The present invention relates to a method of preparing RAFT, ATRP or NMRP functionalized thin film composite polyamide membranes on a microporous substrate. The result set for each media class is then analyzed to assess whether the media item belongs to that class. A manipulated variable is determined from the control deviation, by which manipulated variable the control valve is positioned andor maintained in the position predefined by the reference variable. When the extensible value type is defined, an associated set of functions are developed to operate on the type.