I faced some problems trying to filter a metadata catalog (Geonetwork version 18.104.22.168) through a CSW GetRecords POST-Request using XPaths. My problem is that I'm not sure how to implement XPaths in the request. I tried the following code:
As you can see in the code I simply used the XPath for the <ogc:PropertyName> parameter (as defined in http://portal.opengeospatial.org/files/?artifact_id=20555 Page 154: 10.8.4.11.5 Property references).
The request always leads to 0 results so something has to be wrong with the GetRecords request.
Replacing the XPath with 'Identifier' makes the code work as it should: