http://msmvps.com/blogs/manoj/archive/2009/01/16/using-interception-with-dependency-injection-el-4-1-and-unity-spring-1-2-create-new-avenues.aspxIt is customary to conceive any large application to be composed of several logical layers. It is also a practice to reduce the coupling between the layers. Typically, one would create an interface for each class of each layer and they would be coupledenCommunityServer 2008.5 SP2 (Build: 40407.4157)