As noted in Section II of Chapter 1, we are considering an architecture that decomposes a complex conglomerate into simpler interactive subdomains. Subdomains (SD) can be treated in a variety of ways ranging from purely numerical methods, such as finite element or finite difference methods, to analytic approaches based on constructible problem–matched Green’s functions (GF) [1–3]. A model SD Green’s function that is well–matched to the actual SD problem configuration can serve as an efficient background kernel in the integral equation formulation for the actual SD–GF.