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Unified Modeling Language (UML) was born from the fusion of the three methods required in the field of object modeling in the mid-1990s: OMT, Booch and OOSE. Major industrial players (IBM, Microsoft, Oracle, DEC, HP, Rational, Unisys, etc.) join the effort and propose UML 1.0 to the OMG (Object Management Group), which accepts it in November. 1997 in its version 1.1. The current version of UML in 2008 is UML 2.1.1 which is needed more than ever as a standardized modeling language for software modeling.

History of modelizations by objects

The methods used in the 1980s to organize imperative programming (notably Merise) were based on separate modeling of data and processing. As object-based programming becomes more important in the early 1990s, the need for a suitable method becomes obvious. More than fifty methods appeared between 1990 and 1995 (Booch, Relation-Class, Fusion, HOOD, OMT, OOA, OOD, OOM, OOSE, etc.), but none managed to win. In 1994, consensus was built around three methods:

• OMT by James Rumbaugh (General Electric) provides a graphic representation of the static, dynamic and functional aspects of a system;
• OOD by Grady Booch, defined for the Department of Defense, introduces the concept of package;
• OOSE by Ivar Jacobson (Ericsson) bases the analysis on the description of user needs (use case, or use cases).

Each method had its advantages and its supporters. The number of methods in competition had been reduced, but the risk of a break-up remained: the profession could be divided between these three methods, creating as many intellectual continents that would have difficulty communicating.

Eventful and almost miraculous, the three gurus who each ruled one of the three methods agreed to define a common method that federate their respective contributions (they are called since "the Amigos"). UML (Unified Modeling Language) was born from this convergence effort. The adjective unified is there to mark that UM unifies, and therefore replaces.

In fact, and as its name suggests, UML does not have the ambition to be exactly a method: it's a language.

Unification progressed in stages. In 1995, Booch and Rumbaugh (and a few others) agreed to build a unified method, Unified Method 0.8; in 1996, Jacobson joined them to produce UML 0.9 (note the replacement of the word method by the word language, more modest). The most important players in the world of software are associated with the effort (IBM, Microsoft, Oracle, DEC, HP, Rational, Unisys, etc.) and UML 1.0 is submitted to the OMG (5). In November 1997, the OMG adopted UML 1.1 as a modeling language for object information systems. The current version of UML in 2008 is UML 2.1.1 and the improvement work is continuing.

UML is therefore not only an interesting tool, but a standard that is required in object technology and to which all the major players in the field have joined, actors who have contributed to its development.

UML 2.0 thus contains thirteen types of diagrams representing as many separate views to represent particular concepts of the information system. They fall into two main groups:

Structural diagrams or static diagrams (UML Structure)

• class diagram
• Object diagram
• Component diagram
• Deployment diagram
• package diagram
• Composite Structure Diagram

Behavioral diagrams or dynamic diagrams (UML Behavior)

• use case diagram
• Activity diagram
• state machine diagram
• Interaction diagrams
• Sequence diagram
• communication diagram (Communication diagram)
• Interaction overview diagram
• Timing diagram

These diagrams, which are of different usefulness depending on the case, are not necessarily all produced during modeling. The most useful for project management are the diagrams of activities, use cases, classes, objects, sequences and transitions. The component, deployment and communication diagrams are especially useful for the project management to whom they make it possible to formalize the constraints of the realization and the technical solution.