For simple data, workflow parameters will probably be adequate—you might not need to provide a schema. For complex data in a Receive or Reply function, you might require an XML schema. See Using Web Services in FileNet® workflows for examples.
TIP To modify the schema retrieved from a file on the server, select the text and copy it to the clipboard. Enter a new schema name and select the Modify button to add the definition. Then click Specify Value and paste the text into the text box. Note that this does not change the originally referenced schema file located on the workflow system server.