A First Attempt to Express KAOS Refinement Patterns with Event B

Abstract

It is now recognised that goals play an important role in requirements engineering process, and consequently in systems development process.Whereas specifications allow us to answer the question”WHAT the system does”, goals allow us to address the ”WHY, WHO, WHEN” questions [1]. Up to now, the development process associated with formal methods, including Event B, begins at the specification level. Our objective is to include requirements analysis within this process, and more precisely KAOS[2] which is a methodology to implement goal-based reasoning. Existing work [3,4] that combine KAOS with formal methods generate a formal specification model from a KAOS requirements model.We aim at expressing KAOS goal models with a formal language (Event B), hence staying at the same abstraction level. Our work is based on a constructive approach in which Event B models are built incrementally from KAOS goal models, driven by goal refinement patterns [1]. Since a KAOS goal means that a property must be established, the main idea is to represent each goal as a B event and the property as the post-condition of this B event. Up to now, we consider refinement patterns defined with first-order logic. Patterns with LTL temporal logic will be studied in further work.