Semantics and Logical Form

Notes from Allen, Ch. 8

• Logical Form
  Logical form is a context-independent meaning representation (analysis does not require interpretation of the sentence in context). This is a useful simplifying assumption, but does not treat certain kinds of natural language utterances (e.g., speech acts).

• Meaning vs. Usage.
  Allen posits two levels of semantic representation (logical form, which is context-independent, and the final representation (which is context-dependent); see Figure 8.1.

• Example: Indexical Terms
  Sentences like "The red ball dropped" can have many different final representations, depending on which particular red ball is being referred to. Definite NPs like 'the red ball' are indexical terms -- terms whose final meaning requires assigning an 'index' or pointer to indicate exactly which object we are referring to.

• Discourse Context
  In any conversation or text, asume there is a discourse situation that records the information conveyed so far (implication: indexical terms refer to items previously introduced in the discourse). Logical form can then be thought of as a function which maps the previous discourse context and a new utterance to an updated discourse context (see Figure 8.2).