Other System Definitions
• UML 1.3: A system is a collection of connected units that are organized to accomplish a specific purpose. A system can be described by one or more models, possibly from different viewpoints.
• IEEE Std. 610.12-1990: A system is a collection of components organized to accomplish a specific function or set of functions.
• Rechtin adds the following to his definition: “The whole is greater than the sum of the parts, that is, the system has properties beyond those parts.” p28 (1991). We prefer Rechtin’s definition and emphasize that not only does the system perform a unique function, but it has unique characteristics or qualities that are inherent in the system and not just the parts (you couldn’t put the turbocharged engine of a Dodge Stealth in an Escort and get the performance of the Stealth, for example).
Note on System Thinking
Thinking about systems, or from a systems perspective, has its roots in work by Buckminster Fuller and Russell Ackoff, among others. More recently, it has been recognized as a field in of itself, called “systems thinking”, and has intellectual leaders such as Peter Checkland and Peter Senge (author of “The Fifth Discipline”). Eberhardt Rechtin’s “Systems Architecting: Creating and building complex systems” (1991) remains one of the most important works in this domain, and has been highly influential in our approach to architecture.