Service Variable #

Formal Definition: A service variable is a mutable attribute of a service state.

Observable, Partially Observable, Hidden #

A service variable can be Observable which means it can be observed all the time by a service observer, Partially Observable if there are instances where it is impossible to observe it by a service observer, or Hidden if it is impossible to observe it by a service observer in all of its instances in a service state.

In practice, service variables are what monitoring observes to infer a service state. Usually, a combination of these service variables' values is enough to infer that a service state is active or inactive.