Measurement Package

6.1 Overview

The Measurement package defines a minimum of semantics relating to quantitative measurement, units, and conversion, enabling the Quantity package of the openEHR Data Types Information Model to be correctly expressed. As for the Terminology package, a simple service interface is assumed, which provides useful functions to other parts of the reference model. The definitions underlying measurement and units come from a variety of sources, including:

• CEN ENV 12435, Medical Informatics - Expression of results of measurements in health sciences (see ​http://www.centc251.org );
• the Unified Code for Units of Measure (UCUM), developed by Gunther Schadow and Clement J. McDonald of The Regenstrief Institute (available in HL7v3 ballot materials; ​http://www.hl7.org).

These of course rest in turn upon a vast amount of literature and standards, mainly from ISO on the subject of scientific measurement.

6.2 Service Interface

A simple measurement data service interface is defined according to ​FIGURE 7 , enabling quantitative semantics to be used formally from within the Reference Model. Note that this service as currently defined in no way seeks to properly model the semantics of units, conversions etc - it provides only the minimum functions required by the openEHR Reference Model.

measurement

MEASUREMENT_SERVICE

is_valid_units_string (units: String): Boolean units_equivalent (units1, units2: String): Boolean

FIGURE 7 rm.support.measurement Package
6.2.1	Class Definitions
6.2.1.1	MEASUREMENT_SERVICE Class

CLASS	MEASUREMENT_SERVICE
Purpose Functions	Defines an object providing proxy access to a measurement information service. Signature Meaning
is_valid_units_string (units: String): Boolean require units /= Void True if the units string ‘units’ is a valid string according to the HL7 UCUM specification.

​Editors:{T Beale, S Heard}, {D Kalra, D Lloyd} ​Page 61 of 67 Date of Issue:​08 Apr 2007

© 2003-2006 The openEHR Foundation email: info@… web: http://www.openEHR.org

Measurement Package ​Support Information Model Rev ​1.6.0

CLASS	MEASUREMENT_SERVICE
units_equivalent (units1, units2: String): Boolean require units1 /= Void and then is_valid_units_string(units1) units2 /= Void and then is_valid_units_string(units2)		True if two units strings correspond to the same measured property.
Invariants

Date of Issue:​08 Apr 2007 ​Page 62 of 67 ​Editors:{T Beale, S Heard}, {D Kalra, D Lloyd}

​© 2003-2006 The openEHR Foundation email: info@… web: http://www.openEHR.org

​Support Information Model Definition Package Rev ​1.6.0