Intentional processing as a key for rational behaviour through natural interaction

28 pages, 13 figures.-- Special Issue: "Symbiotic Performance between Humans and Intelligent Systems".This paper presents an interaction model pursuing flexible and coherent human–computer interaction. Starting from a cognitive architecture for Natural Interaction, an agent-based design is presented, focusing particularly on the role of the interaction agent. Regarding the intentional processing within this agent, the Threads Model is proposed. Finally, its implementation is described and evaluated to find out the integrity of the intentional approach.We thank the ISYS research group at the Technical University of Madrid and the LABDA research group at the Carlos III University of Madrid for their support during the design and development of the interaction agent, and everyone involved in the ADVICE (IST 1999-11305), VIP-ADVISOR (IST 2001-32440), and recent IntegraTV4All (FIT-350301-2004-2) projects for their hard work