Efficient organizations need to ensure that their business processes are at the same time robust and agile. These two features could be verified using appropriate techniques. In this paper, the authors present a new rule based model for the business process flexibility management and verification. To achieve these two objectives, the new model is grounded on a new formalism issued from ECA model and supported by a language called RbBPDL (Rules based Business Process Definition Language). In this model, a business rule has an Event-Condition-Action-Post condition-Event triggered (ECAPE) formalism.