According to the OMG specification, "The Unified Modeling Language (UML) is a graphical language for visualizing, specifying, constructing, and documenting the artifacts of a software-intensive system. UML offers a standard way to write a system's blueprints, including conceptual things, such as business processes and system functions as well as concrete things such as programming language statements, database schemas, and reusable software components."

Note that the UML is purely process independent, i.e., it is not tied up with a SLDC process. The basic purpose behind UML modeling is visualizing, constructing, specifying and documenting a system. It should be noted that UML is a standard; it is not a methodology, process or a procedure. Rather, we use UML as a standard that uses some predefined standard notations with a view to modeling and defining a software system, to document it and define the artifacts involved.