“…In contrast to hierarchical structures, item to item structures build structures among observable knowledge item themselves (Falmagne, Koppen, Villano, Doignon, & Johannesen, 1990;Doignon & Falmagne, 1999), bypassing concept links. A number of researchers have worked on the problem of building student models within this framework (Dowling & Hockemeyer, 2001;Kambouri, Koppen, Villano, & Falmagne, 1994). Our own work on Partial Order Knowledge Structures (POKS) (Desmarais, Maluf, & Liu, 1996;Desmarais & Pu, 2005) falls under this line of research as well.…”