Telemetry streams FAQ

What are streams?

A telemetry stream is a named sequence of datapoints. See How telemetry streams work.

What are tags and how do they relate to streams?

The telemetry stream name is the primary dimension used in the Formant UI for grouping visualization. Tags are used as metadata to describe additional dimension within a stream. Tags also allow datapoints to be found or grouped by filtering or searching.

What should be modeled as a stream name as opposed to a tag?

There are no hard and fast rules, but the following may offer some guidance.

Stream Name

  • The stream name is treated as the primary dimension by the Formant UI for grouping in visualizations, filtering, aggregation, etc.
  • The stream name is usually a description of a sensor measurement, like battery.level, or a concept, like odometry.pose.
  • The stream name often represents a relatively stable concept in your application.
  • If you are a ROS user, stream name often maps well onto the concept of a ROS topic name.


  • Tags are treated as additional dimensions
  • Tags often represent a concept that can grow to take on additional possible values over the lifetime of your application, such as a software_version, a customer_id, or a robot_id
  • Tags often encode additional metadata about the source of the measurement, as opposed to a description of the measurement