Rhetorical Structure Theory

An approach to text structure which is appropriate for muti-sentential, monologic texts.

It has the following features:

• Assumes that a text is divided hierarchically into units
• The units are assymetrically related by a named rhetorical relation: usually a nucleus and a satellite, sometimes two satellites
• Relations derive from speaker goals, with satellites being more central to the goals than satellites
• There is a smallish (around 20), fixed, universal set of relations
• Relations may be grammatically marked (usually by conjunctions: "but", "then" etc.) or simply inferred

This model was developed for text generation and has been widely used there and also in information retrieval applications; there is also some evidence that RST relations have some cognitive reality.

Some relations:

Antithesis: Writer compares two contrasting options, and indicates positive regard for one of them.
S: Rather than winning them with arms,
N: we'd win them with our example.

Concession: The writer acknowledges a potential or apparent incompatibility between the propositions presented in the nucleus and the satellite; the writer recognizes the propositions as compatible; the writer wants the reader to have positive regard for (believe, do) the proposition contained in the nucleus.
N: Although Dioxin is toxic to certain animals,
S: evidence is lacking that it has any serious long-term effect on human beings.

Condition: The satellite presents a situation which is necessary for the nucleus to obtain.
S: If you slowly pour the powder into the fluid,
N: the mixture will be very thick.

Elaboration: The satellite presents additional detail about some element of the nucleus, for instance: members of a set, parts of a whole, instances of a generalization, attributes of an object, steps in a process.
N: Karen is so photogenic.
S: Her smile is perfect.

Evidence: Satellite presents evidence that nucleus is true; reader believes satellite and writer wants reader to believe nucleus.
N: They're having a party next door.
S: I couldn't find a parking space.

Justification: Satellite justifies the writer's inclusion of the nucleus.
S: You look hungry.
N: There's some food in the fridge.

Motivation: Satellite presents information which should make the reader want to perform the action in the nucleus.
N: Take Bufferin.
S: The buffering component prevents excess stomach acid.