Event Ordering Using Graphical Notation for Event-B Models

System requirements are sometimes either too complex or undefined. Event-B is a formal modeling method and is being used increasingly to model various systems. Event-B models support atomicity decomposition and are quite useful for complex refinement structures. However, neither a Event-B model represents any explicit control flows among the events, nor does it support links between the new events during refinements. This work aims to model the Stop and Wait mechanism for an Automatic Repeat Request (ARQ) protocol to analyze the complexities due to communication errors during data re-transmissions. The limitation is the lack of control flows among the events during successive refinements. This has been graphically represented in this work and embedded with Event-B notations for the atomicity decomposition of the model. Finally, the successive refinements presented using an Event-B model, has been validated using the Rodin tool. This leads to a successful ARQ model.