Appendix 3: Standard values for unknown information

Appendix 3 provides a set of standard values that may be used when mandatory property values are not available for various reasons.

Examples of usage:

<creatorName>:unkn</creatorName>

<title>:unas</title>

<publisher>:null</publisher>

Table 3: Standard values for unknown information

Code	Definition
:unac	temporarily inaccessible
:unal	unallowed, suppressed intentionally
:unap	not applicable, makes no sense
:unas	value unassigned (e.g., Untitled)
:unav	value unavailable, possibly unknown
:unkn	known to be unknown (e.g., Anonymous, Inconnue)
:none	never had a value, never will
:null	explicitly and meaningfully empty
:tba	to be assigned or announced later
:etal	too numerous to list (et alia)