Instead of abstracting individual, static Service interfaces, Business Services must abstract sets of such interfaces via content-based routing and transformation operations on an intermediary like an ESB. Implement those abstraction operations as a matter of policy, and you shift control of the behavior of your SOA deployment to the metadata-driven policy layer. Get all this right and you have enormous control and flexibility over your legacy environment. The problem is, of course, that it’s extraordinarily difficult to get all these moving parts right.