Principles to Scaffold Mixed Textual and Iconic End-User Programming Languages

each action does, c) how conditions and actions are linked, and d) when and how rules are evaluated and executed (i.e., rule ordering). Program composition, the ability to assemble the language primitives in order to achieve the desired effects, presents even more challenges for the user. While children and other novice users can for the most part comprehend the if-then structure of rules, they have a difficult time mapping their own ideas into rules (11). Users have trouble determining what conditions and actions to use, as well as which conditions to combine with which actions. They also dislike writing many rules to accomplish seemingly simple tasks, especially if the rules are repetitive. Designing programming languages that are accessible to elementary school children is a complex task. Programming languages that contain visual elements provide a good starting point, because they are inherently appealing to many children. As novice users, however, children require additional support to use programming languages effectively. In this paper we describe five principles for designing end-user programming languages which address some of the obstacles we have observed when users attempt to create sophisticated programs. The principles are based on extensions we have made to Visual AgentTalk, the tactile programming component of the Agentsheets system. Although our research has centered on children, we believe that the discussion is widely applicable to the creation of languages for novice users of any age. Repenning and Ambach addressed some of these issues with their notion of tactile programming (23, 24). Based on our experience working with children, we have extended their model of tactile programming to further address these issues, and have formulated a number of guidelines for designing end-user languages that contain a mixture of pictures and text. We will situate the discussion of these guidelines in the context of two specific units from a life sciences curriculum.