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 * 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.
 */
/**
 * Defines the {@link org.apache.beam.sdk.transforms.windowing.Window} transform for dividing the
 * elements in a PCollection into windows, and the {@link
 * org.apache.beam.sdk.transforms.windowing.Trigger} for controlling when those elements are output.
 *
 * <p>{@code Window} logically divides up or groups the elements of a {@link
 * org.apache.beam.sdk.values.PCollection} into finite windows according to a {@link
 * org.apache.beam.sdk.transforms.windowing.WindowFn}. The output of {@code Window} contains the
 * same elements as input, but they have been logically assigned to windows. The next {@link
 * org.apache.beam.sdk.transforms.GroupByKey}s, including one within composite transforms, will
 * group by the combination of keys and windows.
 *
 * <p>Windowing a {@code PCollection} allows chunks of it to be processed individually, before the
 * entire {@code PCollection} is available. This is especially important for {@code PCollection}s
 * with unbounded size, since the full {@code PCollection} is never available at once.
 *
 * <p>For {@code PCollection}s with a bounded size, by default, all data is implicitly in a single
 * window, and this replicates conventional batch mode. However, windowing can still be a convenient
 * way to express time-sliced algorithms over bounded {@code PCollection}s.
 *
 * <p>As elements are assigned to a window, they are placed into a pane. When the trigger fires all
 * of the elements in the current pane are output.
 *
 * <p>The {@link org.apache.beam.sdk.transforms.windowing.DefaultTrigger} will output a window when
 * the system watermark passes the end of the window. See {@link
 * org.apache.beam.sdk.transforms.windowing.AfterWatermark} for details on the watermark.
 */
package org.apache.beam.sdk.transforms.windowing;
