"Orchestration describes how web services interact with each other at the message level, including the business logic and execution order of the interactions" [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:
- ProcessorReportManagementService.reserveLandingReportNumbers and .reserveFishTicketNumbers
- ProcessorReportManagementService.submitInitialLandingReport
- ProcessorReportManagementService.submitIfqReports (if IFQ reports are included in this landing)
- ProcessorReportManagementService.submitFinalLandingReport
In practice few transactions are this simple, and there is more involved than simply getting the steps in sequence. For example when submitting an update to an existing report it is necessary to distinguish between updates to existing lines versus insertion of new lines, etc.
In order to support integration with third party systems these details of message sequences and conventions must be explicitly documented and there should be automated test suites available for a number of common transactional processes, including:
- Request for landing report and fish ticket numbers
- Submission of a specified "test" landing report
- Update of a previously submitted landing report with updates, inserts and deletions