  End-user programming (EUP) tools must balance user control with the robot's
ability to plan and act autonomously. Many existing task-oriented EUP tools
enforce a specific level of control, e.g., by requiring that users hand-craft
detailed sequences of actions, rather than offering users the flexibility to
choose the level of task detail they wish to express. We thereby created a
novel EUP system, Polaris, that in contrast to most existing EUP tools, uses
goal predicates as the fundamental building block of programs. Users can
thereby express high-level robot objectives or lower-level checkpoints at their
choosing, while an off-the-shelf task planner fills in any remaining program
detail. To ensure that goal-specified programs adhere to user expectations of
robot behavior, Polaris is equipped with a Plan Visualizer that exposes the
planner's output to the user before runtime. In what follows, we describe our
design of Polaris and its evaluation with 32 human participants. Our results
support the Plan Visualizer's ability to help users craft higher-quality
programs. Furthermore, there are strong associations between user perception of
the robot and Plan Visualizer usage, and evidence that robot familiarity has a
key role in shaping user experience.
