R. Straeten, T. Mens, J. Simmonds, and V. Jonckers. UML 2003 – The Unified Modeling Language, volume 2863 of Lecture Notes in Computer Science, page 326--340. Springer, (2003)
D. Frankel, P. Hayes, E. Kendall, and D. McGuinness. 1st International Workshop on the Model-Driven Semantic Web (MDSW2004), Monterey, California, USA, (September 2004)