To understand the gnowsis retrieval service, checkout the project from here:

 * https://gnowsis.opendfki.de/repos/gnowsis/trunk/gnowsis_retrieval/

and then read the documentation:

 * https://gnowsis.opendfki.de/repos/gnowsis/trunk/gnowsis_retrieval/doc/help.html

Debugging:
 look at this local page:

our own design:

http://www.dfki.uni-kl.de/~heim/index_search.html

xml example:

http://gnowsis.opendfki.de/repos/gnowsis/trunk/gnowsis/src/org/gnowsis/search/retrieval/test/

http://www.xml.com/pub/a/2002/06/26/q-a.html

http://www.xml.com/pub/a/2001/02/07/trxml9.html

xslt:

http://web.oreilly.com/news/xslt_0801.html

http://forum.java.sun.com/thread.jspa?threadID=492023&messageID=2314031

http://www.developer.com/java/other/article.php/629071

http://www.w3schools.com/xsl/

http://freilauf.gnowsis.com/2005/uniklsemweb/project-browser/imgdesc.xsl

http://freilauf.gnowsis.com/2005/uniklsemweb/index.html

http://www.dfki.uni-kl.de/~schwarz/Spiel2003/Spiel2003.html

http://rdfweb.org/people/damian/treehugger/introduction.html

xalan:

http://xml.apache.org/xalan-j/samples.html

http://xml.apache.org/xalan-j/apidocs/index.html

treehugger:

http://rdfweb.org/people/damian/treehugger/

twig:

http://www.xml.com/pub/a/2001/03/21/xmltwig.html