Requisite Variety (Ashby)
The control system needs as much variety as the environment it controls; otherwise, it fails on exceptions.
In one sentence
A law of cybernetics: a control system needs as much variety as the environment it controls. Application in the Cognitive Enterprise: the agents’ capacity, combined with gates and evals, needs to cover the actual variety of business cases; otherwise, the system fails on exceptions.
Before
Actual variety of business cases
What it does
Control system capacity
After
Covers the variety, or fails on exceptions
Example
The suite covered a letter in Portuguese, a child in school, and a complete report. Reality brought Spanish, a child out of school, a report with an unreadable photo, and a child with two records.
The common case worked. The system failed on the others because its variety was lower than that of the world it had to control.
The common mistake
Measuring quality only on the average case. The system usually breaks in the tail, in rare cases. If the golden dataset does not carry the actual variety of the business, the eval is measuring what is easy to measure.
In practice
- List the types of exception the real process produced in the past year.
- Check how many are in the answer key. The difference is your exposure.
- Every new exception becomes a case. That way, the system’s variety keeps pace with the world’s.
How to make it tangible
List the types of exception the real process produces and check whether the answer key covers them.
Connects with
Translated from Portuguese with AI assistance.