This International Standard establishes a common framework to achieve unambiguous identification in
ITS/RTTT: AVI/AEI applications.
This scheme and Reference Architecture Model is designed to be an ¿enabling¿ structure to allow
interoperability between different commercial systems, and not prescriptive in determining any one system. It
is not frequency- nor air interface protocol-specific, provides maximum interoperability, has a high population
capability, and provides the possibility of upwards migration to more capable systems.
This International Standard provides a reference structure which enables an unambiguous identification and
also identifies the data construct as an ITS/RTTT message. This is particularly important within an EDI
environment. The construct also identifies which ITS/RTTT data structure is contained in the message.
A wide variety of applications can be supported by the structure determined in this International Standard,
such as simple AVI/AEI, complex unambiguous ITS/RTTT messages (in either user-identified or anonymous
formats), or new and as yet undefined message structures.
The principles of data element structure determined in ISO/IEC 8824 have been adopted to provide an
interoperable architecture within a standard framework. The use of Abstract Syntax Notation One (ASN.1)
from ISO/IEC 8824 and ISO/IEC 8825 as a data identifier is widely used.
A key feature of the structure is to provide interoperability of data constructs. This AVI/AEI scheme may also
be used as part of a data construct for purposes such as automatic fee collection and enables interoperability
with existing standards.
This International Standard does not include the air interface nor any implementation aspect, solely the
Reference Architectures. Subsequent International Standards will define data structures for general AVI/AEI
and for specific sectors of application.
The Numbering and Data Structure will be capable of operation both by read/write devices, and by read-only
devices where there is no requirement (or if there is no possibility) to write to the OBE.