I assume you've run into the ever-popular case where the subject matter "expert" cannot, as it turns out, actually explain what it is that they do. As part of their jobs. Every. Frakin'. Week. (See also: ISO-9000 documentation. Part of my initial bonding experience with Deb, me just joining her company as a former tech writer back in IT, she as the head of admin who got sucked into the company's ISO-9000 project.)