A method and system for client applications to invoke the services of server applications. A business service system allows a user of a client application to specify the provider of a business service and to specify the communications protocols and transport mechanisms to be used when invoking such business services. The business service system provides a business service proxy that is invoked by client applications when using a business service. The business service proxy uses a mapping of web service to business service to send a request to the server application, which implements the business service in an appropriate format and using an appropriate transport mechanism. The mapping may be customized to point to a different implementation of the business service. The mapping may point to a business service that executes remotely from or locally to the client application.