None

None indicates that a property of page type has no value. This usually means that the property does not apply. It is not the same as unknown, which means that the property might apply in this case but the value is not known. If the property ought to have a value but it can't reasonably be known, use not found instead.

Examples of when to use None:

• Property:Signed by if a document is not signed by anyone
• Property:Is version of in Form:Serial publication if there is only one version of the serial and it does not need to be grouped into a parent work