Patternprogrammer: yet another rule-based programming environment for children

Graphical rewrite rules are often used in programming environments for children. These rules consist of two parts: a left-hand side, which is visually matched in the environment, and a right hand side, which replaces the matched area. Programs using graphical rewrite rules typically describe behaviour 2D visual simulations where the program describes how visual agents move around a 2D space and interact with other agents. These types of programming environments are very simple yet very powerful. Despite the simplicity of graphical rewrite rules, evaluations of these programming environments have found the environments suffer two flaws. The first flaw is that children have difficulties understanding the implications of the rule scheduler. The second flaw is that children create one or two large rules to describe complex behaviour rather than creating many small rules. This paper presents another rule-based programming environment for children. The environment is designed to avoid these problems at the cost of an intuitive rule matching algorithm. Informal usability tests found that people initially make some mistakes comprehending how PatternProgrammer applies their rules, but quickly adjust their cognitive model to one that accurately reflects PatternProgrammer’s scheduling and matching behaviour.