Given a list of parameters (e.g. abstract, dateFrom, sortBy, themeKey), this service performs a search and returns limited information on each result (xml.metadata.get will probably need to be used to get any user-friendly information for a result). A list of fields can be found here. Additional fields can also be added by editing some of GeoNetwork's XSLT code. A walk-through of this is beyond the scope of this documentation, but /geonetwork/web/geonetwork/xml/search/lucene.xsl and /geonetwork/web/geonetwork/xml/schemas/iso19139/index-fields.xsl (or the same file in another one of the schema directories) are the files that should be modified, and the modification should usually be fairly straightforward given the examples of how other fields are established in those files.