1. (original) a computer method of modeling a business activity, comprising the steps of: (a) defining one or more business classes including storing in a digital electronic format said one or more business classes as well as the relationships existing between said one or more business classes; (b) representing a subject business activity as an interaction between one or more business classes; and (c) tying business rules or methods to individual instances of the business classes such that two instances of a same class can respond differently to a given business activity.