Problem 13
How do the results of parsing the following two sentences differ? How do the results of semantic analysis differ? An awesome sunset was seen by Andrea. Andrea saw an awesome sunset.
Problem 14
How do the results of parsing the following two sentences differ? How do the results of semantic analysis differ? If \(X<10\), then subtract 1 from \(X\) else add 1 from \(X\). If \(\mathrm{X}>10\), then add 1 to \(\mathrm{X}\) else subtract 1 from \(X\).
Problem 15
In the text, we briefly discussed the problems of understanding natural languages as opposed to formal programming languages. As an example of the complexities involved in the case of natural languages, identify situations in which the question "Do you know what time it is?" has different meanings.
Problem 17
Draw a semantic net representing the information in the following paragraph. Donna threw the ball to Jack, who hit it into center field. The center fielder tried to catch it, but it bounced off the wall instead.
Problem 18
Sometimes the ability to answer a question depends as much on knowing the limits of knowledge as it does on the facts themselves. For example, suppose databases A and B both contain a complete list of employees who belong to the company's health insurance program, but only database \(\mathrm{A}\) is aware that the list is complete. What could database A conclude about a member who was not on its list that database B could not?
Problem 21
In the context of a production system, what is the difference between a state graph and a search tree?
Problem 23
a. Suppose a search tree is a binary tree and reaching the goal requires eight productions. What is the largest number of nodes that could be in the tree when the goal state is reached if the tree is constructed with a breadth-first manner? b. Explain how the total number of nodes considered during the search could be reduced by conducting two searches at the same time-one beginning at the initial state while the other searches backward from the goal-until the two meet. (Assume that the search tree recording the states found in the backward search is also a binary tree and that both searches progress at the same rate.)
Problem 24
In the text, we mentioned that a production system is often used as a technique for drawing conclusions from known facts. The states of the system are the facts known to be true at each stage of the reasoning process, and the productions are the rules of logic for manipulating the known facts. Identify some rules of logic that allow the conclusion "John is tall" to be obtained from the facts that "John is a basketball player," "Basketball players are not short," and "John is either short or tall."
Problem 26
Analyze the game of checkers as a production system and describe a heuristic that could be used to determine which of two states is closer to the goal. How would the control system in this setting differ from that of a one-person game such as the eight-puzzle?
Problem 28
Draw the search tree that is generated by a breadth-first search in an attempt to solve the eight-puzzle from the following start state without using the assistance of any heuristic information. $$ \begin{array}{|l|l|l|} \hline & 1 & 3 \\ \hline 4 & 2 & 5 \\ \hline 7 & 8 & 6 \\ \hline \end{array} $$
