 This revised version of the method without the tool is commonly known as SDM2.SDM2 was a revised version of SDM that attempted to solve a basic problem that occurred often in SDM projects; the delivered system failed to meet the customer requirements.Though any number of specific reasons for this could arise, the basic waterfall method used in SDM was a recipe for this problem due to the relatively large amount of time spent by development teams between the Definition Study and the Implementation phases.