A resource name can be directly specified (a literal string), a string generated through a mask, or a combination of both. Regardless of the format chosen, the resulting resource name must be unique within the authority path to which it belongs.
A literal string is a constant set of characters for a resource name. Requesting a literal string means to fully specify the resource name that will be assigned to the digital object. An example of a literal string would be a local accession number used as the resource name.
For example, if a still image being deposited has the local accession number sb8897, the resource name portion of the persistent identifier could be specified as:
urn-3:FHCL:sb8897
A URN mask is a placeholder that will be replaced with actual values by NRS. Mask fields may be added anywhere in the string and repeated. They are enclosed in braces { } to distinguish them from other parts of the string. The brace characters are not otherwise valid in a persistent identifier.
The URN mask fields defined in NRS are:
Field | Replacement Value | Meaning |
{dd} | 01-31 | Current day of the month |
{hh24} | 01-24 | Current hour, 24 hour clock |
{mo} | 01-12 | Current month |
{n} | 0-1027 | Unique integer value |
{ss} | 00-59 | Current second |
{yyyy} | 1999-9999 | Current year |
Note that using a mask does not guarantee that the resulting string will be unique. If a non-unique value is generated, an error will result and a persistent identifier will not be created in NRS. To guarantee the generation of a unique persistent identifier, include the integer value {n} in the mask.
For example:
Specified Identifier | Created Identifier |
urn-3:HUL:{n} | urn-3:HUL:75 |
urn-3:FHCL:{yyyy}-{n} | urn-3:FHCL: 1999-76 |
urn-3:FHCL.Loeb:{yyyy}{mo}{dd} | urn-3:FHCL.Loeb:20020103 (unique only for one object on any given day) |
urn-3:FHCL.Loeb:{yyyy}{mo}{dd}{n} | urn-3:FHCL.Loeb:2002010312345 (always unique) |