Chapter 4, Problem 20RQ

Explanation of Solution

Simple phrase of a sentential form:

Phrase in a parse tree is the string of terminals collected from the leaves of the partial parse tree, rooted at one specific internal node in the original parse tree.

• A simple phrase is a phrase which is derived in one single step from a nonterminal node.
• Simple phrases are subsets of a phrase.
• $\beta$ is a simple phrase in the right sentential form $\gamma$ if and only if $\text{S}\Rightarrow \text{*}\gamma$, where, ${\text{γ= α}}_{\text{1}}{\text{Aα}}_{\text{2}}$ and ${\text{α}}_{\text{1}}$