The service gets an unknown object containing a list of three values [column, operator, value] For example, EMAIL - like - \"TEST\"
Based on the resulting list to
There are two key parts to this answer. One is the "dynamic" element, and the other are the $$ literal elements around the "operator" in your question.
select * from YOURTABLE email $operator$ #testvalue#
See also the DataMapper Dynamic SQL documentation on this topic.