Traditional projects fix the scope and establish a budget. With these as non-negotiable constraints, project control efforts concentrate on time management. Agile projects target a deadline for a proportionate cost. The effort switches to managing the scope and making sure that all of the most important functionality is delivered before an agreed date. The usefulness and usability of each function is constantly being assessed. This requirs a great deal of cooperation between the customer and the development team that revolves around managed prototypes and facilitated workshops.