Ivar Hjalmar Jacobson is a Swedish computer scientist, born in Ystad, Sweden, on September 2, 1939.
He received a Masters in Electrical Engineering from Chalmers Institute of Technology in Göteborg in 1962, and a Ph.D. from the Royal Institute of Technology in Stockholm in 1985 for a thesis on Language Constructs for Large Real Time Systems.
In 1967, he proposed the use of software components in the development of the new generation of software controlled telephone switches Ericsson was developing at the time. In doing this, he invented sequence diagrams and also developed collaboration diagrams. In addition, he applied state transition diagrams to describe the message flow between the components.
He thought that there needed to be blueprints for software development, and was one of the original developers of SDL (Specification and Description Language). In 1967, SDL became a standard in the telecoms industry.
At Ericsson he also invented use case as a way to write down software requirements.
In April 1987 he left Ericsson and started Objectory AB, where he developed the software process OOSE in the early nineties.
In October 1995 he merged Objectory with Rational Software and started working with Grady Booch and James Rumbaugh to develop first UML and later Rational Unified Process. Rational was bought by IBM in 2003 and Ivar decided to quit, but he stayed on until May 2004 as an executive technical consultant.
In November 2005, Jacobson announced he was working with Microsoft to produce an Essential Unified Process for Visual Studio Team System, that he describes as a "super light and agile" RUP.