In Which a Concept Model Makes Me Giddy
http://www.uie.com/articles/concept_models/

Brown, Dan
User Interface Engineering
2009

Abstract:

Concept models aren't for everyone. When I show fellow designers these artifacts, I sometimes get "You show that to clients?" Like any deliverable, there's a time and a place for concept models. If you're anything like me, however, you think visually. Even if your models don't see the light of day, a good model can help you get a better grip on the problem, or lay some groundwork for your designs.