UMLt

UMLt is an extension of the Unified Modeling Language (UML) that adds explicit temporal modeling capabilities to represent time-dependent behavior, versioning, and lifecycle evolution of software systems. Designed for environments where timing, sequencing, and history are essential, UMLt enables modelers to capture when events occur and how components change state over time.

Origin and status: UMLt emerged as a community-driven extension in the 2010s, building on UML's profile and extension mechanisms. It is not an official OMG standard, but has been explored in academic and industrial contexts to prototype time-aware modeling and to annotate UML diagrams with temporal semantics.

Core concepts: temporal states and transitions, time-stamped events, versioned components, and lifecycle timelines. Time annotations and temporal constraints can be attached to elements across diagram types. State machines can encode timing constraints; sequence and activity diagrams can include timestamps and duration information; class diagrams can carry version and aging metadata.

Notation and diagrams: UMLt uses stereotypes such as <<temporal>> and <<versioned>> to tag model elements, along with time attributes (time, duration) and constraints expressed in a lightweight timing language. It preserves familiar UML syntax, extending it with temporal semantics rather than replacing it.

Applications and tooling: modeling real-time systems, regulatory compliance, maintenance planning, and long-term asset evolution. Tool support is available in some UML tools via plugins or profiles, but coverage is inconsistent, and round-trip engineering can be challenging.

Limitations and reception: lack of formal standardization limits interoperability; educational overhead to learn temporal concepts; limited ecosystem of libraries and templates.

See also: Unified Modeling Language, UML profile, temporal databases, system lifecycle management.