Design and Evaluation of an Event Architecture for Paper UIs: Developers Create by Copying and Combining

Abstract

This paper explores architectural support for interface ensembles comprising pens, paper, and PCs. We show how the event-based approach common to GUIs can apply to augmented paper, and describe additions to address paper's distinguishing characteristics. Most notably, we introduce techniques for integrating interactive and batched input handling, coordinating interactions across devices, and rapidly debugging applications that integrate paper and computation. To understand the developer experience of this architecture, we deployed the toolkit to 17 teams at another university for six weeks. Static analysis of the participants' code provided insight into the appropriateness of events for paper (e.g., programmers relied on debugging output to track event flow). We also distilled usage patterns, revealing that programmers composed simple gesture handlers from ink measurements. This desire for informal interactions inspired us to include abstractions for recognition. This study has implications beyond paper ' designers of graphical tools can provide visualizations for event flow, and examine API usage to inform toolkit revisions.