G22.2590 - Natural Language Processing - Spring 2005 Prof. Grishman
Lecture 11 Outline
April 18, 2003
Syntax-Driven Semantic Analysis
(J&M Chapter 15))
Goal: general rules for producing semantic representations of
sentences (as discussed last week).
Approach: syntax-driven semantic analysis
What should the semantic representation of intermediate nodes look like?
- principle of compositionality
(problem of idioms)
- rule-by-rule hypothesis
- associate a semantic feature (sem) with each node
- associate a semantic rule (in braces) with each node
- problem of VP node
- lambda notation / lambda reduction
- problem of quantified NPs
- complex terms and quasi-logical form (Lecture 10 notes).
simple grammar with semantics (Word file).
Some examples using this grammar ...
- AyCaramba serves meat. (J&M p. 554)
- A restaurant serves meat.
- A cheap restaurant serves meat.
- Mary's restaurant serves meat..
- A restaurant in SoHo serves meat.
Scoping resolution: converting
form to logical form (with conventional quantifier scope)
Factors in resolving scope:
‘strength’ of different quantifiers
“each”, in particular, has wide scope
order of quantifiers
(“Some students were rejected by every college.” vs. “Every college
definite NPs evoking functional relationships
(“Every patient had an X-ray.” vs. “An X-ray was taken of every
more generally, semantic knowledge
(“This train does not stop at every station.”)
Strategies for data base query applications
Assuming queries are full grammatical sentences:
(we will consider how to handle fragmentary queries as part of
Convert to quasi-logical form
Resolve scoping, generating logical form
Interpret logical form as data base query:
non-reified predicates access relations of data base
[in reified forms, event variables iterate over rows of
restricted quantifiers become iterations over sets of data base elements
[checking for non-empty sets: presupposition
- WH quantifiers print results
[quantifiers outside WH quantifier generate tables]