The MITRE Corporation has its roots in distributed computing and has been a principal player in this field from its very beginning. In the 1950s, MIT, IBM, AT&T, Burroughs, and others designed the Semi-Automatic Ground Environment (SAGE) air defense system to protect the United States from long-range bombers and missiles. SAGE was actually a distributed computing system, with pairs of main and fail-over computers in multiple control centers across the country. MITRE was founded in 1958 to conduct all research, development, and systems engineering for the SAGE project, and MITRE’s early years were totally dedicated to SAGE. During the 1960s, MITRE applied the same distributed computing techniques to its first contract with the Federal Aviation Administration: the SAGE Air Traffic Integration (SATIN) project. In the same time period, the Air Force directed MITRE to design the now-famous North American Aerospace Defense Command (NORAD) Combat Operations Center for Cheyenne Mountain along the same lines as SAGE.

Distributed computing became available to a more general development community in the 1970s, with the UNIX operating system providing a way to execute a software routine on another computer using remote procedure calls (RPCs). RPCs were a simple concept in an operating system, but their use in real applications was complex because they forced programmers to concern themselves with registering process numbers, host names, input and output data compatibility, process management, error handling, and time synchronization. Over time, a family of support library routines developed and was included in UNIX. They were eventually standardized in the 1980s by the Open Software Foundation as the Distributed Computing Environment (DCE). Several vendors built DCE products and ported them to various operating systems in addition to UNIX. DCE represented a huge step forward. It was vastly easier to use than the basic operating system calls, and the vendors provided documentation and support beyond the UNIX operating system online documentation. DCE also included rudimentary services for naming (a Yellow Pages-like lookup service), time, and security, all essential to any distributed computing application.

The Common Object Request Broker Architecture (CORBA) standard was written in the early 1990s. In the same time frame, other vendors developed Message-Oriented Middleware (MOM), which placed inter-machine messages in a queue so that if a machine were busy or off line, its messages would be saved until it was back in service. More recently, Sun Microsystems introduced its Java language Remote Method Invocation and Jini, a method of building systems in which code is downloaded to the user’s machine only when it is needed. CORBA has recently been extended to real-time environments. Most implementations of these technologies use the RPC mechanism.

Today, the technical literature abounds in articles about Web Services, a loosely coupled architecture in which most functionality resides in services accessible on the network rather than installed on the user’s computer. Sun’s Java 2 Enterprise Edition standard for application servers is available today, and Microsoft .NET tools were officially released in 2002. There is also much current interest in eXtensible Markup Language (XML), used for data interoperability, which supports distributed computing through its XML-RPC function. The Simple Object Access Protocol (SOAP), originally part of the .NET concept, uses XML for messaging.

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