Artifacts for Real-Time Systems

Real-time systems are those with particular requirements for timeliness or responsiveness, often with the constraint of hard deadlines. Such systems are often found in safety-critical applications. The Rational Unified Process describes the following additional artifacts intended specifically to meet the demands of developing such systems:

• Capsule : A capsule is a specific design pattern, which represents an encapsulated thread of control in the system. Capsules have ports, through which they communicate with other capsules.

• Protocol: A protocol specifies the way a set of ports communicate, the messages exchanged, and how they are ordered.

• Event: An event is the specification of an occurrence in space and time, or, less formally , an occurrence of something to which the system must respond.

• Signal: A signal is an asynchronous event that may cause a state transition in the state machine of an object.

These additional artifacts are stereotypes of class and are part of the design model. They support the particular approach for real-time system development defined in the Rational Unified Process, which is based on ideas presented in the textbook Real-Time Object-Oriented Modeling . ^[1]

^[1] Bran Selic, Garth Gullekson, and Paul T. Ward, Real-Time Object-Oriented Modeling . New York: John Wiley & Sons, 1994.