1. A structured workflow system, comprising: a first data storage for structured work items, 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; a second data storage for local work items, wherein a local work item is a data object input in response to the operation of the business process and a variance from the business process defined by the business process generator; a workflow engine that processes work items and local work items, 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.