(By David Inman): "As described in the What? section, there may be different orders for different possession constructions and/or different noun possession classes. We code for the open class of nouns (sometimes called the alienable class), and if the relative frequencies of available constructions are known, we prefer the most common one. If only information about pronominal possession is available, then this feature is coded as unknown <?>. ❡
The state refers to a single construction which has both orderings or when the grammar explicitly says that two constructions with different orders are equally common or basic. In cases where two different constructions exist for the default class with different orderings of possessor and possessed noun and there is no indication of which is more frequent or basic, we have opted to code this as <?>. ❡
Though the ordering of these constituents is largely determined by the surface structure, there are two particular types of constructions for which we believe and <?> values are most appropriate. These are constructions in which there is an intervening lexical head between the possessor and possessed nouns: clausal possessive constructions and classifier possessive constructions..."