http://lucene.apache.org/lucene-parent/lucene-queryparser: Lucene QueryParsers module (The Apache Software Foundation) 
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 * 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
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 *     http://www.apache.org/licenses/LICENSE-2.0
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package org.apache.lucene.queryparser.surround.query;
import java.io.IOException;


Interface for queries that can be nested as subqueries
into a span near.

/**
 * Interface for queries that can be nested as subqueries
 * into a span near.
 */
public interface DistanceSubQuery {
  
When distanceSubQueryNotAllowed() returns non null, the reason why the subquery
is not allowed as a distance subquery is returned.

When distanceSubQueryNotAllowed() returns null addSpanNearQueries() can be used
in the creation of the span near clause for the subquery.

/** When distanceSubQueryNotAllowed() returns non null, the reason why the subquery
   * is not allowed as a distance subquery is returned.
   * <br>When distanceSubQueryNotAllowed() returns null addSpanNearQueries() can be used
   * in the creation of the span near clause for the subquery.
   */
  String distanceSubQueryNotAllowed();
    
  void addSpanQueries(SpanNearClauseFactory sncf) throws IOException;
}