EntityRoleWhiteList metadata filter

[Tom Scavo]

Apparently a MetadataFilter of type EntityRoleWhiteList [1] may be
empty, that is, it may contain zero <RetainedRole> child elements:

<MetadataFilter xsi:type="EntityRoleWhiteList">
    <!-- no child elements -->
</MetadataFilter>

That would seem to imply that no entities are retained. Is that the
correct interpretation?

OTOH, if no child elements means that ALL entities are retained, then
I claim that's a contradiction since *adding* <RetainedRole> child
elements eventually leads to the same result.

Suppose the filter required at least one <RetainedRole> child element
instead. Not only is that more clear but in that case attribute
removeRolelessEntityDescriptors becomes unnecessary since entities
with no roles would positively not be retained.

Btw, is an entity with an AffiliationDescriptor child element defined
to be a "roleless" entity descriptor? If so, all such entities would
be removed by default. Is that what happens?

Tom

[1] EntityRoleWhiteListFilter https://wiki.shibboleth.net/confluence/x/_gInAQ