The compensation model in BizTalk Server 2004 provides a versatile mechanism for addressing an extensive range of business process scenarios. It is used in situations where some condition arises that invalidates the outcomes of previously completed units of work associated with the same business activity. In these scenarios, it is generally necessary to revisit the completed units of work, inspecting the state of the system as it existed at the completion of each of those stages, and taking appropriate actions to undo the work, undertake appropriate compensatory actions or, at the very least, maintain an audit log and/or provide notifications.