Orchestration describes how web services interact with each other at the message level, including the business logic and execution order of the interactions 1[Chris Peltz 2003]. These interactions may span applications and/or organizations, and result in a longlived, transactional, multi-step process model. For example, in the eLandings web services interface, the simplest case of reporting a landing requires a minimum of the following web service method invocations:
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