Guest editorial to the special issue on UML2003.

The article presents an overview of the research papers which were presented during the 2003 Unified Modelling Language conference. A systematic way of designing interactions by stepwise refinement was developed. One paper describes a snapshot sequence language which has been implemented to help designers to make better use of complex snapshots of a given model. One paper describes the author's experiences with a tool called Netsilon which has been developed to apply the model-driven engineering approach to web applications.