As Antony has suggested the custom scenario provider is the way to go. I built a demo a few years ago using that code as a starting point to extract the data from the Decision Warehouse to use as a Test Suite and also Simulations. I seem to recall that the XML format extracted is not in the same format that is required for input to a rule service so you need to manipulate it first. Originally I was creating clean XML from it but more recently I was generating a JSON payload from it. It was a demo so the data was flat and not very complex so it did not take long to generate the JSON with a few simple REGEX expressions and a long string concatenation.