## 3 Description of Railway Identity Management Service
The resource is represented by the userList data structure, which is a structure containing information about all users and a self-referring URL. The userID resource refers to information about an individual user who is registered on a UE. The information is represented by a userInfo data structure that comprises information about user presence (context) status and a self-referring URL. The allowed HTTP methods are GET, which retrieves user information, and DELETE, which is used to unregister an individual user. The userFIDs resource represents a list of all of the registered functional identities of a user. The HTTP GET method retrieves all of the registered user functional identities, and the HTTP POST method is used to register a new user functional identity. The resource is represented by the userFIDList data structure, which comprises a collection of user functional identity information (userFIDinfo) and a self-referring URL. The userFID resource refers to information about an individually registered functional identity of a user. The information is represented by userFIDinfo, which comprises the functional identity information and a self-referring URL. The allowed HTTP methods are GET, which retrieves user functional identity information, and DELETE, which is used to unregister an individual user functional identity. The useSubscriptions resource represents all the subscriptions for notifications regarding the registration status of registered UEs. An application uses an HTTP GET method to retrieve a list of all the subscriptions and an HTTP POST method to create a new subscription. The useSubscriptionInfo data type represents subscription data, and it includes: a correlator that is used by an application that tags the resource during a request to create a subscription; the address at which the application wants to receive notifications; the useEventCriteria data type, which is a list of event values to generate notifications about the registration status of UEs: the subscription duration; and the self-referring URL. The useNotification data type represents UE notifications, and it contains the UE address, the UE status related event type (registered, unregistered), timestamp, and a link to other resources related to this notification. The useSubscriptionID resource refers to an individual subscription and the allowed HTTP methods that may be used by an application are: GET, which retrieves information about an existing subscription; PUT, which updates an existing subscription; and DELETE, which terminates a subscription. Figure 6: Flow for registering new UE, retrieving information about the UE, and deregistering the UE. The ueFNSubscriptions resource, userSubscriptions resource, and userFIDSubscriptions resources represent all the subscriptions for notifications about registered UE functional numbers, users, and user functional identities, respectively. A GET method retrieves a list of the respective subscriptions, and a POST method creates a new subscription. The ueFNSubscriptionID, userSubscriptionID, and userFIDSubscriptionID resources represent existing subscriptions for notifications about registered UE functional numbers, users, and user functional identities, respectively. An existing subscription is modified using an HTTP PUT method, it is terminated using an HTTP DELETE method, and read using an HTTP GET method. When a UE is switched off, all the registered identities assigned to it are deregistered. The FRMCS system can also deregister any of the registered identities, and this event is reported to all applications with active subscriptions for notifications about changes in the identity registration status. Figure 7 shows a scenario for controlling subscriptions to notifications about the registration status changes in UE functional numbers. To start a subscription, an application creates a new resource under http://\(\backslash\)apiRoot\(\backslash\)/rim/v1/ueSubscriptions/\(\backslash\){ueSubscriptionID\(\backslash\)}/ueFNSubscriptions.