One measurement, end to end
Pendrill's Table 1.1 describes a four-level hierarchy across three parallel axes. This walkthrough makes every cell clickable — the classes that model it, and the worked example instance that realizes it: the length of a rod, measured.
| Level | QuantityDybkaer (2010) | Entityphenomena, bodies, substances | MeasurementPendrill (2019) |
|---|---|---|---|
| 0 | kind of quantity space The most abstract grouping — quantities sharing a dimension, comparable and addable. | — | — |
| 1 | quantity, Q = X length A named, defined concept — the level ISO/IEC 80000 publishes. | kind of entity physical body The abstract category of things quantities can characterize. | — |
| 2 | dedicated quantity (Sachgrösse) length of rod A quantity bound to an entity — coined by Fleischman (1960). | entity rod A specific type of physical thing the dedicated quantity is about. | — |
| 3 | instantiation of an entity quantity length of rod AB, today at 09:15 A particular quantity of a particular entity instance at a particular time. | instantiation of an entity rod AB, today at 09:15 The particular physical object that exists in reality. | quantity as measured, Qm = {Q}·[Q] 1.234 m ± 0.001 The measurement result — numerical value × unit, with uncertainty (GUM). |
Empty cells are Pendrill's own: only the quantity axis reaches level 0, and the measurement axis exists only at level 3.
Follow the measurement
The same chain the table describes, as data — each step is a live page.