My exact case was some reporting for some project (15 people, 36 months, 1 xml per person per month), to throw into excell and draw one graph, for one PPT, a one time deal, for one project manager to show the numbers on the report.

The end project, if I didn't stop the idea, would be a black box, where you would put any number of random xmls, and get exactly what the accountant wanted with one button... so an impossible task.