This part of ISO 14813 provides an 'enabling' structure for use in the ITS sector. It provides a formal means to enact the ISO/TC 204 decision by resolution to use ASN.1 for data definitions within ITS International Standards. This provides a common message form to enable interoperability and reuse. It provides consistency of use so that where other aspects of ASN.1 (defined within ISO/IEC 8824 and ISO/IEC 8825), such as transfer rules, are selected to be used, they are used in a common and consistent way in order to maximize interoperability and reuse. It is important to note that this part of ISO 14813 does not require the use of ASN.1 for anything other than providing a common and flexible form of data definition and this document makes specific provision for the support of use of other extant standardized syntax notations (EDIFACT, XML, etc.) whilst maintaining interoperability and reuse by defining these practices within an ASN.1 data definition. Specific implementation requirements, other than those determined in the syntax notations identified above, are beyond the scope of this document. This part of ISO 14813 also provides a means where particular ITS sector requirements, or existent International Standards, that require particular message forms and procedures that are expressed in other notations (EDIFACT, XML, etc.), may be referenced and reused by other ITS applications. Thus it presents an unambiguous system for identifying all the different data types and describing them in ITS International Standards in a common way.