Levels of representation in discourse relations

Most schools of linguistics have their foundations in a study of the syntax and semantics of individual sentences. Cognitive linguistics is to some extent no exception: while it has always devoted considerable attention to the conceptual aspects of linguistic meaning and to the study of language in use, the focus of research has still traditionally been on single sentences or propositions rather than on larger units of text and discourse. However, within many schools of linguistics, a signi®cant body of work on discourse structure has developed over the last ®fteen years or so. Discourse-oriented studies in cognitive and functional linguistics include research on the discourse function of syntactic constructions such as subordinate clauses (Tomlin 1985; Matthiessen and Thompson 1987; Ramsay 1987) as well as on the need for functional and usage-based analyses of discourse (Langacker 2001; Barlow and Kemmer 2000). Discourse-oriented work in formal linguistics centers around the in ̄uential dynamic semantic theories of Kamp and Heim (see, for example, Kamp and Reyle 1993), Heim (1982), and latterly Veltman (1996), which focus on issues relating to anaphora and presuppositions. In computational linguistics, there is a growing body of work on the interpretation and generation of extended texts; see, for instance, Lascarides and Asher (1993) or Strube and Hahn (1996) for discourse interpretation, and Hovy (1993) or Marcu (1997) for discourse generation. Interestingly, at the discourse level, the dividing line between cognitive linguistic approaches and traditional approaches seems less clear cut than at the sentence level. Many of the controversial proposals in cognitive linguistics concern the status of sentence syntax, in particular the question of whether syntax is an autonomous and purely formal level of representation (cf. Langacker 1986; Jackendo€ 1996). However, it is widely accepted that purely formal or syntactic principles play a far smaller role