001    /*
002     * Copyright 2005 Stephen J. McConnell
003     *
004     * Licensed  under the  Apache License,  Version 2.0  (the "License");
005     * you may not use  this file  except in  compliance with the License.
006     * You may obtain a copy of the License at
007     *
008     *   http://www.apache.org/licenses/LICENSE-2.0
009     *
010     * Unless required by applicable law or agreed to in writing, software
011     * distributed  under the  License is distributed on an "AS IS" BASIS,
012     * WITHOUT  WARRANTIES OR CONDITIONS  OF ANY KIND, either  express  or
013     * implied.
014     *
015     * See the License for the specific language governing permissions and
016     * limitations under the License.
017     */
018    
019    package net.dpml.library;
020    
021    /**
022     * Interface implemented by content filters.
023     *
024     * @author <a href="http://www.dpml.net">The Digital Product Meta Library</a>
025     * @version 1.0.0
026     */
027    public interface Filter
028    {
029       /**
030        * Return the filter token.
031        * @return the token
032        */
033        String getToken();
034        
035       /**
036        * Return the filter value.
037        * @param resource the enclosing resource
038        * @return the value
039        * @exception ResourceNotFoundException if the feature referneces an invalid reference
040        */
041        String getValue( Resource resource ) throws ResourceNotFoundException;
042    }