Extending use case diagrams to support requirements discovery

Requirements discovery is important in the context of system-of-systems because the requirements are not clear at the outset of the project and the future system may bring innovation to users through integration and orchestration. Modelling the existing systems in order to understand the current work practice of domain users is the first step towards requirements elicitation. Use case diagrams can be used for this modelling as they are powerful to express the behaviour of the system in way that all stakeholders can easily understand. However, with the aim of discovering the hidden interaction among humans, systems and data, use case diagrams need to be extended. This paper introduces some extended features of use case diagrams developed in an EU project, which helped project team discover requirements in their three use cases.