More recently, Hirschberg and Pierrehumbert (1986) have 176 proposed that final lowering is not a prosodic property specific to a particular phonological phrase level in English, but rather is a more direct phonetic expression of discourse structure. 2.2 Correlation of Segmentation with Utterance Features The segmental structure of discourse has been claimed to constrain and be constrained by disparate phenomena, e.g., cue phrases (Hirschberg and Litman 1993; Grosz and Sidner 1986; Reichman 1985; Cohen 1984), plans and intentions (Carberry 1990; Litman and Allen 1990; Grosz and Sidner 1986), prosody (Hirschberg and Pierrehumbert 1986; Butterworth 1980), nominal reference (Webber 1991; Grosz and Sidner 1986; Linde 1979), and tense (Webber 1988; Hwang and Schubert 1992; Song and Cohen 1991). Phrasing and Accent in English The importance of intonational information to the communication of discourse structure has been recognized in a variety of studies (Butterworth 1975; Schegloff 1979; Brazil, Coulthard, and Johns 1980; Hirschberg and Pierrehumbert 1986; Pierrehumbert and Hirschberg 1990; Silverman 1987). The segmental structure of discourse has been claimed to constrain and be constrained by disparate phenomena: cue phrases (Hirschberg and Litman, 1993; Gross and Sidner, 1986; Reichman, 1985; Cohen, 1984); lexical cohesion (Morris and Hirst, 1991); plans and intentions (Carberry, 1990; Litman and Allen, 1990; Gross and Sidner, 1986); prosody (Grosz and Hirschberg, 1992; Hirschberg and Gross, 1992; Hirschberg and Pierrehumbert, 1986); reference (Webber, 1991; Gross and Sidner, 1986; Linde, 1979); and tense (Webber, 1988; Hwang and Schubert, 1992; Song and Cohen, 1991). 2 Theoretical Foundations In this work, we implement and extend the compositional theory of intonational meaning proposed by Pierrehumbert and Hirschberg (1986; 1990), who sought to identify correspondences between the Bell Laboratories, Lucent Technologies 600 Mountain Avenue Murray Hill, NJ 07974 USA {chn I j encc}research, bell-labs, com Grosz and Sidner (1986) computational model of discourse interpretation and Pierrehumbert's prosodic grammar for American English (1980).