Book excerpt: This book constitutes the refereed proceedings of the 7th International Conference on the Unified Modeling Language, UML 2004, held in Lisbon, Portugal, in October 2004. The 30 revised full papers presented together with summaries on the workshops and tutorials were carefully reviewed and selected from 135 technical paper submissions. The papers are organized in topical sections on metamodeling, aspects, profiles and extensions, OCL, model transformation, verification and model consistency, security, and methodology.