package org.apache.lucene.search;

/**
 * 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.
 */

import java.io.IOException;

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.util.DocIdBitSet;

/** 
 *  Abstract base class providing a mechanism to use a subset of an index
 *  for restriction or permission of index search results.
 *  <p>
 */
public abstract class Filter implements java.io.Serializable {
  
  /**
   * Creates a {@link DocIdSet} that provides the documents which should be
   * permitted or prohibited in search results. <b>NOTE:</b> null can be
   * returned if no documents will be accepted by this Filter.
   * <p>
   * Note: This method might be called more than once during a search if the
   * index has more than one segment. In such a case the {@link DocIdSet}
   * must be relative to the document base of the given reader. Yet, the
   * segment readers are passed in increasing document base order.
   * 
   * @param reader a {@link IndexReader} instance opened on the index currently
   *         searched on. Note, it is likely that the provided reader does not
   *         represent the whole underlying index i.e. if the index has more than
   *         one segment the given reader only represents a single segment.
   *          
   * @return a DocIdSet that provides the documents which should be permitted or
   *         prohibited in search results. <b>NOTE:</b> null can be returned if
   *         no documents will be accepted by this Filter.
   * 
   * @see DocIdBitSet
   */
  public abstract DocIdSet getDocIdSet(IndexReader reader) throws IOException;
}

@@ -982,124 +982,77 @@
 ass 
-providing a mechanism to use a subset of an index%0A *  for restriction or permission of index search results.%0A *  %3Cp%3E
+for restricting which documents may%0A *  be returned during searching.
 %0A */
@@ -1156,29 +1156,27 @@
 cIdSet%7D 
-that provides
+enumerating
  the doc
@@ -1174,37 +1174,36 @@
 g the documents 
-which
+that
  should be%0A   * 
@@ -1216,22 +1216,8 @@
 ted 
-or prohibited 
 in s
@@ -1278,38 +1278,34 @@
 if no documents 
-will b
+ar
 e accepted by th
@@ -1351,13 +1351,12 @@
 hod 
-might
+will
  be 
@@ -1366,255 +1366,172 @@
 led 
-more than once during a search if the
+once per segment in
 %0A   *
+ the
  index 
-has more than one segment. In such a case the %7B@link DocIdSet%7D%0A   * must be relative to the document base of the given reader. Yet, the%0A   * segment readers are passed in increasing document base or
+during searching.  The returned %7B@link DocIdSet%7D%0A   * must refer to document IDs for that segment, not for%0A   * the top-level rea
 der.

tweak javadocs