1. A method for business performance monitoring employing aggregation agents, comprising the steps of: receiving messages selected from the group consisting of time events and metric instances; maintaining metric instances in metric repositories, each of said metric instances containing a value, a time, and a correlation field, wherein said correlation field includes user-defined correlation variables which allow for correlations between metric instances; creating higher-level metrics which are Key Performance Indicators from lower-level metrics based on said time events and said metric instances; wherein the creating higher-level metrics which are Key Performance Indicators is performed in real time by the aggregation agents: sending said higher-level metrics which are Key Performance Indicators to said metric repositories; learning at least one relationship between metrics stored in said metric repositories; performing what-if analysis wherein said what-if analysis comprises the steps of: receiving hypothetical metric instances; applying a model of metric relationships; and generating estimated metric instances; outputting at least one model or tool in which Key Performance Indicators reflect every day operational measures in a timely fashion; receiving, by a computer-based knowledge agent, hypothetical business scenarios, followed by responding, by the knowledge agent, to the received hypothetical business scenarios with estimated outcomes.