content: /* Copyright 2010, Object Management Group, Inc.
   * Copyright 2010, PrismTech, Inc.
   * Copyright 2010, Real-Time Innovations, Inc.
   * All rights reserved.
   *
   * Licensed 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.
   */
  
  package org.omg.dds.core.policy;
  
  import java.util.concurrent.TimeUnit;
  
  import org.omg.dds.core.Duration;
  
  
  /**
   * Specifies the maximum duration of validity of the data written by the
   * {@link org.omg.dds.pub.DataWriter}. The default value of the lifespan duration is infinite.
   *<p>
   * <b>Concerns:</b> {@link org.omg.dds.topic.Topic}, {@link org.omg.dds.pub.DataWriter}
   *<p>
   * <b>RxO:</b> N/A
   *<p>
   * <b>Changeable:</b> Yes
   *<p>
   * The purpose of this QoS is to avoid delivering "stale" data to the
   * application.
   * <p>
   * Each data sample written by the DataWriter has an associated "expiration
   * time" beyond which the data should not be delivered to any application.
   * Once the sample expires, the data will be removed from the DataReader
   * caches as well as from the transient and persistent information caches.
   * <p>
   * The "expiration time" of each sample is computed by adding the duration
   * specified by the LIFESPAN QoS to the source time stamp. As described in
   * {@link org.omg.dds.pub.DataWriter#write(Object)} and
   * {@link org.omg.dds.pub.DataWriter#write(Object, org.omg.dds.core.Time)}, the source time
   * stamp is either automatically computed by the Service each time the
   * write operation is called, or else supplied by the application.
   * <p>
   * This QoS relies on the sender and receiving applications having their
   * clocks sufficiently synchronized. If this is not the case and the Service
   * can detect it, the DataReader is allowed to use the reception time stamp
   * instead of the source time stamp in its computation of the "expiration
   * time."
   */
  public interface Lifespan
  extends QosPolicy.ForTopic, QosPolicy.ForDataWriter
  {
      public Duration getDuration();
  
  
      // --- Modification: -----------------------------------------------------
  
      /**
       * Copy this policy and override the value of the property.
       * @param duration               Specifies a duration for the length in time of the validity of the data.
       *
       * @return  a new Lifespan policy
       */
      public Lifespan withDuration(Duration duration);
  
      /**
       * Copy this policy and override the value of the property.
       * @param duration               Specifies a long duration for the length in time of the validity of the data.
       * @param unit                   The TimeUnit which the duration describes (i.e. TimeUnit.SECONDS or TimeUnit.MILLISECONDS)
       *
       * @return  a new Lifespan policy
       */
      public Lifespan withDuration(long duration, TimeUnit unit);
  }
  