1 Formal Development of Broadcast Systems and Verification of Ordering Properties using Event-B Divakar Yadav and Michael Butler Divakar Yadav is Assistant Professor of Computer Science at Institute of Engineering and Technology, Lucknow, India. This research was carried out at Dependable Systems and Software Engineering Research group, School of Electronics and Computer Science, University of Southampton as a Commonwealth Scholar supported by the Commonwealth Scholarship Commission in the United Kingdom. Michael Butler is Professor of Computer Science at Dependable Systems and Software Engineering research group, School of Electronics and Computer Science, University of Southampton, UK. Michael Butler’s contribution is part of the EU ICT project 214158 DEPLOY (Industrial deployment of system engineering methods providing high dependability and productivity) www.deploy-project.eu. September 18, 2008 DRAFT