[GeoNetwork-users] Adding new queries within Geonetwork

Hi I'm Nicola Burgarella, I have a problem doing my thesis,I have to to edit the mask of GeoNetwork and add other forms that query the database in addition to existing ones, but I have not to create a jsp application that uses a postgresql (for relational and linguistic queries with xpath function and tsvector datatype), but modifying the existing software.I don't know how to do it and honestly i did not find enough information about it. For this reason I decided installing both jar and source version(with ant, maven here http://tinyurl.com/alxloyu ).
The initial page of GeoNetwork refers to the file config-gui.xml,but looking at the source code of Geonetwork I realized that GeoNetwork uses both Spring MVC,hibernate and web services.(Thus I studied hibernate,spring mvc and axis2 hoping to figure out what's the model that handles that xml to the home page of GeoNetwork unfortunately without success).
Could you point me some indications in how to proceed ?every suggestions are really appreciated.Thank you
Nicola