Service Contracts in Indigo

Don Box made it clear.

Indigo allows service contracts to be expressed either in an XML format (specifically WSDL/1.1) or as annotated CLR interfaces. In reality, neither of these formats is the "native" contract format.

The initiator (commonly called the "client") and the service (commonly called the "server") by definition have distinct definitions of the contract used to communicate.

Read, read again, and think about it.