| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| /** |
| * Taxonomy of Categories. |
| * |
| * <p>Facets are defined using a hierarchy of categories, known as a <i>Taxonomy</i>. For example, |
| * the taxonomy of a book store application might have the following structure: |
| * |
| * <ul> |
| * <li>Author |
| * <ul> |
| * <li>Mark Twain |
| * <li>J. K. Rowling |
| * </ul> |
| * </ul> |
| * |
| * <ul> |
| * <li>Date |
| * <ul> |
| * <li>2010 |
| * </ul> |
| * <ul> |
| * <li>March |
| * <li>April |
| * </ul> |
| * <li>2009 |
| * </ul> |
| * |
| * <p>The <i>Taxonomy</i> translates category-paths into integer identifiers (often termed |
| * <i>ordinals</i>) and vice versa. The category <code>Author/Mark Twain</code> adds two nodes to |
| * the taxonomy: <code>Author</code> and <code>Author/Mark Twain</code>, each is assigned a |
| * different ordinal. The taxonomy maintains the invariant that a node always has an ordinal that is |
| * < all its children. |
| */ |
| package org.apache.lucene.facet.taxonomy; |