UML

Unified Modeling Language (UML) is a standardized general-purpose modeling language used in software engineering. It provides a standard way to visualize, specify, construct, and document the artifacts of a software system. UML is not a programming language; it defines notation and semantics for models that can be analyzed and evolved independently of any particular implementation.

UML originated from the consolidation of several object-oriented design methods, notably Booch, OOSE, and OOAD. The Object Management Group (OMG) released UML 1.0 in 1997 and has maintained it through UML 2.x, with major updates to improve semantics, execution, and interoperability. It is widely supported as an industry standard and has influenced subsequent modeling approaches, including SysML for systems engineering.

UML comprises a family of diagrams used to describe static structure and dynamic behavior. Structural diagrams include class, object, component, deployment, and package diagrams. Behavioral diagrams include use case, sequence, activity, state machine, communication, and interaction overview diagrams. UML 2.x introduced richer execution semantics and improved integration among diagram types, supporting more precise behavioral modeling and timing information.

The language emphasizes language independence, allowing models to be mapped to various implementation languages. It supports extension through profiles, stereotypes, and tagged values to tailor modeling for specific domains. Modeling tools can generate code and documentation from models, and support round-tripping updates between models and source code, enabling model-driven development.

UML is used to model software and systems to aid communication, analysis, and design. It is most effective for stable design decisions but can be heavy for small, rapid projects. Critics cite complexity and a steep learning curve, and some teams prefer alternatives such as SysML for systems engineering or BPMN for business process modeling.