This report provides a basis for evaluating relational programming by presenting an implementation of a moderately complex program using relational programming. The program is a syntax-directed editor, a major component in a programming environment that allows the direct construction, modification, and display (unparsing) of parse trees. Relational programming is ideal for this application, since the relational calculus provides a number of high-level operators for manipulating trees and other complex data structures. The editor is presented in two notations: the usual mathematical notation and a simple natural-language-like notation. (Author)