UML Diagrams

UML stands for Unified Modeling Language.
UML is used to model an application structures, behavior and even business processes.
It is a visual modeling language used for analysis, design, implementation of software based systems, modeling business and similar processes.
It is a standard modeling language, not a software development process.
It is a standard notation for the modeling of real world objects as a first step in developing an object-oriented methodology.

History of UML

Unified Modeling Language (UML) was developed by Grady Booch, Ivar Jacobson, James Rumbaugh at Rational Software in 1994-95.
It was motivated by the desire to standardize the disparate systems and approaches to software design.
It is created by the Object Management Group (OMG) in 1997.
It was also published by the ISO (International Organization for Standardization) in 2005.
It is a standard language for specifying, visualizing, constructing and documenting the artifacts of the software systems.

UML provides a standard for software development.
It reduces the development time and cost to develop diagrams of UML using supporting tools.
It has a large visual element to construct.
Communication with programmers and outside contractors will be more efficient.
The past faced issues by the developers no longer exists.

UML is large and complex.
UML is difficult to synchronize the code with models.
It is difficult to keep multiple models or diagrams consistent with each other.
UML is limited to what the vendor provides out of the box, usually some form of a code generator.
It does not define a standard file format, which means each UML tool vendor stores the representation of its UML model in proprietary format.

UML is an international standard.
UML becomes the most successful modeling language in the history of computer technology.
UML is widely known, used and supported in tools.

UML provides guidance as to the order of a team's activities.
UML directs the tasks of individual developers and the team as a whole.
It offers criteria for monitoring and measuring a project's products and activities.
It is process independent.
It provides a mechanism for adjusting the language and better options for the modeling of behavior.
It is suitable for use case driven, iterative and incremental development processes.
It provides better options for the modeling of behavior.
It adds the definition of formal and completely defined semantics.

Following are the main highlights in UML which describe the purpose of a UML and why is it widely used & supported in various tools:

More precise definitions of concepts and their relationships.
Modularized structure.
Improved language organization and support for modeling large-scale software systems.
Simplified compliance model for easier interworking and improved support for defining domain-specific languages (DSLs).
Increased level of precision to better support MDD.
Modeling of distributed concurrent process flows, complex software structure and end-to-end behavior.