Aggregate data — measurements grouped by stage, zone, shift or team rather than attributed to an individual. The default in these notes, and the arrangement that answers almost every operational question.
Common cause variation — the ordinary spread a stable process always produces. Reduced only by changing the process, not by reacting to individual points.
Constraint — the stage that sets the pace of the whole flow. Improving any other stage adds queue rather than output.
Cycle time — elapsed time for one unit from a defined start to a defined end. Distinct from throughput, and improving one can worsen the other.
Dwell — time a tag, item or person remains in a zone. The main output of positioning systems and the input to congestion analysis.
Elapsed time decomposition — splitting total time into waiting, travel, handling, checking and rework. The single most informative analysis available from existing data.
Leading indicator — a measure that moves before harm occurs: near-miss reports, detected proximity events, discomfort reports. As opposed to injury rates, which are too rare and too late to steer by.
Purpose limitation — the commitment that data collected for one stated reason is not used for another. The boundary most often crossed, and the crossing that destroys reporting.
Slotting — the assignment of items to storage locations. The main lever on travel, and an ongoing activity rather than a project.
Special cause variation — a change with an identifiable reason, distinguishable from ordinary spread by falling outside the normal range or by a run or trend.
Standard — an expected time for a task, used for planning and costing. Becomes a quota when applied to individuals with consequences, which is where the injury risk enters.
Touches — the number of times an item is handled between receipt and despatch. Every touch is cost and risk.
Work in progress — work released to the floor and not yet complete. Releasing more of it increases cycle time without increasing throughput once the constraint is saturated.
Terms used loosely elsewhere
"Productivity" is used for output per person, output per hour and output per unit of cost, which behave differently. These notes name the specific measure.
"Real-time" describes both a dashboard refreshed every minute and a system that alerts within a second. The decision being supported determines which is needed, and usually it is neither.
"Utilisation" reported as an annual average conceals both peak shortage and trough surplus. These notes report it by hour.
"Monitoring" covers process measurement, asset telemetry and worker surveillance. These notes distinguish them, because the obligations and the failure modes differ completely.
"Optimisation" frequently means increasing pace. Said plainly, it is easier to check whether the safe method survived it.
Terms deliberately avoided
Several common terms in this field are not used in these notes, for reasons worth stating.
"Labour productivity" attributes system performance to people. These notes name the specific measure and the level it applies at.
"Engagement" as a monitoring output describes an inference that should not be drawn from movement or video data.
"Best practice" conceals whose practice and in what facility. These notes state the trade-off instead.
"Real-time visibility" describes a feature rather than a decision. The decision determines the frequency needed, and it is usually not real time.
"Digital twin" is used for anything from a floor plan to a simulation, and it obscures what is actually being modelled.
How to read these notes
A short orientation for anyone arriving at the collection rather than at one page.
Start with the foundations if the subject is new, particularly the note on measuring the right thing.
Start with the measures section if you have data and no findings.
Start with the workers section if any individual measurement is proposed, and read it before the technology.
Start with common failures if a deployment has stalled.
The reference section states the boundaries — what the data cannot tell you, where the rules come from, and what a working arrangement looks like.
None of it is legal advice, and the notes say so where it matters.