3GPP TR 22.985
Service requirement for the UDC  describes the architecture of the User Data Convergence, a concept that proposes to move the user data from where it has been distributed and siloed in Network Elements, Applications, and other network resources to a single logical consolidated facility here called User Data Repository (UDR) where it can be accessed, stored and managed in a common way.
The introduction of a User Data Convergence of user data for network services and management applications could significantly enhance the ability of 3GPP based networks to offer complex and combined services. User data can be decomposed and reformed by a common data model framework (e.g. tree-like data model, rational data model) provided by UDR. In that case, user data categorized by services can be regrouped and identified by user ID, leaving no data redundancy. Also, convergence in data model will unify the user data access interface and its protocol, which will promote new service application development. Thereby, the capability of user data convergence can be open to creation of data-less applications.
Methods for data protection against access by unauthorized parties are outside the scope of this document.
3GPP TS 32.181
UDC Framework for Model Handling and Management  and TS 29.335
UDC; User Data Repository Access Protocol over the Ud interface; Stage 3  provide various types of information and data models associated with the architecture of UDC.
These include the Common Baseline Information Model (CBIM) (see TS 32.182
), the Specialized Information Model (SpIM), Application Information Models (AIMs), Application Data Models (ADMs), and the Consolidated Data Model (CDM) of the User Data Repository (UDR).
Figure 1 from TS 32.181
UDC Framework for Model Handling and Management  shows the operational environment of the UDC.
In addition to the models previously mentioned, Figure 1.1 introduces the aspect of the Provisioning Gateway, which is essential for the operation of the UDR. The Provisioning Gateway provides a single logical point for access to provisioning of user data for all services in the UDR. The Provisioning Gateway is shown supporting an interaction with the operator's BSS; by implication this interaction is associated with the provisioning of user subscription and service data in the UDR via the Provisioning Gateway.
This study analyzes the progression of information models displayed in the above figure using some specific application examples, in particular the applications of HSS-IMS and MMTel. It provides guidelines and preliminary requirements for the BSS provisioning capabilities and information model handling when new applications and related services are implemented in the operator's UDR by doing the following:
Develop several example initial SpIMs for discussion purposes.
Examine what BSS interactions with the Provisioning Gateway would be required to support provisioning of user service and subscription data in the UDR for these SpIMs.
Study the relationship to the information model of TS 32.172 Subscription Management (SuM) Network Resource Model (NRM) IRP Information Service .
Develop understanding of CBIM-derived entities of Application Information Models (AIM) for HSS-IMS and MMTel from application data elements available in TS 29.364 IMS Application Server service data descriptions for AS interoperability , TS 23.008 Organization of subscriber data , and other relevant specifications.
Discuss the integration and consolidation of these AIM entities with the example initial SpIMs above.
Evaluate the potential changes to the BSS provisioning interactions for the implementation of HSS-IMS and MMTel applications in the UDR and implications concerning the information model of TS 32.172 Subscription Management (SuM) Network Resource Model (NRM) IRP Information Service .
This study does not derive findings concerning the Ud reference point, the subject of TR 23.845
Study on UDC Evolution .