In the mid 1990's three of the big names is OOA&D - Grady Booch, Jim Rumbaugh and Ivar Jacobsen - came together at Rational® Corporation to combine their software development methods into a single way of working, that they hoped would become an industry standard for software development. As a crucial first step to this goal they realised they needed to unify the notations they used to express the analysis and design documents (often called artefacts) related to those methods.  This effort resulted in the submission to the industry body, the Object Management Group (OMG), of the Unified Modeling Language specification. After some additional contributions and much discussion, this was adopted by the OMG in 1997 and has rapidly established itself since as the de facto standard for documenting OOA&D efforts by software developers the world over. On its adoption by the OMG, Rational® handed over the specification of, and control over, the notation to the OMG who now formally administer amendments and upgrades to the language. A full UML specification is available from the OMG website in PDF format. It runs to over a 1000 pages currently - so it is definitely not for the fainthearted.  In addition, there are many excellent books giving either overviews of the language or in depth coverage of some aspect of it.  (See our links  section for some suggestions).
 

continued...