WSDL files define operations that receive an input message and, optionally, return an output message and a fault message. In the Participants or Interfaces view, you can add sample data values for message parts. When you are ready to test your process, you can load the sample message part values into your variables to simulate the actual messages exchanged by Web services. As you execute and debug your process, you can inspect the input, output, and fault data values as they are processed.
By adding sample data values to WSDL messages, you have a default set of data across all projects. The Project Explorer keeps track of all sample files and their locations and presents them to you when you are loading values into message variables.