International Journal of User-System Interaction 14(2) 2021, 47-67 © MatrixRom A Profile and Design Space for Characterizing User Interface Adaptation Víctor López-Jaquero 1 , Vivian Genaro Motti 2 , Francisco Montero 1 , Pascual González López 1 , and Nicolas Burny 3 1 Laboratory of User Interaction and Software Engineering (LoUISE), Computer Science Dept., University of Castilla-La Mancha, Campus Universitario, 02071 Albacete, Spain 2 Department of Information Sciences and Technology (IST), Volgenau School of Engineering, George Mason University, Engineering Building, Rm. 5350, Fairfax Campus, USA 3 Louvain Research Institute in Management and Organizations (LouRIM), Université catholique de Louvain, Place des Doyens, 1 – B-1348 Louvain-la-Neuve, Belgium E-mail: VictorManuel.Lopez@uclm.es, fmontero@dsi.uclm.es, vmotti@gmu.edu, Pascual.Gonzalez@uclm.es, nicolas.burny@uclouvain.be Abstract. To better characterize the adaptation process of a user interface, we introduce an adaptation profile and a design space based on the seven adaptation stages defined in the GISATIE life-cycle: goals, initiative, specification, application, transition, interpretation, and evaluation. The adaptation profile expresses who is responsible for ensuring each adaptation cycle: one or several end users, one or several machine agents, one or many third parties, and any combination of the former. The adaptation design space expresses seven key dimensions along which adaptation can be decided and designed: autonomy level, granularity level, task resuming granularity, user interface deployment, technological space coverage, user feedback, and modality. Some examples are included to illustrate how to use this profile and design space for two systems ensuring user interface adaptation to some extent. Keywords: adaptation profile, design space, user interface adaptation DOI: 10.37789/ijusi.2021.14.2.1 1. Introduction Since its inception in the late eighties (Browne et al., 1986; Cockton, 1988; Totterdell and Rautenbach, 1990), user interface (UI) adaptation (Jameson, 2003) has often be justified by the desire to see the UI adapted to the end user and not the end user forced to become adapted to the UI. While this goal