Information technology has been used in organisational settings and for organisational purposes such as accounting, for a half century, but IT is now increasingly being used for the purposes of mediating and regulating complex activities in which multiple professional users are involved, such as in factories, hospitals, architectural offices, and so on. The economic importance of such coordination systems is enormous but their design often inadequate. The problem is that our understanding of the coordinative practices for which these systems are developed is deficient, leaving systems developers and software engineers to base their designs on commonsensical requirements analyses. The research reflected in this book addresses these very problems. It is a collection of articles which establish a conceptual foundation for the research area of Computer-Supported Cooperative Work.