You want to create expense reports (Business Object ERM_EXPENSE_REPORT) via a Web Service created with PDI.
SAP Business ByDesign
Cloud for Travel & Expense
This is a Complex field control logic and doesn't support creation of expense reports via Web Service.
Functionality is not supported.
This is also the reason why there is no Standard Web Service for Expense Reports
Note: Currently its not possible to create Expense Reports using OData. The functionality to create expense reports is such complex that it does not allow creation through OData Services.
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