M.A.BRAMER University ofPortsmouth, UK This volume comprises the refereed technical papers presented at AI-2006, the Twenty-sixth SGAI International Conference on Innovative Techniques and Applications of Artificial Intelligence, held in Cambridge in December 2006. The conference was organised by SGAI, the British Computer Society Specialist Group on Artificial Intelligence. The papers in this volume present new and innovative developments in the field, divided into sections on AI Techniques, Knowledge Discovery in Data, Argumentation, Dialogue Games and Optimisation, Knowledge Representation and Management, Semantic Web, and Model Based Systems and Simulation. For the first time the volume also includes the text of short papers presented as posters at the conference. This year's prize for the best refereed technical paper was won by a paper entitled Combining Task Execution with Background Knowledge for the Verification of Medical Guidelines' written by a team comprising Arjen Hommersom, Perry Groot and Peter Lucas (University of Nijmegen, The Netherlands) and Michael Balser and Jonathan Schmitt (University ofAugsburg, Germany). SGAI gratefully acknowledges the long-term sponsorship of Hewlett-Packard Laboratories (Bristol) for this prize, which goes back to the 1980s. This is the twenty-third volume in the Research and Development series. The Application Stream papers are published as a companion volume under the title Applications and Innovations in Intelligent Systems XIV. On behalfofthe conference organising committee I should like to thank all those who contributed to the organisation of this year's technical programme, in particular the programme committee members, the executive programme committee and our administrator Mark Firman.