Unified Code for Units of Measure

The Unified Code for Units of Measure ( Ucum ) is a rule-based coding system for units.

Overview

Purpose of this standard is the electronic data exchange of physical quantities. Ucum is closely aligned with international standards ( ISO 2955-1983, ANSI X3.50 - 1986), which in turn are based on the SI unit system. The coding system allows the formulation of compound expressions for arbitrary units derived from the base units. Ucum to combine uniqueness and computational traceability to SI units with practical relevance, readability and applicability.

The OID for the coding system Ucum is 2.16.840.1.113883.6.8. The designated system includes all constructible according to the encoding rules Ucum expressions by definition. The formal definition, code tables and sample implementations can be found on the Ucum pages of the Regenstrief Institute.

Unlike tabulated coding systems ( SNOMED CT, LOINC ) are valid Ucum codes composed of a relatively small number of " atomic" symbols and operators that are combined by simple syntax rules.

The elements of the definition of Ucum are:

  • Basic units: A fixed list of base values ​​for length, mass, time, temperature, electrical charge, light intensity and angle.
  • Prefixes: A fixed list of attachments that can be used as symbols of multipliers (see Resolutions for units, Binärpräfixe ).
  • Derived units (atomic unit symbols ): A defined list of " atomic symbols " are shown in the other units with conversion factors and formulas for the return to base units. Each unit in this list carries an attribute metric / non- metric that determines whether this unit may be combined with a prefix or not.
  • Simple rules for combining the symbols, along with several operators for multiplication, division, exponentiation, and grouping parentheses.

With these rules, an infinite number of valid units are derived ( a table- based approach is inevitably incomplete, however, see list of physical quantities ). The syntax rules, together with the Umrechnungsfakoren contained in the definition table allow automatic and unique translation of physical quantities having the same dimension, which are expressed in different units.

For the transmission of measurements, for example as a result of an investigation or clinical observation, the unit must be specified as Ucum code in HL7 Version 3. In addition to standardized coding of units with Ucum with LOINC is a standard for the identification of measurement and analysis methods.

Some organizations and standards that use Ucum codes recommend or prescribe:

  • HL7
  • DICOM
  • Open Geospatial Consortium
  • FDA - Center for Drug Evaluation and Research
  • Centers for Disease Control and Prevention
  • California Health Care Foundation

Alternative approaches with comparable target direction can be found in the definition of a Metric Interchange Format and in the document POSC RP66 V2 of Petro Technical Open Standards Consortium. However, both definitions do not cover a sufficient extent the conventional units from which are used in the field of medicine and biochemistry today.

American National Standards Institute System of measurement
771068
de