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

Taxonomy of Categories

See:
Description

Interface Summary
TaxonomyWriter: TaxonomyWriter is the interface which the faceted-search library uses to dynamically build the taxonomy at indexing time.

Class Summary
CategoryPath: Holds a sequence of string components, specifying the hierarchical name of a category.

ParallelTaxonomyArrays

Returns 3 arrays for traversing the taxonomy: `parents`: `parents[i]` denotes the parent of category ordinal `i`. `children`: `children[i]` denotes a child of category ordinal `i`. `siblings`: `siblings[i]` denotes the sibling of category ordinal `i`. To traverse the taxonomy tree, you typically start with `children[0]` (ordinal 0 is reserved for ROOT), and then depends if you want to do DFS or BFS, you call `children[children[0]]` or `siblings[children[0]]` and so forth, respectively.

TaxonomyReader: TaxonomyReader is the read-only interface with which the faceted-search library uses the taxonomy during search time.
TaxonomyReader.ChildrenIterator: An iterator over a category's children.

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

# Taxonomy of Categories

Facets are defined using a hierarchy of categories, known as a Taxonomy.
For example, in a book store application, a Taxonomy could have the following hierarchy:

- Author

- Mark Twain
- J. K. Rowling

- Date

- 2010
- 2009

The Taxonomy translates category-paths into category-ordinal and vice versa.

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