Observability

A new term to me, but apparently in use to understand how a system operates to work with it or debug systems.   The description makes logical sense, the details are more complex.

Software Engineering: Observability

Observability — A 3-Year Retrospective    by Charity Majors in Thenewstack

Observability, the development approach or moreover the “movement’” is about three years old and Charity Majors, one of the early pioneers in the field, has decided to take a step back, pan out and “observe” how far it has come. In this article, she takes a closer look at why it formed and why other approaches and methods fall short, citing important contributors along the way. She explains the criticality of adopting observability for any engineering team building and maintaining complex, distributed systems. .....

Like so many other terms in software engineering, “observability” is a term borrowed from an older physical discipline: in this case, control systems engineering. Observability is the mathematical dual of controllability.

“Less formally, this means that one can determine the behavior of the entire system from the system’s outputs. If a system is not observable, this means that the current values of some of its state variables cannot be determined through output sensors.”  .... "