Efficient organizations need to ensure that their business processes are flexible so that these processes can easily accommodate changes in regulations and policies. Appropriate techniques to model and verify these processes are required. In this paper, the authors present a rule-based approach, which is built upon the Event-Condition-Action model (ECA) and supported by a Rule-based Business Process Definition Language (RbBPDL). In this approach, rules, which specify business processes, are represented using the Event-Condition-Action-Post-condition-Event (ECAPE) model. This allows translating a process into a graph of rules that is used to check how flexible a business process is, and estimating this process's cost of changes.