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Using STN Units within Z39.50

Z39.50 is an American National Standard that specifies an interoperable protocol and services for information search and retrieval. The Z39.50 protocol specifies formats and procedures governing the exchange of messages between a client and server, enabling the client to request that the server search databases for information that meets specified criteria, and to retrieve some or all of the identified information.  

Within the Z39.50 protocol, units of measure are expressed using the following ASN.1 definition for Unit and IntUnit:

	Unit ::= SEQUENCE{
	     unitSystem      [1] InternationalString OPTIONAL,
	     unitType        [2] StringOrNumeric OPTIONAL,
	     unit            [3] StringOrNumeric OPTIONAL,
	     scaleFactor     [4] IMPLICIT INTEGER OPTIONAL}

IntUnit is simply an integer value together with a unit, and is defined as:

	IntUnit ::= SEQUENCE{
	    value      [1] IMPLICIT INTEGER,
	    unitUsed   [2] IMPLICIT Unit}

In the above definition:

	Unit System provides the context for the unit type and unit.
	Systems in common use in the scientific and technical communities
	include SI, MKS, CGS, FPS, ENG, and STN.  In addition to existing
	standard unit systems, the unit system 'z3950' will be used to
	register those unit types/units needed by implementors and not
	defined by other known systems.  Values of unit type and unit under
	the system 'z3950'will be maintained by the Z39.50 Maintenance
	Agency.

	Unit Type is, for example, 'Mass'.

	Unit is, for example, 'Kilograms' (when unit type is 'Mass').

	Scale Factor is an integer scale factor, base 10.  For example, 9
	would mean that the actual value is the given value times 10 to the
	9th power.

When using STN Units within Z39.50, the following conventions will be followed:

	     unitSystem = "STN"
	     unitType   = STN Unit Type (eg, "length")
	     unit       = STN unit (eg, "meter")

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For further information on the Z39.50 standard, see the Z39.50 Maintenance Agency Home Page.

For further information on using Units within Z39.50, see the Z39.50 Maintenance Agency information on the Z39.50 Maintenance Agency Home Page.