In the Input Transformation Policy of the default text delimited driver
the stylesheet creates a source DN (which is in actual fact more like a CN
really) by concatenating the surname and givenname. I want to create a
rule that queries that value and compares it to my datastore but I can't
see how to do it as the value doesn't exist as a real attribute in my
source datastore because it is just a flat text file.

I want to create a rule that says:

If source-dn = dest-cn
then
do action.