IntroductionRecently, the field of computer science has acknowledged the idea that findings from the domains of psychology and sociology matter to the design of group systems. The design of group systems that support Computer Supported Collaborative Learning (CSCL) and Working (CSCW) integrates knowledge of how people work and learn in groups with knowledge of enabling technologies (Preece, 2000, Schümmer & Lukosch, 2007Wilson, 1991). This had led to several requirements for task-related functionality, such as facilities for communication, file-sharing, calendaring and scheduling (Vick, 1998). However, there are other, often less-obvious requirements.These relate to the support of psychological and social processes, which impact group cohesion and team performance, such as group dynamics and people's perceptions of each other. These processes have traditionally been studied in social sciences. As they are essential corner stones for team performance and interaction, they are thus also relevant for team performance in mediated environments. Indeed, according to Ackerman (2000), the main problem in group systems nowadays is the discrepancy between the social needs and expectations of the user and the computer system functionality.Although 'social informatics' (Grudin, 1994;Kling, 1999;Preece, 2000) acknowledge the relevance of findings from the social sciences for the design of group systems, this does not guarantee their systematical incorporation in the actual practice of systems design. Kling (1999) notices that such findings are 'scattered in the journals of several different fields' (p.1), which makes it hard to locate important studies. Moreover, system designers usually don't have enough time to orient themselves in domains which might contain parts and ideas which are useful (Erickson, 1997).To overcome knowledge transfer and time problems the notion of 'design patterns' was introduced into the field of computer science; it was meant to enhance interdisciplinary 2 communication and foster re-use of effective concepts (Borchers, 2003;Erickson, 2000). Design patterns provide a systematic, action-and design-oriented approach to incorporate findings from sociology and psychology in the design of computer systems. A pattern is a 'description of a problem which occurs over and over again in our environment, and then describes the core of the solution to that problem, in such a way that you can use this solution a million times over ' (Alexander, 1977).The strength of a design pattern is that it captures the essence of a "problem -solution"-dyad in a specific context, and presents it in such a way that it can be applied and adapted in different settings (Erickson, 2000;Dearden, Finlay, Allgar & McManus, 2002;Goodyear, 2005).Design patterns for collaborative environments have been developed in several projects, such as E-LEN (2004), Patterns4Groupware (Schümmer, Fernandez, & Holmer, 2002;Schümmer & Lukosch, 2007) and the project that created the COLLAGE platform (Hernández-Leo et al., 2006).The development of a...