I resolved this tricky problem. Jena and XWiki both use Xerces. I found the actualValueType field in the xerces API (http://xerces.apache.org/xerces2-j/javadocs/xerces2/org/apache/xerces/impl/… <http://xerces.apache.org/xerces2-j/javadocs/xerces2/org/apache/xerces/impl/dv/ValidatedInfo.html#actualValue>). . The fact is that it seems that XWiki uses a jar file which is less complete than the one provided by Jena (called xercesImpl.jar). I therefore deleted <http://svn.forge.objectweb.org/cgi-bin/viewcvs.cgi/xwiki/xwiki/trunk/lib/xerces-2.4.0.jar?view=log&rev=468>xerces-2.4.0.jar from WEB-INF/lib and replaced it with the one provided by xerces. However, this looks more like a hack to a real solution. Does anyone know where I could configure XWiki to give priority to the Jena jar when I call my plugin rather than to the XWiki one? Thanks a lot! On 05/04/06, *Julien Bourdon* &lt;bourdux(a)gmail.com <mailto:bourdux@gmail.com>> wrote: Hi all! I'm trying to develop a plugin to interact with Jena (http://jena.sourceforge.net <http://jena.sourceforge.net>), a semantic web framework. I developed the plugin as I documented it in the plugin development tutorial. I have a hello() method which works perfectly. however when I try to call this method: public List<String> test1(){ Vector<String> uris = new Vector<String>(); OntModel model = ModelFactory.createOntologyModel(OntModelSpec.RDFS_MEM_RDFS_INF, null ); model.read("http://www.dcs.shef.ac.uk/~zzc05jb/environmentOntology/pollutionInventory.rdfs <http://www.dcs.shef.ac.uk/%7Ezzc05jb/environmentOntology/pollutionInventory.rdfs>"); model.read(" http://www.dcs.shef.ac.uk/~zzc05jb/environmentOntology/instances/disposalRe… <http://www.dcs.shef.ac.uk/%7Ezzc05jb/environmentOntology/instances/disposalRecoveryMethods.rdf>"); Iterator iter = model.listIndividuals(); while(iter.hasNext()){ OntResource ontClass = (OntResource)iter.next(); uris.add(ontClass.getURI()); } return uris; } I get this exception: Error number 4001 in 4: Error while parsing velocity page Tests.OntologyPlugin Wrapped Exception: Invocation of method 'test1' in class secoia.plugin.OntologyPluginApi threw exception class java.lang.NoSuchFieldError : actualValueType I can't really make sense of it. This method works if i use it form a classic Java application. I copied all the Jena jar files to the webapps/xwiki/WEB-INF/lib directory. Moreover, I don't know where this actualValueType comes from. Does it come from XWiki? Any clue on this problem? Thanks a lot! -- _ _ Julien Bourdon (o)(o)--. http://purl.org/net/JulienBourdon \../ ( ) self isAddictedTo:(#Squeak&#linux) m\/m--m'`--. ^true -- _ _ Julien Bourdon (o)(o)--. http://purl.org/net/JulienBourdon \../ ( ) self isAddictedTo:(#Squeak&#linux) m\/m--m'`--. ^true ------------------------------------------------------------------------ -- You receive this message as a subscriber of the xwiki-users(a)objectweb.org mailing list. To unsubscribe: mailto:xwiki-users-unsubscribe@objectweb.org For general help: mailto:sympa@objectweb.org?subject=help ObjectWeb mailing lists service home page: http://www.objectweb.org/wws