IMS was the first yacht racing rule developed around the central idea of a Velocity prediction program (VPP).
The VPP was a complex computer program that integrated continuous hullform information in order to predict a given boat's speed potential in a given wind velocity.
Details on the VPP were openly available to the yachting community, in contrast to the earlier IOR system.
IMS is generally believed to have made significant leaps of progress forward from the IOR rule it displaced in terms of fairness and accuracy.
However, an improved, revised version of IMS was developed over the years 2006-2008, and known as the Offshore Racing Congress (ORC) rule.