I've spent the last few weeks (lots of plane trips) reading Pragmatics by Levinson et al. Pragmatics is a difficult to define field (like many :P), but from a linguistic perspective, it is roughly "the study of the ability of language users to pair sentences with contexts in which they would be appropriate." (pg 24)
The book talks about five aspects of pragmatics:
- Deixis: methods of directly encoding context into language; "Meet me here a week from now with a stick about this big." (pg 55) Without knowing the context, we cannot know the meanings of me, now (and hence a week from now), this big. Diectic pronouns are pronouns that reference speaker- and hearer-known context.
- Implicature: Grice's theory says that a speaker should: be cooperative, be truthful (quality), be informative (quantity), be relevant, and be perspicuous (manner: avoid obscurity and ambiguity, be brief and orderly). (pgs 101-102) This theory is insufficient, but useful. Implicature also includes notions of quantification (perhaps, some, many, etc.) and metaphors.
- Presupposition: roughly describes that which is immediately inferrable but not the new information in an utterance. Eg., "Sue cried before she finished her thesis" presupposes that Sue finished her thesis, but this is not the new information (which is that she cried). (pg 187) There are both semantic and pragmatic presuppositions; the latter involve shared knowledge between speaker and hearer. (For fun, compare "Sue died before she finished her thesis.")
- Speech Acts: a speech act is a statement that does something rather than just one that says something (eg., "I declare war on Zanzibar." (pg 228)). The basic question of speech acts seems to be that of identifying them and understanding how they differ from normal statements.
- Conversational Structure: analysis of the sequential (and anti-sequential) nature of conversations, interruptions, etc.
One immediate question is whether there is an appliation that demands pragmatic understanding (or, say, understanding of pragmatic implicature and presupposition). This, I'm not sure. I'm curious how divergent pragmatic issues are crosslingually. My hunch is "not much" which implies that this is not necessary for translation purposes (though Czech morphologically encodes for the new/old distinction). IR and IE also seem impervious to the pragmatic hammer. I can come up with artificial situations that suggest QA might benefit, but I feel these are too artificial (i.e., "Did Sue finish her thesis?"). Even summarization seems fairly robust to a lack of pragmatic understanding, although the "new/old" issue is important here. Perhaps what is old in the real discourse is not new for the reader of the summary. But if it just comes through as presupposition, it's unclear that anything is lost. I'm at something of a loss here, because it seems like human conversation has pragmatic influences so deeply embedded that it is surprising that I feel we can do without them for NLP problems.