Resource object pattern. This data structure defines a pattern that is used to match resource
objects using a native identifier(s). This may be primary or secondary identifier.
The filter used to match the object. If the object matches then it is regarded to be
protected.
Although this is minOccurs=0 it is a mandatory attribute for all current practical uses.
The minOccurs=0 is here only for compatibility and it will be changed to minOccurs=1
when the deprecated syntax is removed.