Introduction to RST (Rhetorical Structure Theory) Kezban Demirtaş Başıbüyük

References Mann, William C. and Sandra A. Thompson. (1988). Rhetorical Structure Theory: Toward a functional theory of text organization. Text, 8 (3), 243-281. Taboada, Maite and William C. Mann. (2006). Rhetorical Structure Theory: Looking back and moving ahead. Discourse Studies, 8 (3), 423-459. http://www.sfu.ca/rst/ http://www.sfu.ca/rst/pdfs/RST_Introduction.ppt

Outline What is RST? Principles Components Relations Observers and Definitions How to do an RST Analysis Summary

What is RST? RST is a theory of text organization. It was developed in the 1980s at the Information Science Institute of the University of Southern California. RST addresses text organization by means of relations that hold between parts of text. RST offers an explanation of the coherence of texts by postulating a hierarchical, connected structure of texts.

Principles Coherent texts consist of minimal units, which are linked to each other, recursively, through rhetorical relations. Rhetorical relations also known, in other theories, as coherence or discourse relations. Coherent texts do not show gaps or non-sequiturs. Therefore, there must be some relation holding among the different parts of the text.

Components Units of discourse Nuclearity Relations among spans Texts can be segmented into minimal units, or spans. All units are also spans, and spans may be composed of more than one unit. Nuclearity Some spans are more central to the text’s purpose (nuclei), whereas others play secondary role (satellites). Relations among spans Spans are joined into discourse relations Hierarchy/recursion Spans that are in a discourse relation may enter into new relations.

Relations They hold between two non-overlapping text spans. Most of the relations hold between a nucleus and a satellite. But there are also multi-nuclear relations. A relation consists of: 1. Constraints on the Nucleus, 2. Constraints on the Satellite, 3. Constraints on the combination of Nucleus and Satellite, 4. The Effect.

Nucleus::Satellite Relation In this relation, a claim is followed by the evidence for the claim. Claim is more essential to the text than the particular evidence so the claim span is called a nucleus and the evidence span is called a satellite. As an example;

Multinuclear Relation If a relation does not have a particular span of text which is more central to the author’s purposes, it is called Multinuclear. In the example, two alternates of contrast relation have equal importance for the text.

Graphical Representation A horizontal line covers a span of text (possibly made up of further spans). A vertical line signals the nucleus. A curve represents a relation, and the direction of the arrow, the direction of satellite towards nucleus. .

Lactose Example Let’s look at the relations of a text. The following text has been broken into 5 units for analysis.

Relation Types Relations are of different types Subject-Matter relations : they relate the content of the text spans Cause, Purpose, Condition, Summary Presentational relations : more rhetorical in nature. They are meant to achieve some effect on the reader Motivation, Antithesis, Background, Evidence

Relation names (in M&T 1988) The set of relations is in principle open, but the set above, defined in Mann & Thompson 1988, has proven effective for many purposes.

Observers and Definitions RST is designed to enable the analysis of texts. There is a graphical convention for expressing the structures of texts as we have seen just before. But the particular claims made by the analyst can be made explicit based on the definitions of the relations. For all relations in a text, observers are expected to give definitions of relations. An example of typical relation definition is given below;

Example: Evidence Constraints on the Nucleus The reader may not believe N to a degree satisfactory to the writer Constraints on the Satellite The reader believes S or will find it credible Constraints on the combination of N+S The reader’s comprehending S increases their belief of N Effect (the intention of the writer) The reader’s belief of N is increased

How to do an RST Analysis Divide the text into units Unit size may vary, depending on the goals of the analysis Typically, units are clauses Examine each unit, and its neighbours. Check if “Is there a clear relation holding between them?” If yes, then mark that relation (e.g., Condition) If not, the unit might be at the boundary of a higher-level relation. Look at relations holding between larger units (spans) Continue until all the units in the text are accounted for Remember, marking a relation involves satisfying all 4 fields (especially the Effect). The Effect is the plausible intention that the text creator had.

Some Issues Problems in identifying relations Definitions of units Judgments are plausibility judgments. Two analysts might differ in their analyses. Definitions of units Vary from researcher to researcher, depending on the level of granularity needed. Relations inventory Many available Each researcher tends to create their own, but large ones tend to be unmanageable.

Summary RST provides an analysis for any coherent carefully written text. Such an analysis provides a motivated account of why each element of the text has been included by the author, Because of its specification of the role of the observer, it provides a basis for statements about the objectivity and subjectivity of the analysis. It also provides a functional basis for studying the discourse-relevant specific forms in texts, "discourse markers" and other formal correlates of discourse structure. Where RST posits structure within sentences, it provides a basis for studying the functions of various forms of clause combining, and more generally the relationships between these sorts of discourse structure and various cohesive devices.

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