UnitsDB 2.0 — multilingual names, new identifiers, and expanded coverage

We are releasing UnitsDB 2.0, a major update to the authoritative database of scientific units. This release introduces structural improvements, richer metadata, and expanded coverage that make UnitsDB more interoperable and internationally accessible.

Organization-neutral identifiers

Every entity now carries a unitsml type identifier alongside the existing NIST identifier:

identifiers:
  - id: u:meter
    type: unitsml
  - id: NISTu1
    type: nist

These organization-neutral IDs (like u:meter, q:force, d:length) provide stable, namespace-prefixed identifiers that are not tied to any single organization. This makes UnitsDB data portable across systems and easier to reference in linked-data contexts.

Multilingual support

Units and quantities now include names in multiple languages. For the initial release, French translations sourced from the BIPM SI Digital Framework have been added:

names:
  - value: length
    lang: en
  - value: longueur
    lang: fr

This lays the groundwork for supporting additional languages in future releases.

Enhanced symbol representations

Symbols now include six representation formats across entities that use them (units, prefixes, dimensions):

Format	Use case
unicode	Direct rendering in text
html	Web display
latex	Scientific documents
mathml	Mathematical markup
ascii	Plain-text contexts
id	Machine-readable identifiers

Unit scales

A new entity type — scales — has been added to UnitsDB. Scales define the measurement scale properties for units, covering continuous ratio, continuous interval, logarithmic, discrete, and other scale types. Five scale definitions are included in this release.

15+ new quantities and dimensions

UnitsDB 2.0 adds quantities and dimensions from ISO and IEC standards:

• ISO 80000-8: octave and decade for logarithmic frequency range
• IEC 80000-13: erlang (E), baud (Bd), shannon (Sh), hartley (Hart)
• New radiation quantities: fluence, fluence rate, kerma rate, exposure, emission rate
• Temperature quantities: ITS-90 (kelvin and celsius), PLTS-2000
• Phase, relative humidity, fuel efficiency, and more

Structured references

Entities now include formalized references to external authorities:

references:
  - uri: http://si-digital-framework.org/quantities/LENG
    type: normative
    authority: si-digital-framework

References link to authoritative sources like the SI Digital Framework, UCUM, and ISO/IEC standards.

Schema versioning

All YAML files now include a schema_version field, enabling applications to detect and adapt to structural changes between releases.

Data quality improvements

This release includes numerous corrections:

• Fixed dimensional assignments for units that were incorrectly categorized (e.g., pH as acidity, not plane angle; acre as area, not length)
• Sequential quantity identifiers for consistency
• Normalized YAML structure across all files
• Bidirectional verification of dimension ↔ unit and quantity ↔ unit references

Migration from 1.0

Applications using UnitsDB 1.0 will need to update parsers for:

• New schema_version field in all files
• power field (was powerNumerator) in dimensions
• Language-specific name objects ({value, lang}) instead of flat strings
• Expanded symbol representation formats
• New reference structure for external authorities

See the full release notes for complete migration details.

Explore the data

• UnitsDB browser — search and browse all entities interactively
• GitHub repository — download YAML data files
• unitsdb-ruby — Ruby library for programmatic access