Thank you for your reply. I have read the SOS developer guide and I noticed there is a section named “New Observation types”. In the SOS requests, we denote observation type by an URL, such as http://www.opengis.net/def/observationType/OGC- OM/2.0/OM_CategoryObservation. There are 16 bulit-in observation types implemented in the 52north SOS. So the question is that how I can map the url in the SOS request to the observation type defined in Java classes?