Can u be more specific? As u can see, there are no imports for processMulipart() and singlePart() methods. In order to call one drl function in another u need to access it through static call from a "class" that has very same name. I've got that tip on #drools irc.
I'm using drools 3.0.6, and pretty much a newbie in drools, perhaps you have a better solution?