This report provides a collection of definitions for the semantics of sub-trees and contexts as manipulated by standard sub-tree crossover in genetic programming (GP). These definitions allow us to completely and compactly describe the exact semantics of the components manipulated by sub-tree crossover, and the semantic results of those interactions. Sub- sequent work shows how these definitions can be used to collect valuable data about the available diversity in a GP population and the opportunities available to sub-tree crossover.
McPhee, Nicholas Freitag; Ohs, Brian; and Hutchinson, Tyler, "Enumerating Building Block Semantics in Genetic Programming" (2007). Faculty Working Papers. 10.