Towards Stratification Of RST

Moore and Pollack have recently given an analysis of R.ST relations in tel'mS of in tent ional versus in format ional levels of discourse [5]. Accol'ding to their (convincing) analysis, presentational RST relations correspond to the intentional level of discourse and subject matter relations to the inlbrmational level. For each text there shouhl exist two RST analyses: one containing only presentational relations and the other containing only subject matter relaLtions. Mann and Thoinpson had discussed multiple analyses in RST (Ill, l)P. 2(i-30), stating that a presentational analysis is the only analysis when l)oth presentational and sul)ject-matter relation definitions are satisfied between a given pair of text spans. In their view, the l)resentational analysis is chosen as correct since it describes the changes in the bearer's system of belie£s, i.e. provides deeper insights into discourse goals. Moore and Pollack, however, argue that these two a.nalyses should not compete; instead, "a complete model of discourse structure lnust maintain both levels of relation". In this paper we take this argument one sma.ll step further and suggest a way these two levels might be organized into a stratified structure. Our discussion here ha.s a very narrow focus anti does not a t tempt to answer such iml)ortaut (luestions a.s whether the RST collection of presentational relations is exhaustive and adequate [br describing a.ll possible lilt(rational structures.