Abstract. Traditional work ow systems focus on providing support for the control- ow perspective of a business process, with other aspects such as data management and work distribution receiving markedly less attention. A guide to desirable work ow characteristics is provided by the well-known work ow patterns which are derived from a comprehensive survey of contemporary tools and modelling formalisms. In this paper we describe the approach taken to designing the newYAWL work ow system, an o ering that aims to provide comprehensive support for the control- ow, data and resource perspectives based on the work ow patterns. The semantics of the newYAWL work ow language are based on Coloured Petri Nets thus facilitating the direct enactment and analysis of processes described in terms of newYAWL language constructs. As part of this discussion, we explain how the operational semantics for each of the language elements are embodied in the newYAWL system and indicate the facilities required to support them in an operational environment. We also review the experiences associated with developing a complete operational design for an o ering of this scale using formal techniques. 1