Ivar Hjalmar Jacobson (born in Ystad, Sweden, on September 2, 1939) is a Swedish computer scientist. He got his Master of Electrical Engineering degree at Chalmers Institute of Technology in Gothenburg in 1962 and a Ph.D. at the Royal Institute of Technology in Stockholm in 1985 on a thesis on Language Constructs for Large Real Time Systems.
In 1967 he proposed the use of software components in the new generation of software controlled telephone switches Ericsson was developing. In doing this he invented sequence diagrams, and developed collaboration diagrams. He also used state transition diagrams to describe the message flows between components.
Jacobson saw a need for blueprints for software development. He 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 cases as a way to specify functional software requirements.
In April 1987 Jacobson quit Ericsson and started Objective Systems. A majority stake of the company was acquired by Ericsson in 1991, and the company was renamed Objectory AB. Jacobson developed the software process OOSE at Objectory circa 1992.
In October 1995 Ericsson divested Objectory to Rational Software and Jacobson started working with Grady Booch and James Rumbaugh (known collectively as the Three Amigos) to first create the UML, and later develop the Rational Unified Process. Rational was bought by IBM in 2003 and Jacobson decided to quit, but he stayed on until May 2004 as an executive technical consultant.
In mid 2003 Jacobson formed Ivar Jacobson International (IJI) which is an umbrella company for Ivar Jacobson Consulting (IJC) which operates across 4 continents with offices in the UK, US (West and East Coast), Europe, Scandinavia, China, Korea, Singapore and Australia.
In November 2005, Jacobson announced the Essential Unified Process or “EssUP” for short. EssUP is a new “Practice” centric software development process that stands on the shoulders of modern but established software development best practice. It is a fresh new start, integrating successful practices sourced from the three leading process camps: the unified process camp, the agile software development camp and the process improvement camp. Each one of them contributes different capabilities: structure, agility and process improvement.