  Genetic programming and artificial life systems commonly employ tag-matching
schemes to determine interactions between model components. However, the
implications of criteria used to determine affinity between tags with respect
to constraints on emergent connectivity, canalization of changes to
connectivity under mutation, and evolutionary dynamics have not been
considered. We highlight differences between tag-matching criteria with respect
to geometric constraint and variation generated under mutation. We find that
tag-matching criteria can influence the rate of adaptive evolution and the
quality of evolved solutions. Better understanding of the geometric,
variational, and evolutionary properties of tag-matching criteria will
facilitate more effective incorporation of tag matching into genetic
programming and artificial life systems. By showing that tag-matching criteria
influence connectivity patterns and evolutionary dynamics, our findings also
raise fundamental questions about the properties of tag-matching systems in
nature.
