Real-time systems are an important class of process control systems that need to respond to events under time constraints, or deadlines. Such systems may also be required to deliver service in spite of hardware or software faults in their components. This fault-tolerant characteristic is especially critical in systems whose failure can cause economic disaster and/or loss of lives. This paper reports recent research in the area of analytical modeling of the three major characteristics of real-time systems: timeliness, dependability, and external environmental dependencies. The paper starts with a brief introduction to analytical modeling frameworks such as Markov models and stochastic petri nets. This is followed by an examination of advances in modeling response-time distributions, reliability, distributed messaging services, and software fault-tolerance in real-time systems.

With the increased attention ATM is receiving to meet the needs of a wide variety of applications, tools are needed to help a network designer focus on the design at hand, rather than to spend time exhaustively learning the tools themselves. This is the concept behind IDEA. This paper introduces "modeling engines" chosen to be integrated into IDEA and presents a user interface for networking design. The first objective for IDEA is to demonstrate its usefulness for dependability modeling. Later objectives include incorporating performance and performability modeling.