A common occurrence in the perception industry is that the words sensor and device are often ambiguous and used interchangeably. This can often lead to confusion, which is the last thing one wants in a complicated perception system. To that end, we don't use these terms at all! "Plex" is sufficient.
Here's a quick example: While an Intel® RealSense™ D435i could be referred to as a single "device" or "sensor", it's really a combination of several constituent components:
- Two infrared cameras
- A color camera
- An accelerometer and gyroscope (6-DoF IMU)
- A "depth" stream, synthesized from observations of the two infrared cameras
Each of these components are represented independently in the Plex, and any of these components can be a designated root component for the others.
We can even add an entire new RealSense™ module to the Plex with very little effort. Just create the components and constraints for the new RealSense™, and then connect the root components through a spatial and/or temporal constraint.
This formulation helps prevent ambiguity in our system. For example, in the old paradigm, one might ask for "the extrinsics between two Intel® RealSense™". This is not a useful question, since there are many ways to define that. If instead we now ask for the "extrinsics between color camera with UUID X and color camera with UUID Y", which is specific and unambiguous.