Business process management systems (BPMS) are designed to automate routine procedures. They are consequently less supportive of knowledge intensive work, which is neither repetitive nor prescribed in detail. Instead, plans are elaborated and reinterpreted as the work progresses. Interactive process models are created and updated by those that manage and perform the work, in order to reflect such evolving plans. These models directly control the behaviour of the IT system. The challenges that such an interactive system must meet include (1) to enable modelling by end users, (2) to integrate ad-hoc and structured work, (3) to dynamically customise services and interfaces, and (4) to anchor knowledge management in everyday work. This book presents the WORKWARE system and modelling framework, which apply techniques such as interactive model execution, semantic holism and instance orientation to meet these challenges. Prototype implementation, experimental use and comparison with related work show that the design is feasible, useful and novel.