Overview
ISO 14827-2:2022 - "Intelligent transport systems - Data interfaces between centres for transport information and control systems - Part 2: AP‑DATEX" defines a platform‑specific model (PSM) for exchanging transport information using ASN.1 encoded payloads carried in TCP/UDP datagrams. Often referred to as DATEX‑ASN or AP‑DATEX, the standard specifies message rules, state diagrams, session handling and procedures for reliable communication between ITS centres over IP networks. Although tailored to Intelligent Transport Systems (ITS), the model is generic enough to support other IP‑based data exchanges.
Key Topics and Technical Requirements
- Platform‑specific model (PSM): Implements a platform‑independent model (PIM) approach (see ISO/TS 19468) to map functional exchange profiles to an ASN.1/TCP‑UDP implementation.
- ASN.1-based messages: Message structures and payloads are defined in ASN.1 (reference: ISO/IEC 8824‑1) with normative datagram structures described in Annex B.
- Datagram exchange patterns: Both basic pull and basic push TCP/UDP datagram exchange PSMs are specified, including message definitions, state diagrams and implementation features.
- Session and transport procedures: Rules for establishing, maintaining and terminating sessions; transport requirements; response time‑outs; retransmission and handling of duplicate datagrams.
- Publication / subscription model: Procedures for requesting information (single, registered, online/offline subscriptions), publication of payloads and optional guaranteed delivery/acknowledgement mechanisms.
- Operational utilities: Heartbeat messages, file procedures and implementation considerations for TCP/UDP over IP are covered in normative annexes.
- Supplementary artifacts: Normative annexes include message definition requirements (A), data dictionary (C), value domains (D) and protocol requirement lists (G).
Practical Applications & Who Uses It
- ITS system architects and integrators designing inter‑centre interfaces for traffic information exchange and traffic management.
- Software developers and middleware vendors implementing AP‑DATEX clients/servers, ASN.1 encoders/decoders and datagram handling stacks.
- Network engineers implementing transport profiles, session management and reliability strategies for ITS exchanges.
- Transport authorities and control centres that need standardized publication/subscription workflows for travel information, events, incidents and traffic management data.
- Consultants and standards bodies aligning legacy DATEX implementations with modern IP/ASN.1‑based exchanges (backward compatibility with earlier ISO 14827 editions is maintained).
Related Standards
- ISO/TS 19468 - PIM specifications for data exchange protocols (mapping to PSMs)
- ISO/IEC 8824‑1 - ASN.1 notation (basic specification)
- ISO 14827‑1:2005 - earlier message format (to be withdrawn)
- DATEX II - related European traffic data exchange model referenced in the introduction
Keywords: ISO 14827‑2, AP‑DATEX, DATEX‑ASN, ASN.1, TCP/UDP datagrams, ITS data exchange, transport information interfaces.
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