## 4 Modeling the Identity Registration Status
The UE's attempt to register an additional functional number fails: for \(\forall\) (\(\mathrm{s_{5}}^{\mathrm{a}}\) \(\mathrm{i_{6}}^{\mathrm{a}}\) \(\mathrm{s_{4}}^{\mathrm{a}}\)) \(\wedge\) (\(\mathrm{s_{4}}^{\mathrm{a}}\) \(\mathrm{i_{9}}^{\mathrm{a}}\) \(\mathrm{s_{5}}^{\mathrm{a}}\)) \(\exists\) (\(\mathrm{s_{3}}^{\mathrm{s}}\) \(\mathrm{i_{3}}^{\mathrm{s}}\) \(\mathrm{s_{3}}^{\mathrm{s}}\)). The user is logged in to the FRMCS system successfully, and the application subscribes for user registration events: for \(\forall\) (\(\mathrm{s_{5}}^{\mathrm{a}}\) \(\mathrm{i_{12}}^{\mathrm{a}}\) \(\mathrm{s_{6}}^{\mathrm{a}}\)) \(\wedge\) (\(\mathrm{s_{6}}^{\mathrm{a}}\) \(\mathrm{i_{13}}^{\mathrm{a}}\) \(\mathrm{s_{7}}^{\mathrm{a}}\)) \(\exists\) (\(\mathrm{s_{3}}^{\mathrm{s}}\) \(\mathrm{i_{5}}^{\mathrm{s}}\) \(\mathrm{s_{4}}^{\mathrm{s}}\)). The user login to the FRMCS system fails: for \(\forall\) (\(\mathrm{s_{5}}^{\mathrm{a}}\) \(\mathrm{i_{12}}^{\mathrm{a}}\) \(\mathrm{s_{6}}^{\mathrm{a}}\)) \(\wedge\) (\(\mathrm{s_{6}}^{\mathrm{a}}\) \(\mathrm{i_{4}}^{\mathrm{a}}\) \(\mathrm{s_{5}}^{\mathrm{a}}\)) \(\exists\) (\(\mathrm{s_{5}}^{\mathrm{s}}\) \(\mathrm{i_{5}}^{\mathrm{s}}\) \(\mathrm{s_{5}}^{\mathrm{s}}\)). The registration of the first user functional identity is successful, and the application subscribes for user functional identity registration events: for \(\forall\) (\(\mathrm{s_{7}}^{\mathrm{a}}\) \(\mathrm{i_{7}}^{\mathrm{a}}\) \(\mathrm{s_{9}}^{\mathrm{a}}\)) \(\wedge\) (\(\mathrm{s_{8}}^{\mathrm{a}}\) \(\mathrm{i_{8}}^{\mathrm{a}}\) \(\mathrm{s_{9}}^{\mathrm{a}}\) \(\mathrm{i_{21}}^{\mathrm{a}}\) \(\mathrm{s_{9}}^{\mathrm{a}}\)) \(\wedge\) (\(\mathrm{sregister (CR) where all UEs, their functional identities, user identities, and user functional identities, which are administered by a railway operator, are enlisted statically. For each identity, the CR has to store the identity's serving profile, which describes the authorizations that each identity has and which groups with special privileges that it belongs to. For each identity, the CR also needs to store the identity of the FRMCS system in which the UE and user are registered. Because there are expected to be a great deal of \"Sensor\"-type UE installed at trackside and on the trains, as well as other types of UE, due to the number of trains and controllers, drivers, train staff members, trackside staff members, other railway staff members, and members of the shunting teams, it is not expected that the information of all of the registered identities will be stored in one FRMCS system. If all of the registered identities are stored in one FRMCS system, then the signaling load to this FRMCS system would be too large. To reduce the signaling load, it is likely that several FRMCS systems will be distributed throughout the railway operator network. In such an arrangement, each FRMCS system is responsible for managing the identities that are registered in its serving area. When UE is switched on, it registers itself in the FRMCS system that it visits (visited FRMCS system). If registration is successful, then the visited FRMCS system stores the registered identities. Once registered, it is not expected that the UE or users will have to register again. As such, the registered identities (and their serving profiles) related to moving trains and users have to be transferred to the new (target) FRMCS system and deleted from the old one. The CR also needs to support information about all of the FRMCS systems in the operator's railway network. The functionality of the location management of registered identities may be implemented as another RESTful service called an Identity Location Management (ILM) service. The ILM service enables the service consumer to do the following:The FRMCSsystems resource is a container for all of the FRMCS systems defined in the operator's railway network. An HTTP GET method retrieves a list of all of the FRMCS systems. The FRMCSsystemID resource represents individual FRMCS system information, including its identity and serving area.