Abstract—User interaction components of Augmented Reality (AR) systems have to be tested with users in order to find and fix usability problems as early as possible. In this paper we will report on a user-centered design approach for AR systems following the experience acquired during the design and evaluation of a software prototype for an AR-based educational platform. In this respect we will focus on the re-design of the user task based on the results from a formative usability evaluation. The basic idea of our approach is to describe task scenarios in a tabular format, to develop a task model in a task modeling environment and then to simulate the execution. Keywords—AR-based educational systems, task-based design, usability evaluation. I. INTRODUCTION NDERSTANDING the user tasks, how and why task modeling plays an important role in the design process is a pre-requisite to design a usable interactive system. Unfortunately, there are few techniques that support the design for usability of Augmented and Mixed Reality [7]. Task elicitation is more difficult for AR based systems than for traditional systems since real and virtual objects (computer generated) are integrated into a real environment. According to Azuma [2], AR systems are featuring an integration of real and virtual (computer generated images) into real environments, real time 3D interaction and targeting all senses (visual, auditory and haptic). Augmented Reality is a variation of Virtual Reality (VE) that supplements reality, rather than completely replacing it. AR technologies are expensive and require a lot of research and design effort to develop visualization and rendering software. On another hand, the mix of real and virtual requires appropriate interaction techniques. As pointed out by Hix et Manuscript received August 31, 2007. This work was supported in part by the FP6-027039 research project (ARiSE) and the FP6-507609 european research project (SIMILAR). Costin Pribeanu is with the National Institute for Research and Development in Informatics – ICI Bucureşti, Bd. Mareşal Averescu No. 8-10, 011455 Bucharest, Romania (phone: +40-(0)21 3160736; +40-(0)21 3161030; e-mail: pribeanu@ici.ro). Rytis Vilkonis is with the Natural Science Education Research Centre, Siauliai University, P.Visinskio Street 25-119, Siauliai , Lithuania (phone: + 370 41 595736; fax: + 370 41 595710; e-mail: vilkonis@yahoo.com). Dragoş Daniel Iordache is with the National Institute for Research and Development in Informatics – ICI Bucureşti, Bd. Mareşal Averescu No. 8-10, 011455 Bucharest, Romania (phone: +40-(0)21 3160736; +40-(0)21 3161030; e-mail: iordache@ici.ro). al. [4], the user interaction components of this kind of applications are often poorly designed and rarely tested with users. They proposed a design and evaluation framework having as central components user task analysis and formative evaluation. Formative usability testing is performed in an iterative development cycle and aims at finding and fixing usability problems as early as possible by testing the software with a relatively small number of users. It is especially effective to support the development of novel systems as they are targeted at a specific part of the user interface design. This paper aims at presenting a task-based approach undertaken in the framework of the ARiSE project. ARiSE (Augmented Reality in School Environments) is a research project that aims at creating an augmented reality technology for schools by adapting a virtual showcase used in museums. ARiSE will develop interaction scenarios for learning and associated software prototypes in order to assess the pedagogical effectiveness of the AR technology [1]. The 1 st prototype has been tested with users during a summer school organized in Hamrun, Malta. The objectives of the test were to assess the pedagogical effectiveness and usability of the prototype. Several evaluation techniques have been used: observation, usability questionnaire and focus group. In this paper we will elaborate on a user-centered design approach for AR systems based on the experience acquired during the design and evaluation of the 1 st prototype. In this respect, we took into account the positive and negative aspects mentioned by students and teachers and decided to re-design the task model and to enrich the interaction scenario. The rest of this paper is organized as follows. The evaluation context (platform, participants and tasks) and usability problems identified are briefly described in the next section. The design approach is presented in section 3. The paper ends with conclusion in section 4. II. RESULTS FROM A FORMATIVE EVALUATION A. The Evaluation Context The AR platform consists of 4 independent modules organized around a table on which real objects are placed. The platform has been registered by Fraunhofer IAIS under the trade mark Spinnstube ® . [3] In Fig. 1, the photo of a module is presented. A Task-Based Design Approach for Augmented Reality Systems Costin Pribeanu, Rytis Vilkonis, and Dragoş Daniel Iordache U International Journal of Social Sciences 2;4 © www.waset.org Fall 2007 209