User Modeling 2003 : 9th International Conference UM 2003 Johnstown PA USA June 22 26 2003 Proceedings This book constitutes the refereed proceedings of the 9th International Conference on User Modeling UM 2003 held in Johnstown PA USA in June 2003. The 20 revised full papers and 28 revised poster papers presented together with 12 abstracts were carefully reviewed and selected from 106 submissions. The papers are organized in topical sections on adaptive hypermedia adaptive Web natural language and dialogue plan recognition evaluation emerging issues of user modeling group modeling and cooperation applications student modeling learning environments natural language and paedagogy and mobile and ubiquitous computing