1. In a workflow server that implements a structured workflow system, a computer-implemented method of controlling the workflow server, comprising: storing structured work items in a first data storage, wherein each work item is a data object representing a task to be performed by an actor, wherein an actor is one or more of a person, a group of persons and a machine, the structured work items being defined for a business process by a business process generator; storing local work items in a second data storage, wherein a local work item is a data object input in response to the operation of the business process and in response to a variance from the business process defined by the business process generator; processing work items and local work items by a workflow engine, including processing links between at least one work item and one local work item such that constraints on the business process set by the business process generator are followed in processing local work items, wherein the actor is assigned a first set of permissions representing security constraints on modifying and/or accessing elements of the first data storage, wherein an operator of the business process generator is assigned a second set of permissions, and wherein the second set of permissions includes at least one permission not included in the first set of permissions, wherein the business process includes a first phase and a second phase, wherein the second phase follows the first phase, wherein each of the work items and the structured work items is in one of the first phase and the second phase, and wherein the constraints on the business process are defineable by the actor to move a designated work item from the first phase to the second phase.