Abstract
When performing functional requirements analysis, software developers need to understand the application domain to fulfil organizational needs. This is essential for making trade-off decisions and achieving the success of the software development project. An application domain is dealt within the modelling phase of the business process lifecycle. Assuming that functional changes are inevitable, we propose to use the standard COSMIC to evaluate these changes and provide indicators of change status in the business domain. Expressing functional changes in terms of COSMIC Function Point units can be helpful in identifying changes leading to potential impact on the business process's functional size. In addition, we propose a top-down decomposition approach to specify requirements and analyse change impact on BPMN models at different abstraction levels.