the correct join should actually be an OUTER JOIN, not an INNER JOIN.

e.g. if a sort is performed by subtype attribute, most certainly no filtering should be expected. For object of types other than the desired subtype, the attribute should imply become NULL, Predicates may then choose to filter such entries.

Specification above is wrong IMHO and it should be possible (at least by an additional Hibernate flag) to get a OUTER JOIN.