An early machine learning ap- proach to content selection was presented by Jordan and Walker (2000;; they were also interested in an exploration of the validity of different psycholinguistic models of reference production, including Grosz and Sidner's (1986) model of discourse structure, the conceptual pacts model of Clark and colleagues, and the intentional influences model developed by .
their data set consists of only 393 referring expressions, compared to our 16,358, and these expressions had functions other than identification; most importantly, the entities referred to were not part of a shared visual scene as is the case in our data.