Data Object

Description

A Data Object is a fundamental data structure used in various 3GPP specifications, particularly in smart card (UICC) and device management contexts. It is defined as information coded as TLV (Tag-Length-Value) objects, where each object consists of a Tag that identifies the type of data, a Length that specifies the size of the Value field, and a Value that contains the actual data. This encoding is widely used in protocols such as those based on ASN.1 BER-TLV, and it provides a flexible and extensible way to represent complex data structures.

In the context of 3GPP TS 31.121, which specifies the UICC-terminal interface for the IP Multimedia Services Identity Module (ISIM), Data Objects are used to encode files and commands. For example, the ISIM application contains various Elementary Files (EFs) that store parameters like the Private User Identity, Public User Identity, and Home Network Domain Name. These files are often encoded as TLV objects to allow for easy parsing and future extension. Similarly, in remote management protocols like OMA-DM, Data Objects are used to represent management objects and their properties.

The TLV structure is highly versatile: the Tag can be a single byte or multi-byte, the Length can be encoded in definite or indefinite form, and the Value can contain primitive data or nested TLV objects. This nesting allows for hierarchical data representation, which is essential for complex structures like the ISIM file system or the 5G UE configuration parameters. The Data Object concept is also used in other 3GPP specifications, such as TS 24.301 for NAS protocol messages, where Information Elements (IEs) are often encoded as TLV.

One of the key advantages of Data Objects is their self-describing nature. Since each object includes a Tag and Length, a parser can easily skip unknown or unsupported objects, ensuring forward and backward compatibility. This is particularly important in telecommunications, where networks and devices from different vendors and generations must interoperate. The TLV encoding also allows for efficient storage and transmission, as the Length field enables precise extraction of the Value without relying on delimiters.

Data Objects are not limited to smart cards; they are also used in network management interfaces, such as the Itf-N interface between the Network Manager and Element Manager, where configuration data is exchanged as TLV-encoded objects. The term is defined in 3GPP TR 21.905 and further detailed in TS 31.121, reflecting its broad applicability across 3GPP systems.

Purpose & Motivation

The Data Object concept exists to provide a standardized, flexible, and extensible way to encode structured information in 3GPP systems. It solves the problem of representing complex, hierarchical data in a format that is both machine-readable and human-understandable, while ensuring interoperability across different vendors and generations of equipment. The TLV encoding allows for easy addition of new data elements without breaking existing parsers, which is crucial for long-term evolution of specifications.

Before the widespread adoption of TLV encoding, various proprietary or less flexible formats were used, leading to interoperability issues and difficulty in extending data structures. The standardization of Data Objects in 3GPP specifications, particularly in the smart card domain, ensured that UICC applications from different vendors could be read and managed by any compliant terminal. This was essential for the global roaming of subscribers and the deployment of new services like ISIM for IMS.

The term 'Data Object' was introduced in Rel-4, coinciding with the maturation of 3GPP specifications and the need for a common vocabulary. It has since been carried forward unchanged, demonstrating its fundamental nature and continued relevance. Today, Data Objects are used in a wide range of 3GPP protocols, from UICC file access to network management, and they remain a cornerstone of structured data representation in telecommunications.