5. Qualifiers

Qualifiers are additions to the metadata elements that provide information about how the semantics (meaning) of an element have been refined, or about how the value (specific content) of an element should be interpreted.

The guiding principle for using qualifiers with NZGLS elements, colloquially known as the 'Dumb-Down Principle', is that a client (e.g. a person or software) should be able to ignore any qualifier and use the description (element content) as if it were unqualified. The remaining element value without the qualifier should continue to be generally correct and useful for discovery and other management purposes.

NZGLS uses two types of qualifier:

Element refinements:

Element refinements refine the semantics (meaning) of the element by further specifying the relationship of the element value to the resource itself. A refined element shares the meaning of the unqualified element, but with a more restricted scope. For example, the element Coverage can refer to legal or administrative scope (jurisdiction), to the geographical scope (spatial), or to the period of time covered by the resource (temporal).

The element refinements that may be used in NZGLS are listed in the description of each element. It is expected that the element refinements will continue to be added to over time, but that these changes will not generally affect existing refinements. The NZGLS metadata set will be modified from time to time to specify the element refinements that may be used for each element. Please check the NZGLS website (http://www.nzgls.govt.nz/) for updates.

Encoding schemes:

Encoding schemes indicate how the value of an element is to be interpreted if it has been chosen from a controlled vocabulary, or is encoded if an externally defined standard is used. A value expressed using an encoding scheme will be either selected from a controlled vocabulary (e.g. a term from a classification system or set of subject headings) or a string formatted in accordance with a formal notation (i.e. YYYY-MM-DD as the standard expression of a date, e.g. 2000-01-21). This standard is not prescriptive about available encoding schemes for particular elements and does not attempt to specify available schemes for each element. Most elements in the NZGLS element set may be qualified with an encoding scheme.

It is assumed that metadata instances based on this standard will specify the encoding scheme used for any element where this is appropriate. The standard identifies best practice encoding schemes, and it should be noted that in particular implementation environments specific encoding schemes may be mandatory.