Chapter 3, Problem 5RQ

Explanation of Solution

Differences between a sentence and a sentential form:

A sentence is a sentential form that has only terminal symbols. By terminal symbols we mean literal symbols that can appear in the inputs to or outputs from the creation rules of a new formal grammar that won’t change as per normal grammar rules.

To understand suppose a grammar that is defined by two rules:

A can become AB

A can become BA

Here ‘B’ is a terminal symbol because no rule exists that would change it to something else. On the other hand, ‘A’ has two rules that can change it, so it is nonterminal...