I would like to thank the HACK for some useful suggestions regarding BMW service. If I understood his comments correctly, he implied that understanding the job demands of a service writer would be useful. I wanted to have the wiper blades replaced - they are over a year old. I originally asked to have them replaced but then realized that "replacing a part at customer request" wouldn't be successful. The service writer then confirmed that the blades chattered and smeared. Hence, a defective part is perhaps the easiest documentation for warranty service. Although this may seem trivial, I think that it is a very useful approach. I apologize to the HACK if I misunderstood his note.