Use cases versus task descriptions

Abstract. [Context and motivation] Use cases are widely used as a substantial part of requirements, also when little programming is expected (COTS-based systems). [Question/problem] Are use cases effective as requirements? To an-swer this question, we invited professionals and researchers to specify require-ments for the same project: Acquire a new system to support a hotline. [Princi-pal ideas/results] Among the 15 replies, eight used traditional use cases that specified a dialog between users and system. Seven used a related technique, task description, which specified the customer's needs without specifying a dialog. [Contribution] It turned out that the traditional use cases covered the customer's needs poorly in areas where improvement was important but diffi-cult. Use cases also restricted the solution space severely. Tasks didn't have these problems and allowed an easy comparison of solutions.