UML came about when James Rumbaugh joined Grady Booch at Rational Software. They both had object oriented syntaxes and needed to combine them. Semantically they were very similar, it was mainly the symbols that needed to be unified. The result was UML 1.0

Then Ivar Jaconson joined them. He brought with him the syntax for use cases which was added in UML 1.1. The Object Management Group adopted the UML1.1 specification in November 1997 making it an independent industry standard. Some small changes were made in in versions 1.3 and 1.4. Version 2.0 is currently being researched.