1. A method for controlling behavior of model embodiment as a group of interactive objects in an object oriented computer programming system, wherein the method is executed by a computer, comprising the steps of: storing in memory means data describing the behavior of said model according to set of constraint on said behavior of said model, at least one of said constraints describing a temporal behavior of said model; determining actions to be performed by said interactive objects and times at which said actions are to be performed according to said set of constraints; generating events, each event comprising a representation of a message to be sent to said model for causing said model to perform one of said actions; each event further comprising a time stamp representing a time at which the message is to be sent; and generating a visible output in response to at least one of said actions performed by said interactive objects