[GeoNetwork-users] Details of Metadata Search Mechanism/Algorithm?

We would like to instruct our users about loading
metadata fields with values to work with the various
search options. We would like to know how the user
input is translated into search criteria for specific
metadata records that match the inputs. In particular,
what metadata fields are examined for matches?
Does anyone know where this is documented, or what
parts of the source code would show this?
How does the Category selection refer to the metadata
record, specifically, if I want a metadata record to
be returned from a search on category C, where in the
metadata record do I put the "C:"?
thanks!!
David Briggs
briggs@anonymised.com