Is there a minimum technical requirement of systems to be able to connect X-Road? How do dated legacy systems connect?

X-Road provides REST and SOAP interfaces that information systems can use to connect X-Road. Existing REST based systems can be connected using the REST interface without any additional changes, e.g. an existing REST service can be published in X-Road in a minute. Existing SOAP based systems can be connected using the SOAP interface, but it requires some changes to the information system (or an additional adapter component) since X-Road’s SOAP interface has some X-Road specific requirements.