On-site customer in an XP project: empirical results from a case study

Extreme programming (XP), similarly to other agile software development methods, values close collaboration with customers. One of the XP practices suggests that the customer should be 100% available for the development team. Anecdotal evidence suggests that the XP customer role is costly, difficult and demanding. However, very few empirical studies have been published on the role of customer in an XP project. The results of this controlled case study are in line with the common belief that the on-site customers role is indeed demanding, requiring a strong ability to resolve issues rapidly. Yet, the study also offers contrasting findings in terms of required actual customer involvement in the development project. This empirical case demonstrates that while the customer was present close to 100% with the development team, only 21% of his work effort was required to assist the team in the development. However, it is also shown that an on-site customer may create a false sense of confidence in the system under development. The implications of these and other findings are discussed.