An object oriented (OO), discrete event simulation engine for on-line simulation applications has been conceptualized, designed, developed and tested. This paper describes the concepts, the advantages of OO simulation and results achieved in a near-real-time application. Flexibility to customize, real time status initiation, and capability for modeling complex resource and process relationships are some of the salient features. The objective of the work is to demonstrate the use of the developed OO simulation engine in the semiconductor backend manufacturing operation for dynamic scheduling applications, and optimization of equipment utilization, cycle time and delivery performance. Capability for “what if” analysis and auto generation of simulation model at a desired frequency, are examples of other features considered in the development.