I took Ian's mock exam. He's comparing and comtrasting two-tier and three-tier systems. One of the IBM ICE tests hits on this topic too. I would like to find a authorative source on two-tier vs. three-tier. Larman, in Applying UML and Patterns, cites a published note ( R-401-134 ) by the Gartner Group, Three-Tier Computing Architectures and Beyond. ( Larman's book is wonderful btw ) But I can't find this source. Does anybody know how to find this report or another on 2 vs. 3?