What is UML?

UML provides a means to visualize a system's architectural blueprints in a diagram, including elements such as:

• any activities
• individual components of the system and how they can interact with other software components
• how the system will run
• how entities interact with other components and interfaces
• external user interface

UML proved so successful that eventually, it ended up being used in other areas such as business modeling, or modeling non-software systems. A UML diagram is a partial graphical representation of a model of a system (either under design or already in use). It contains graphical elements, such as nodes connected with edges, but may contain additional documentation written as text.

The language defines two categories of diagrams, although there is no formal interdiction against combining different types of diagrams.

Structure diagrams show the static structure of the system and its parts and how those parts relate to each other on different abstraction and implementation levels. The elements in a structure diagram represent the meaningful concepts of a system and may include abstract, real world, and implementation concepts. Behavior diagrams, on the other hand, show the dynamic behavior of the objects in a system, which can be described as a series of changes to the system over time.