The client interface itself differs in format among the types of Open Client:
For a .NET client, it is a .NET assembly.
For a Java client, it is a set of Java classes.
For a Web service client, it is whatever native mechanism on the client platform best represents the client interface definition, which is made available to the client by OpenEdge in the standard Web service manner, using Web Service Definition Language (WSDL) presented in a WSDL file.
For .NET and Java Open Clients, OpenEdge can generate the client interface as well as the definition. For Web service clients, OpenEdge generates the client interface definition, but leaves it to the client platform (as is standard) to generate the client interface itself.