## Introduction to Artificial Intelligence: Problem Set 4

Assigned: Feb. 12
Due: Feb 21 (Feb. 19 is a holiday)

## Problem 1:

For each of the ambiguities listed below, explain how it can be disambiguated using either selectional restrictions, frequency in context (for lexical ambiguity), or world knowledge. If disambiguation is possible using selectional restrictions, you should prefer this to the other two, as selectional restrictions are usually both stronger and easier to implement. If you use selectional restriction, explain what are the features, the relation, and the constraint involved. If you use frequency in context, explain how the context is established by other parts of the sentence. If you use world knowledge, explain the rules being used. For example:

• "The bat ate its dinner" [= flying mammal rather than wooden club]. Answer: Selectional restrictions. The subject of ``ate'' must be ANIMATE: ``wooden club'' is not ANIMATE.
• ``I went up to the door of the house with the red shutters'' [``with the red shutters'' is attached to ``house'' not ``door'' or ``went''.] Answer: World knowledge. Shutters are part of a house, not part of a door. It is unusual to go places carrying shutters.
• ``In the seventh inning, the pitcher was replaced''. [``pitcher'' = baseball player rather than container.] Answer: Frequency in context. The word ``inning'' establishes the context as baseball.

Problems:

• A. President Bush proposes to cut taxes on inheritances because they are too high. ("proposes" = "formally suggests" rather than "offers marriage"; "cut" = reduce rather than literally slice; "they" = taxes rather than inheritances; "high" = a large amount of money rather than literally elevated.)
• B. Emily cuts Anne whenever they meet, because she was once noisily drunk at Emily's dinner party. ("cuts" = deliberately ignores. "she" = Anne. "was ... drunk" = "was intoxicated" rather than "was imbibed.")
• C. Sam hurt Joe with a baseball bat. ("hurt" = "caused pain" or "injured")
• D. The baseball bat hurt Joe. (Why would it important in semantic processing to distinguish this from the meaning in sentence (C)? What disambiguation strategy can be used?)
• D. Joe's head hurts him. ("hurts" = "is in pain")
• F. Sam hurt Joe with his rude remarks about his clothes. ("hurt" = "upset the feelings of"; first "his" = Sam. second "his" = Joe.)
• G. Joe hurt his chances of getting the job by showing up an hour late to the interview. ("hurt" = diminished.)