Codein—A New Notation for GOMS to Handle Evaluations of Reality-Based Interaction Style Interfaces

We propose a new diagrammatic notation system for Goals, Operators, Methods, Selection rules (GOMS), called Codein, with extensions to support the evaluation of Reality Based Interaction Styles. The proposed notation gives added power to GOMS to model and evaluate the task completion time of parallel actions during the performance of a task, something that was previously only possible using CPM-GOMS, which is far more complicated to use. Codein's evaluative power is verified through an experiment. The first condition of the experiment compares the completion time predicted by a GOMSL model, a Codein model, and the actual completion time of participants in a direct manipulation task. The second compares the completion time of participants in a Tangible User Interface task with predictions by a GOMSL model and a Codein model. Predicted task times by Codein in both conditions come close to the actual experimental results.