This definition describes a possibility of exchanging documents and data sets between measurement service companies and property management companies via a web service. Both communication directions are taken into account. The direction heat measurement service to property management is called OUT in the service, The direction from property management to heat measurement service is referred to as IN. The different transmission directions of the documents can be found in the URI. It is irrelevant whether a single message or a special service call originates from the heat measurement service or from the property management. All service calls are defined for property management as calling party and measuring service company as provider of the service. The service is protected with basicAuth authentication and must be transmitted on a secure channel (HTTPS/SSL). Changes in Version 1.1 are http 500/501 codes and dedicated documenttypes Changes in Version 1.2 are extensions to the dedicated documenttypes