Uniform Resource Name - Syntax

Syntax

RFC 2141 (dated May 1997 and still classified as requests discussion and suggestions for improvements) describe in BNF the syntax of URNs as:

::= "urn:" ":"

rendered as:

urn::

where is the namespace identifier, and is the namespace-specific string. Phrases enclosed in quotes are Required. The leading "urn:" sequence is case-insensitive. The namespace identifier NID determines the syntactic interpretation of the namespace-specific string.