A precise model of the behavioral dynamics is a necessary precondition for the development of collaborative environments. In this paper we present a specification framework for collaborative environments. In particular we highlight the interplay of task specifications and domain models. The framework consists of two components: A formal specification language (called CTML) and the tool CTML Editor and Simulator. CTML has a precisely defined syntax and semantics and is designed to model actors, roles, collaborative tasks and their dependency and impact on the domain. The CTML Editor and Simulator is an Eclipse IDE for the interactive creation and simulation of CTML specifications.