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Do our previous observations mean that we have to give up our idea of systematically translating expressions of natural language into semantic representations? Well, yes and no. Yes, as we have seen before, using straightforward first-order logic gets us into all kinds of troubles. But no, there is a systematic way of translating if we use an intermediate level of semantic representation.
A theory of discourse interpretation that uses such an intermediate level of representation is Discourse Representation Theory (DRT) , a formalism proposed in the early 1980s by Hans Kamp. As we will see, DRT deals with all the problems noted above (and more) in an interesting way. The invention of DRT led to a shift from a ``static'' to a ``dynamic'' view on natural language semantics. To explain certain discourse phenomena, such as the interaction between indefinite noun phrases and (anaphoric) pronouns in texts shown before, the traditional account of considering meaning in terms of truth conditions turned out to be unsatisfactory. DRT adopts the rather `dynamic' view of natural language semantics, where the meaning of a sentence is defined in how it can change the context.
One of the striking features of DRT is that it, instead of working with first-order formula syntax, works with explicit semantic representations. Such a representations is called Discourse Representation Structure (DRS) , and describes the objects mentioned in a discourse and their properties. As we will see shortly, the DRT approach sheds a whole new light on discourse processing and has sophisticated means to deal with discourse anaphora.
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