2.2. Structure of service-oriented architecture and its application on X-Road
E-state of Estonia has a service-oriented architecture and its major part is X-Road – secure data exchange channel. Services on X-Road are dataservices. Dataservice is a communication method which enables exchanging data between the parties via public internet.
X-Road is distributed and parties are connected directly with P2P model. The core technology of X-Road is status-free, which means that a response is following the request during the same connection. Parties on X-Road are equal and each party can be a provider as well as a user of the dataservice. Availability and structure of X-Road ensures clarity when information is held by one or another party, as the parties are connected directly and data exchange is synchronous.
WSDL descriptions together with dataservice policy (on which bases, to whom and why the service is provided) and quality parameters of dataservice (functionality, reliability and efficiency) are published in the service directory. X-Road includes a distributed service directory, which the X-Road members can use through metaservices by submitting a HTTP GET request to the security server. Metaservices enable X-Road members to download the list of X-Road members and subsystems or potential dataservice providers. Then, it is possible to request a list of specific dataservices and download a WSDL format description of dataservices. Metaservices and their use are described further in module 4.
Superstructure of distributed service directory of X-Road is RIHA (management system of state information system), which includes, in addition to a WSDL format description of dataservices, information about the responsible and authorised processors of information systems and databases, and on which legal bases databases are maintained and data are processed (Figure 11). RIHA provides information about state information systems, data collected therein, and offered dataservices without installing a security server. For example, affiliation of membership is handled as well via RIHA.
Figure 11 Implementation of service-oriented architecture on X-Road