# description
Identifies the style of unique identifier used to identify a namespace.

# concept[].definition
An ISO object identifier; e.g. 1.2.3.4.5.

# concept[].definition
A universally unique identifier of the form a5afddf4-e880-459b-876e-e4591b0acc11.

# concept[].definition
A uniform resource identifier (ideally a URL - uniform resource locator); e.g. http://unitsofmeasure.org.

# concept[].definition
Some other type of unique identifier; e.g. HL7-assigned reserved string such as LN for LOINC.