TaxonomyReader is the read-only interface with which the faceted-search library uses the taxonomy during search time.
Equivalent representations of the taxonomy's parent info, used internally for efficient computation of facet results: "youngest child" and "oldest sibling"
TaxonomyWriter is the interface which the faceted-search library uses to dynamically build the taxonomy at indexing time.
A CategoryPath holds a sequence of string components, specifying the hierarchical name of a category.
Exception indicating that a certain operation could not be performed on a taxonomy related object because of an inconsistency.