Defines UML extensions for business modeling, by Rational.

Defines UML extensions for the Rational Objectory Process by Rational.

Defines the UML notation and provides examples, by Rational.

Defines the OCL, which is used to specify the well-formedness of the UML, by Rational.

Defines UML in terms of its abstract syntax presented in class diagrams, formal well-formedness rules expressed in OCL, and semantics expressed in text, by Rational.

An introduction to the UML that provides a road map to the other documents, by Rational.

UML 1.4 Diagrams as quick reference in PDF Format.

The PDF version of UML 1.3R9 which is currently under work to become the UML 1.4 standard. (Rational)

An online user's guide (UML 1.3) for Visual Paradigm for UML CASE Suite. (Visual Paradigm)

This series of documents defines the Unified Modeling Language (UML), a language for specifying, visualizing, and constructing the artifacts of software systems as well as for business modeling. The UML represents a collection of "best engineering practices" that have proven successful in the modeling of large and complex systems. (Rational)

A quick reference of the UML notation implemented in Rational Rose 4.0. (Rational)

Unified Modeling Language References including version 1.1 to 1.4 (by Visual Paradigm).

Aa complete reference which can be downloaded for off-line use, by Zvon.