The guidelines discuss the service layer with its service interfaces and data/message/fault contracts. They also discuss the business layer with its logic/workflow components and entities as well as the 'optional' application facade. What is unclear still to me after studying this guide is where the implementations of the service interfaces belong. Does the application facade in the business layer implement these interfaces, or does a separate 'service facade' exist to make calls to the business layer and it's facade/raw components? (With the former, there would be less seemingly trivial calls to yet another layer, though with the latter I could see how the service layer could remove the concerns of translating business entities to data contracts from the business layer.)