content: /*
   * 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.
   */
  package org.apache.beam.sdk.transforms;
  
  import org.apache.beam.sdk.PipelineRunner;
  import org.apache.beam.sdk.annotations.Internal;
  
  /**
   * <b><i>For internal use only; no backwards-compatibility guarantees.</i></b>
   *
   * <p>How a view should be physically materialized by a {@link PipelineRunner}.
   *
   * <p>A {@link PipelineRunner} will support some set of materializations, and will reject {@link
   * ViewFn ViewFns} that require materializations it does not support. See {@link Materializations}
   * for known implementations.
   */
  @Internal
  public interface Materialization<T> {
    /**
     * Gets the URN describing this {@link Materialization}. This is a stable, SDK-independent URN
     * understood by a {@link PipelineRunner}.
     */
    String getUrn();
  }
  