As with many hot topics in information technology, a consensus has been formed about something being "a really good thing"-- an "architecture" in this case—even though no two people seem to define the term the same way. In fact, the Software Engineering Institute's Web site has an entire section devoted to various definitions of software architecture. If you aren't satisfied with any of the listed definitions, you can add your own via their Web site!

One of the definitions quoted most often was coined by David Garlan and Dewayne Perry at Carnegie Mellon University in 1995. It simply states that a software architecture is "the structure of the components of a program/system, their interrelationships, and principles and guidelines governing their design and evolution over time." The last phrase is important; it adds the concept of rules to what is typically seen as a static representation of a system. The work MITRE is doing now in support of our sponsors is intended to guide the development and evolution of Command and Control (C2), Intelligence, and Combat Support systems well into the next century. Those rules, which govern how the architecture is applied and then extended, are at least as important as the components and interfaces themselves.

The importance of establishing a sound architectural foundation for a system or system-of-systems has been acknowledged by the Defense Department, which has gone to great lengths to define what it considers to be the three primary architectural views—technical, system, and operational—and their relationships.

This issue of The Edge is devoted to a cross-section of the architecture-related efforts MITRE is working on in support of its sponsor community. The articles on the Defense Modeling and Simulation Office's "High Level Architecture" and The National Imagery and Mapping Agency's "NITRO" architecture are case studies of projects that define and implement domain-specific software architectures. The article, "Software Architecture in Reverse," discusses an approach for recovering a software architecture from an existing software system. The article, "New Architecture Directions," describes the Defense Department's new model for developing and describing architectures. There is also a summary and web address for the article "The Advanced Information Technology Services (AITS) Architecture," which describes MITRE's work in helping to define the next generation computing environment for C2 and Combat Support within the Defense Department. It represents architectural work being done at the "system-of-systems" level.

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For more information, please contact guest editor Rick Rudman using the employee directory.

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