Type
Type of reference
Metadata: the referenced item is a CMDI metadata document that
describes
one or more resources
Resource: the reference item is a resource that can be accessed directly through the specified URI
Reference
A PID or other type or URI identifying or locating the resource or metadata file
Label
An optional label for this reference providing a short description of the item, to be shown instead of or in addition to the URI
Description
An optional, more detailed description of the referenced item