What is UML? The Unified Modelling Language Explained

In 1997 the OMG (Object Management Group) developed the Unified Modelling Language (UML) as a common architectural framework for modelling object oriented systems and applications. UML is derived primarily from the strengths of three notations; Bouch OOD (Object Oriented Design), Rumbaugh OMT (Object Modelling Technique) and Jacobson OOSE (Object Oriented Software Engineering).

The OMG described the Unified Modelling Language as a language representing unified best engineering practices for specifying, visualising, constructing and documenting the elements of business modelling, software and even non-software systems.

• Specification: UML can be used for specifying “what” is required of a system and “how” a system may be implemented. It captures the all-important requirements, analysis, design and implementation decisions that need to be established during a system development lifecycle.
• Visualisation: The graphical nature of UML allows the visualisation of systems before they are implemented. Using shapes representing well defined semantics to communicate to a wider audience more succinctly than a descriptive narrative and more comprehensively than what often can be represented by a programming language.
• Construction: UML can be used to guide and craft the implementation of a complicated system. Furthermore, with the aid of various case tools on the market, it is possible to generate object orientated source code from UML models and also possible to reverse engineer source code into UML Models.
• Documenting: UML offers a means of capturing knowledge and documenting deliverables such as requirements documents, functional specifications and test plans. These are all critical in controlling, measuring and communicating a system throughout its lifecycle.

These four modelling applications of UML should not be confused with a process. There are many processes available which use UML. Furthermore there are many tools available on the market that aid the construction of a UML model and in some cases, also facilitate adherence to a particular process.

The Unified Modelling Language is not:

• A Process: It is a modelling toolkit with its own notation and syntax. A process goes further by describing the steps that should be followed when developing software including which diagrams are produced and in which order, who does what and so on. The premise behind UML is that it is process independent but enables and supports further processes.
• A Visual Programming Language: It is a visual modelling language from which programs can be derived. The notation behind UML modelling is comprised of a set of specialised shapes used for the construction of different kinds of software diagrams, while the UML syntax specifies how these shapes can be defined.

As such further to learning the UML Basics it is recommended that:

• A process or methodology is adopted
• A UML development tool is utilised

Dunstan Thomas recommends the use of Sparx Systems Enterprise Architect as your UML development tool.