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. 1999 Mar-Apr;6(2):151-62.
doi: 10.1136/jamia.1999.0060151.

Units of measure in clinical information systems

G Schadow  1 , C J McDonald, J G Suico, U Föhring, T Tolxdorff
Affiliations

Units of measure in clinical information systems

G Schadow et al. J Am Med Inform Assoc. 1999 Mar-Apr.

Abstract

The authors surveyed existing standard codes for units of measures, such as ISO 2955, ANSI X3.50, and Health Level 7's ISO+. Because these standards specify only the character representation of units, the authors developed a semantic model for units based on dimensional analysis. Through this model, conversion between units and calculations with dimensioned quantities become as simple as calculating with numbers. All atomic symbols for prefixes and units are defined in one small table. Huge permutated conversion tables are not required. This method is also simple enough to be widely implementable in today's information systems. To promote the application of the method the authors provide an open-source implementation of this method in JAVA. All existing code standards for units, however, are incomplete for practical use and require substantial changes to correct their many ambiguities. The authors therefore developed a code for units that is much more complete and free from ambiguities.

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Figures

Figure 1
Figure 1
The grammar of unit expressions in the Backus-Naur-Form.
Figure A
Figure A
Class diagram for an implementation of units: A Measurement has one Unit and a Unit has one Dimension. A UnitAtom is a special Unit that is defined in a table. The database of UnitAtoms and Prefixes are used by the static method Unit : parse to create a new Unit-object from a String representation of the unit. A Unit may have a FunctionPair that is used to convert the nonratio unit to and from its proper unit.
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References

    1. Health Level Seven, version 2.3. Ann Arbor, Mich.: Health Level Seven, 1997.
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    1. Gruber TR, Olsen GR. An ontology for engineering mathematics. In: Doyle J, Sandewall E, Torasso P (eds). Principles of Knowledge Representation and Reasoning. Proceedings of the Fourth International KR '94 Conference; Bonn, Germany; May 24-27, 1994. San Francisco, Calif.: Morgan Kaufmann, 1994. Also available at: http://ksl-web.stanford.edu/knowledge-sharing/papers/engmath.html.
    1. Gruber TR. A translation approach to portable ontology specifications. Knowledge Acquisition. 1993;5(2):199-220. Available at: http://ksl-web.stanford.edu/knowledge-sharing/papers/#ontolingua-intro.
    1. ISO 2955: Information Processing: Representation of SI and Other Units in Systems with Limited Character Sets. Geneva, Switzerland: International Organization for Standardization, 1983.

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