An interactive computer system is a computational system designed to engage users by providing real-time feedback in response to user inputs. Numerous studies have shown the importance of placing humans (e.g., end users or application clients) at the center of the design of this kind of system, which has led to the emergence of agile and human-computer interaction approaches. However, typical software development processes remain highly functionality-focused, making it difficult to integrate human-computer interaction processes. This chapter investigates the integration of approaches coming from these two distinct communities in the development process by examining the activities required to bridge their domains.