Joined: 28 September 2007
If I have interpretated your question correctly an electrical harness is a preformed set of cables with terminations used in the assembly of electrical apparatus and machines.
The classic place for them is within a car. Lift the bonnet of a car and inside you will find a wiring harness usually covered in a a tape. The harness works its way around the engine bay with individual wires coming out of it to connectors that plug onto the various sensors and car components. They are however used in various other aspects of the manufacturing industry. You ar ealso starting to find them in prefabricated and sectionalised buildings now.
The roles and responsibilities would be defined by the company who the design engineer works for but they will consist of selection of appropriate cable sizes, insulation, connectors, layout of the harness, covering materials etc.