1School of Computing

Like any other quality attribute, usability cannot be achieved at the last development moment. On the contrary, usability has to be taken into account right from the earliest stages by considering features that raise the usability level of the software system as well as usability requirements that enhance the performance of other functional requirements. However, existing HCI usability heuristics are not sufficient to serve as proper requirements from a software engineering perspective. HCI heuristics for incorporating usability features lead to incomplete and ambiguous requirements. For example, the classical approach for reducing requirements ambiguity, related to incorporating new information, cannot be used for usability requirements, since the information that would need to be added is likely to be beyond the usability knowledge of most requirements writers, developers and users. One possible solution to this problem is to bring HCI experts into the software development process. However, this is not a straightforward approach and may have serious implications for the development process. In this paper, we propose an alternative solution based on the definition of usability elicitation patterns. These patterns capitalise upon the know-how in usability requirements elicitation by specifying fundamental elements recurrently intervening in usability requirements elicitation. We have focused on usability features with major implications in functionality