This paper describes an approach to adapt the use-case point estimation method to lit the requirements of agile development of interactive software. Creating product cost estimates early in the development lifecycle is a challenge for the software industry, they require substantial data from past projects and constant feedback and fine-tuning, which are rarely available or consistent through interactive software development. In addition, the profusion of incremental and evolutionary development methods (like Scrum and XP) produced new challenges with estimating frequent releases. Here we propose several changes to the original use-case point estimation method, in particular to take advantage of the enhanced information that can be extracted from usage-centered design (usageCD) that devotes particular attention to critical aspects like weighting actors and uses-cases for complexity. We propose to exploit user-roles, essential use-cases and the usageCD architecture to enhance the weighting heuristics for assigning complexity factors to actors and use-cases required to calculate the unadjusted use-case point reflecting the complexity of the requirements for a given iteration or evolution. We propose to exploit user-roles as the main basis for weighting complex actors, which originally are grouped in the highest weight factor. Conversely we propose to extract the complexity of use-cases from essential use case steps depicted through user intentions and system responsibilities and also the analysis classes extract from those for the usageCD architecture. Detailing this approach the paper presents a contribution, not only to leverage more accurate early lifecycle software estimation, but also to bridge the gap between SE and HCI enabling cross-fertilization between the two disciplines.
