unit of measurement
Let an agent handle units by quantity, system, definition and conversion, and never report a number without a unit.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
written by Claude from model knowledge without web access - no source was read, every claim is a lead to verify
Researched by: Claude
Purpose and description
Let an agent handle units by quantity, system, definition and conversion, and never report a number without a unit.
A definite magnitude of a quantity, defined and adopted by convention, used as a standard for measurement, such as the metre, kilogram, second or pharmacopoeia units.
What it is for: Making measurements comparable.
It can be convert between units; check dimensional consistency; choose appropriate units; trace units to definitions.
Distinguishing features
Standard magnitude of a quantity
Organised in systems
SI is the international system
Some units are domain-specific
What it looks like
Symbols such as m, kg, s, and names on instruments and labels.
How it is recognised
Unit symbols and names
Systems: SI, imperial, US customary
Special units such as USP units
Related models
measures - quantity
has kind - units
is defined by - system
is used in - practice
In practice
Families and kinds
SI base and derived units
non-SI units accepted with SI
imperial and US customary units
domain units such as pharmacopoeia units
Identifiers
UCUM code code strings machine-readable units
QUDT unit IRI URI semantic units
Standards and regulation
SI Brochure
ISO 80000
Legal metrology law
Failure modes and hazards
Unit conversion errors
Missing units
Confusing similar units
Also called
+272
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 4 bundles · 8 layers · 8 findings · 16 questions.
Definition Which unit.
Units need definitions.
Unit
Name and symbol.
Unit
Unit identity.
- Which unit, with which symbol? definition
- What quantity does it measure? definition
System
SI or other.
System
Unit system.
- Which system does it belong to? definition
- How is it defined? provenance
Conversion Between units.
Conversions must be exact.
Factor
Exact factor.
Factor
Conversion factor.
- What is the exact factor to SI? measurement
- Is it exact or approximate? boundary
Consistency
Dimensions.
Consistency
Dimensional check.
- Are units consistent in the calculation? boundary
- What checks catch errors? action
Use Choosing units.
Choice affects clarity.
Choice
Appropriate units.
Choice
Unit choice.
- Which unit suits this audience and context? action
- Is a legal unit required? boundary
Machine-readable
Codes.
Machine
Unit codes.
- Which UCUM or QUDT code represents it? provenance
- Is it used consistently? boundary
Safety Critical errors.
Unit errors can be dangerous.
Medicine
Dose units.
Medicine
Dose units.
- Are dose units clear, avoiding error-prone abbreviations? boundary
- Which guidance applies? provenance
Engineering
Design errors.
Engineering
Engineering checks.
- Could a unit error cause a failure here? boundary
- How is it prevented? action
What the second pass must settle
- Should units be instances with UCUM codes?
- How should non-SI units be linked?
- The registry entry has merged aliases such as look; should they be removed?