Prerequisite Checkpoint: Long-Running Work Needs Goal Semantics

An action is useful when work has a lifecycle: goal acceptance, progress feedback, completion, and possibly cancellation.

For one robot-side behavior, identify:

goal:
feedback:
result:
cancel condition:

Then ask whether a service would lose important semantics. If the operation may take time and the caller needs progress or cancellation, a one-shot request/response can be the wrong model.

Bridge comparison

A Java loop or command sequence that reports progress locally is not automatically a ROS action. The middleware-visible action relationship needs its own runtime evidence.

Write one safe claim about local Java behavior and one separate claim about ROS action behavior. Then state what integration evidence would be required to connect them.

If action concepts are new, return to ros2-for-students. This bridge assumes the primitive and focuses on architecture choice.