Introducing contracting in distributed transactional workflows

We describe a flexible transactional workflow environment based on an extensible object-oriented framework built around class libraries, application programming interfaces, and shared services. To enforce coordination in workflow communications and model real-life business applications, the concepts of 'obligation' and 'contract' are introduced. A contract is a semantic agreement between two or more collaborating workflows in terms of a protocol-oriented specification of obligations. It is used to describe the communication between systems by means of nested transactions associated with the provision of services. An example from the banking world illustrates this approach.