Rational Software

Rational Software was an independent software development company until 2003, when it was bought by IBM. Most of its products involved modelling and aiding in software development and maintenance.



Rational Software was founded by Paul Levy and Mike Devlin in 1980/1981 as a developer of software development tools. The product line included the R1000 computer, an Ada-only development computer with a integrated IDE. The company later ported the R1000 software to UNIX and sold the result as "Rational Apex".

In October 1994 James Rumbaugh joined the company and in the fall of 1995 Rational merged with Ivar Jacobson's firm Objectory AB. This created a company which had the three leading software metholodgy inventors, the "three amigos" (also called "the gang of three"): Grady Booch, James Rumbaugh and Ivar Jacobson in the same house. They started by creating Unified Modeling Language (UML); after that they merged their software development methodologies into Rational Unified Process (RUP).


Rational went into business difficulties and IBM acquired it in February 2003, incorporating it into the IBM Software Group Division where it became the fifth brand, alongside Websphere, Tivoli, DB2, and Lotus.

Rational products


Rose, a software modeling program, arose from a few engineers formerly at GE in Waukesha, Wisconsin. After Rational acquired the product, it moved much of the development to California.

Rational developed and maintained Rose, afterwards called Rational Rose, as a flagship product.

Rose originated to support Ada programming. It currently supports C++ and Java. Unlike many programming artifacts, which developers retain and maintain, Rose Models merely form a stage in the development of a program; hence designers and programmers can discard them after a few uses, because they can re-generate them from the developed program, using round-trip engineering.


Rose RealTime originated to support the development of complex reactive systems, typically ones written in C, C++ and Java. It combines the Real-Time Object Oriented Modeling (ROOM) method developed by Bran Selic at ObjecTime Corp, and the UML capabilities from Rational Rose. Rose RealTime supports a model-driven development approach that uses forward engineering to generate, directly from a UML model, up to 90% of the real-time application code found in telecommunications switches and industrial controllers. By annotating the UML model with action code, the model can produce 100% of the application code.

ObjecTime developed the original product in Kanata, Canada prior to its acquisition by Rational Software on December 14 1999.

Various products

Rational also acquired memory debugger Purify, software configuration management (SCM) tool ClearCase and software testing tool ClearQuest. Other Rational products included the automated documentation tool: SoDA - Software Documentation Automation.

After Microsoft developed Visual Test, Rational purchased the product rights.

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