototypes of the MIDAS VMs, an Event-B model refinement constructing the same VMs, the B2C Event-B to C auto-generation tool, C compiler/assembler/linkers for the VMs, an example C test suite, and execution environments for running compiled C on the machines.

Development of a Network Topology Discovery Algorithm

By Hoang, Thai Son and Basin, David and Kuruma, Hironobu and Abrial, Jean-Raymond.

This paper and this Rodin development is another version of the Link State Routing Development presented in 2008.

Year 2008

Link State Routing Development

By Hoang, Thai Son and Basin, David and Kuruma, Hironobu and Abrial, Jean-Raymond.

We present a formal development in Event-B of a distributed topology discovery algorithm. Distributed topology discovery is at the core several routing algorithms and is the problem of each node in a network discovering and maintaining information on the network topology. One of the key challenges in developing this algorithm is specifying the problem itself.We provide a specification that includes both safety properties, formalizing invariants that should hold in all system states, and liveness properties that characterize when the system reaches stable states. We specify these by appropriately combining invariants, event refinement, and proofs of event convergence and deadlock freedom. The combination of these features is novel and should be useful for formalizing and developing other kinds of semi-reactive systems, which are systems that react to, but do not modify, their environment.

Modelling and proof of a Tree-structured File System

By Damchoom, Kriangsak and Butler, Michael and Abrial, Jean-Raymond.

We present a verified model of a tree-structured file system which was carried out using Event-B and the Rodin platform. The model is focused on basic functionalities affecting the tree structure including create, copy, delete and move. This work is aimed at constructing a clear and accurate model with all proof obligations discharged. While constructing the model of a file system, we begin with an abstract model of a file system and subsequently refine it by adding more details through refinement steps. We have found that careful formulation of invariants and useful theorems that can be reused for discharging similar proof obligations make models simpler and easier to prove.

Deliverable D8 D10.1 "Teaching Materials"

By Abrial, Jean-Raymond and Hoang, Thai Son and Schmalz, Matthias.

Year 2007

Redevelopment of an Industrial Case Study Using Event-B and Rodin

From Rezazadeh, Abdolbaghi and Butler, Michael and Evans, Neil.

CDIS is a commercial air traffic information system that was developed using formal methods 15 years ago by Praxis, and it is still in operation today. This system is an example of an industrial scale system that has been developed using formal methods. In particular, the functional requirements of the system were specified using VVSL -- a variant of VDM. A subset of the original specification has been chosen to be reconstructed on the Rodin platform based on the new Event-B formalism. The goal of our reconstruction was to overcome three key difficulties of the original formalisation, namely the difficulty of comprehending the original specification, the lack of any mechanical proof of the consistency of the specification and the difficulty of dealing with distribution and atomicity refinement. In this paper we elucidate how a new formal notation and tool can help to overcome these difficulties.