Interactive system design requires good descriptive systems, and the development of tools to support it. In particular, models and notations are required for describing user tasks, and for describing the structure of the human-computer dialogue to support these tasks. These descriptions should ideally be linked. This paper reviews task and dialogue models, and describes how the divide between the two can be bridged via the Lean Cuisine+ notation. The notation is placed in a wider context by reference to the system development life cycle and the unified modeling language (UML).