src/plugin/nutch-extensionpoints/plugin.xml

<?xml version="1.0" encoding="UTF-8"?>
<!--
 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
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     http://www.apache.org/licenses/LICENSE-2.0

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 See the License for the specific language governing permissions and
 limitations under the License.
-->
<plugin
   id="nutch-extensionpoints"
   name="the nutch core extension points"
   version="2.0.0"
   provider-name="nutch.org">

   <!-- this file hosts all extension points nutch core code offers. 
   Please not that plugins can define extension points as well to be extendable.-->

<extension-point
      id="org.apache.nutch.exchange.Exchange"
      name="Nutch Exchange"/>

<extension-point
      id="org.apache.nutch.indexer.IndexingFilter"
      name="Nutch Indexing Filter"/>

<extension-point
      id="org.apache.nutch.indexer.IndexWriter"
      name="Nutch Index Writer"/>

<extension-point
      id="org.apache.nutch.parse.Parser"
      name="Nutch Content Parser"/>
 
<extension-point
      id="org.apache.nutch.parse.HtmlParseFilter"
      name="HTML Parse Filter"/>

<extension-point
      id="org.apache.nutch.protocol.Protocol"
      name="Nutch Protocol"/>

<extension-point
      id="org.apache.nutch.net.URLFilter"
      name="Nutch URL Filter"/>

<extension-point
        id="org.apache.nutch.net.URLExemptionFilter"
        name="Nutch URL Ignore Exemption Filter"/>

<extension-point
      id="org.apache.nutch.net.URLNormalizer"
      name="Nutch URL Normalizer"/>

<extension-point
      id="org.apache.nutch.scoring.ScoringFilter"
      name="Nutch Scoring"/>

<extension-point
      id="org.apache.nutch.segment.SegmentMergeFilter"
      name="Nutch Segment Merge Filter"/>

<extension-point
      id="org.apache.nutch.publisher.NutchPublisher"
      name="Nutch Publisher"/>

</plugin>