The centring

Where the process output sits relative to the middle of the tolerance.

The part

What it is

Centring and spread are separate problems with separate fixes. A process running off-centre can be adjusted; a process with too much spread cannot.

Distinguishing them prevents the common response of tightening control on a process that is simply mis-set.

The smallest level

The attributes it carries

Each attribute is one of the framework’s shared types. What a date is, and how it is written, is defined once for the whole model — the note here says what it means in this particular place.

Process mean
Where output centres.
Measure shared type
Target
The middle of the tolerance.
Measure shared type
Offset
The distance between them, which is separately correctable.
Measure shared type