>> A C# SOAP client will have trouble consuming a Java WSDL, and so on. I have had no issues getting a C# client on Windows to work with a Java SOAP server run

>> A C# SOAP client will have trouble consuming a Java WSDL, and so on. I have had no issues getting a C# client on Windows to work with a Java SOAP server running on Tomcat using AXIS. I even have an Android client talking to that SOAP server with no issues. >> In theory, no. In practice, interoperability is by no means a given. That's because it's contract driven, with REST any changes on the server in the API will not break the client's compile so you won't know it broken until the customer calls at 2 AM. Unless of course you have 100% unfailing testing processes. >> if you make a breaking API change in any system, you should have a way to do it so clients aren't caught flat-footed when their app breaks. Cool yes right, SOAP. >> REST does allow for custom media types that include versioning. If REST ever gets to that level of specification we will have SOAP.