/*
 * 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.xerces.impl;

import java.io.IOException;

import org.apache.xerces.xni.XNIException;
import org.apache.xerces.xni.grammars.XMLDTDDescription;
import org.apache.xerces.xni.parser.XMLEntityResolver;
import org.apache.xerces.xni.parser.XMLInputSource;

/**
 * <p>This interface extends <code>XMLEntityResolver</code> providing
 * a method to resolve external subsets for documents which do not 
 * explicitly provide one. The application can register an object that 
 * implements this interface with the parser configuration. If registered, 
 * it will be queried to locate an external subset when none is provided, 
 * even for documents that do not contain DOCTYPE declarations. If the 
 * registered external subset resolver does not provide an external subset
 * for a given document, it should return <code>null</code>.</p>
 *
 * @xerces.internal
 * 
 * @author Michael Glavassevich, IBM
 *
 * @version $Id: ExternalSubsetResolver.java 446761 2006-09-15 21:59:29Z mrglavas $
 */
public interface ExternalSubsetResolver 
    extends XMLEntityResolver {
	
    //
    // ExternalSubsetResolver methods
    //

    /**
     * <p>Locates an external subset for documents which do not explicitly
     * provide one. If no external subset is provided, this method should
     * return <code>null</code>.</p>
     *
     * @param grammarDescription a description of the DTD
     *
     * @throws XNIException Thrown on general error.
     * @throws IOException  Thrown if resolved entity stream cannot be
     *                      opened or some other i/o error occurs.
     */
    public XMLInputSource getExternalSubset(XMLDTDDescription grammarDescription)
        throws XNIException, IOException;

} // interface ExternalSubsetResolver
