OntologyPlugin

[This text comes straight from the README.TXT written by John Xing]

Ontology plugin is a contribution from Michael J Pan. Currently it is used to do one kind of query refinement as implemented in refine-query-init.jsp and refine-query.jsp (both are called by search.jsp).

By default, ontology plugin is compiled, but query refinement based on it is ignored in search.jsp. To enable query refinement, do the following:

1. specify url(s) of owl files to property extension.ontology.urls in ./conf/nutch-default.xml (or better, ./conf/nutch-site.xml).
2. uncomment refine-query-init.jsp and refine-query.jsp in search.jsp

If you want to check ontology defined by different owl file, modify property extension.ontology.urls in ./conf/nutch-default.xml (or better, ./conf/nutch-site.xml), and insert the following to ./bin/nutch:

elif [ "$COMMAND" = "ontology" ] ; then
  for f in $NUTCH_HOME/build/plugins/ontology/*.jar; do
    CLASSPATH=${CLASSPATH}:$f;
  done
  CLASS='org.apache.nutch.ontology.OntologyImpl'

Possible issue:

If search.jsp fails with this or similar error:

root cause

java.lang.NoSuchFieldError: actualValueType
        at
com.hp.hpl.jena.datatypes.xsd.XSDDatatype.convertValidatedDataValue(XSDDatatype.java:371)

It is because jena and tomcat are using conflicting versions of the same xerces library. To solve this, one needs to update tomcat's xerces library. Here's a reference:

http://jena.sourceforge.net/jena-faq.html#general-1

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