a partially ordered set of discourse entities. The partial ordering is defined by some sort of semantic relation, such as part--whole or type--subtype. Example: in the exchange Do you like this album? Yeah, this song I really like, the album mentioned in the first turn and the song mentioned in the second turn are members of a poset which is defined by a part--whole relation (the album is the whole, and the song is a part of the album). (Section 11.2.3)