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Rational Software
Industry Application development tools
Fate Acquired by IBM
Founded 1981 (1981)
Founder(s) Paul Levy and Mike Devlin
Defunct February 20, 2003 (2003-02-20)
Key people Mike Devlin (previous CEO)
Website www.ibm.com/software/rational/

Rational Machines was founded by Paul Levy and Mike Devlin in 1981 to provide tools to expand the use of modern software engineering practices, particularly explicit modular architecture and iterative development. Rational was sold for US$2.1 billion to IBM on February 20, 2003.

Rational Environment[edit]

First released in 1985, the Rational Environment was an integrated development environment for the Ada programming language, which provided good support for abstraction through strong typing. Its goal was to provide the productivity benefits associated with academic single-user programming environments to teams of developers developing mission-critical applications that could execute on a range of computing platforms.

The Rational Environment was organized around a persistent intermediate representation (DIANA), providing users with syntactic and semantic completion, incremental compilation, and integrated configuration management and version control. To overcome a conflict between strong typing and iterative development that produced recompilation times proportional to system size rather than size-of-change, the Rational Environment supported the definition of subsystems with explicit architectural imports and exports; this mechanism later proved useful in protecting application architectures from inadvertent degradation. The Environment's Command Window mechanism made it easy to directly invoke Ada functions and procedures, which encouraged developer-driven unit testing.

The Rational Environment ran on custom hardware, the Rational R1000, which implemented a high-level architecture optimized for execution of Ada programs in general and the Rational Environment in particular. The horizontally-microprogrammed R1000 provided two independent 64-bit data paths, permitting simultaneous computation and type checking. Memory was organized as a single-level store; a 64-bit virtual address presented to the memory system either immediately returned data, or triggered a page fault handled by the processor's microcode.

The company's name was later changed from "Rational Machines" to Rational Software Corporation (RATL) to avoid emphasizing this proprietary hardware when Rational merged with Verdix Corporation, a public company, on 30 March 1994. [1]

Rational provided code generators and the cross-debuggers for then-popular instruction set architectures such as the VAX, Motorola 68000, and x86; much of this was accomplished through a partnership with Tartan Labs, founded by Bill Wulf to commercialize his work on optimizing code generators semi-automatically produced from architecture descriptions (PQCC).


Rational's field Practices underlying the later Rational Unified Process (RUP) - iterative development, component-based architecture, modelling, continuous developer-driven testing, requirements management, and automated testing—are all traceable to this experience base.

Second-generation products[edit]

In 1990, Rational launched three parallel development efforts: re-implementation of the Rational Environment (for Ada) to run on Unix-based workstations from Sun and IBM, development of a comparable Rational Environment for C++ to run on Unix-based workstations from Sun and IBM, and development of a workstation-hosted modeling tool called Rose that supported a graphical notation developed by Grady Booch. Apex, the Rational Environment for Ada, was launched on Sun and IBM Unix platforms in 1993, and the Rational Environment for C++ followed on the same platforms a year later. A version of Apex that ran on Microsoft Windows NT was successfully developed and released by Rational's Bangalore team.

Rose 1.0 was introduced at OOPSLA in 1992, but performed poorly in multiple dimensions and was withdrawn from the market.

The development of Rose 2.0 combined a Windows-based Booch notation editor called Object System Designer (acquired from Wisconsin-based Palladio) with a new intermediate representation, and with new semantic analysis, code generation, and reverse engineering capabilities. The latter, which allowed prospective customers to analyze existing C++ code to produce "as-built" navigable class diagrams, helped overcome Rational's late re-entry into the market for object-oriented modeling tools. Rose 2.0 ran on Windows PCs and on several Unix-based workstations.

UML and RUP[edit]

In 1994, Rational merged with Verdix, a public company that produced a wide array of Ada compilers targeted to many architecture/OS combinations. The resulting entity was named "Rational Software", and promptly integrated the Rational Ada and C++ environments with the code generators and runtimes developed by Verdix.

In 1995, James Rumbaugh joined the company, and Rational acquired Ivar Jacobson's firm Objectory AB from Ericsson. With Grady Booch already aboard, this brought within one company three of the leading object-oriented software methodologists. These three experts attempted to unify their work. To eliminate the method fragmentation that they concluded was impeding commercial adoption of modeling tools, they developed Unified Modeling Language (UML), which provided a level playing field for all tool vendors. It was this collaboration effort that earned Rumbaugh, Jacobson and Booch the moniker "The Three Amigos" within the software engineering industry. At its 1.0 release, the Unified Modeling Language was contributed to the Object Management Group, which has managed its subsequent development.

Philippe Kruchten, a Rational techrep, was tasked with the assembly of an explicit process framework for modern software engineering. This effort combined the HTML-based process delivery mechanism employed by Objectory with Rational's 15-year experience base in working with customers developing significant software systems. The resulting "Rational Unified Process" (RUP) completed a strategic tripod:

  • a tailorable process that guided development
  • tools that automated the application of that process
  • services that accelerated adoption of both the process and the tools.


The momentum generated by Rose and the UML enabled Rational to establish a partnership with developers to the Windows platform; Rational's aim was to secure Microsoft's public support for visual modeling.

Rational peaked at $850M in revenues and 4000 employees. After the dot-com crash, its revenues declined to $650M, but it was dominant, profitable, and cash-rich (~$600M) when its founders chose to sell the company to IBM for $2.1B. The acquisition was announced on 6 December 2002 and was completed before the market opened 21 February 2003.[2]

See also[edit]


  1. ^ "Merger with Verdix". RATL. 2002-06-01. Retrieved via web.archive.org 2014-01-05. 
  2. ^ "IBM Completes Acquisition of Rational Software". IBM. 2003-02-21. Retrieved 2008-07-18. 

External links[edit]

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