# Package org.apache.lucene.facet.taxonomy.directory

Taxonomy index implementation using on top of a Directory.

- Interface Summary
  Interface | Description
  --- | ---
  DirectoryTaxonomyWriter.OrdinalMap | Mapping from old ordinal to new ordinals, used when merging indexes with separate taxonomies.

- Class Summary
  Class | Description
  --- | ---
  DirectoryTaxonomyReader | A `TaxonomyReader` which retrieves stored taxonomy information from a `Directory`.
  DirectoryTaxonomyWriter | `TaxonomyWriter` which uses a `Directory` to store the taxonomy information on disk, and keeps an additional in-memory cache of some or all categories.
  DirectoryTaxonomyWriter.DiskOrdinalMap | `DirectoryTaxonomyWriter.OrdinalMap` maintained on file system
  DirectoryTaxonomyWriter.MemoryOrdinalMap | `DirectoryTaxonomyWriter.OrdinalMap` maintained in memory
  ReindexingEnrichedDirectoryTaxonomyWriter | Use this `TaxonomyWriter` to append arbitrary fields to the ordinal documents in the taxonomy.