attribute filter RuleReference ?

[Tom Zeller]

Should we remove RuleReference from the attribute filter schema or
leave RuleReference unimplemented as in IdPv2 or should we implement
it for IdPv3 ?

The attribute filter schema for the AND, OR, and NOT match functors
allows a RuleReference element which is unimplemented in the IdPv2
Spring parsers. So, I believe no one is using RuleReference.

Other reference elements such as PermitValueRuleReference are
implemented, and Rod mentioned to me that maybe we should code these
references in a common way.

Thoughts ?