Methods and apparatus, including computer program products, for configuration of web services. In general, data is received characterizing web service calls for an application, a placeholder destination for the web service calls, and an identification of a system to be mapped to the placeholder; and a configuration is generated for the web service calls, where the configuration maps the placeholder destination to the system. The configuration may be a configuration of proxy objects to make the web service calls. Mapping the placeholder destination to the system may include generating a configuration including the system in lieu of the placeholder destination. Systems may be included in domains, where a security policy may be applied to systems in a domain.