Elicitation of use cases for product lines

Use Cases can be employed in system requirements engineering to capture requirements from an external point of view. In product line modeling, commonalities and variabilities of a family of systems have to be described. In order to support variability modeling for product lines with Use Cases, extensions and modifications of Use Cases have to be provided. Capturing the variations characterizing the different products is a key issue for product line requirements engineering. This paper describes an approach to derive product line requirements in the form of Use Cases, starting from the analysis of user documentations of existing systems. We provide a disciplined approach to integrate legacy information found in existing documentation into product line Use Cases and illustrate this with an example.