Taking Steps Towards Usability of railML® Defined Data in TAF/TAP TSI Standardised Messaging

by Sharon Király (railML.org)

In summer 2025 railML.org allocated resources to commence the mapping of the railML® 3.3 standard to the EU-mandated communication standard TAF/TAP TSI (Technical Specifications for Interoperability).

Given the goal to allows railway operators to leverage existing railML® implementations while meeting EU TSI requirements, mapping railML® to TAF/TAP TSI is a first step in exploring interoperability between systems using either standard, as well as ensuring regulatory compliance for railML® users.

TAF/TAP Explained

TAF/TAP TSI is a standard of data exchange for railway undertakings operating in the EU. Both TAF and TAP (which stands for Telematics Applications for Freight / Passengers) ensure that information can be exchanged in a consistent, structured XML format across the European railway system. Overall, TAF/TAP TSI facilitates cross-border rail operations.

The railML® to TAF/TAP Mapping Process

To ensure long-term integrity and traceability of the railML® to TAF/TAP TSI mapping, six principles were defined to guide the process:

  1. Direct element-to-element mapping shall be applied wherever possible
  2. To preserve consistency, elements may be mapped to attributes
  3. Where element semantics match, value mappings shall be applied
  4. Structural differences shall be documented
  5. Syntactic correctness and semantic validity shall be ensured
  6. Unmapped elements shall be left empty for potential future extensions

The mapping of the railML® standard to the TAF/TAP TSI undertaken so far was limited to timetable data.

Example of railML® to TAF/TAP TSI Mapping

The execution of the mapping process according to the aforementioned principles is illustrated down below using the message type PathDetailsMessage as an example.

Mapped Structure of PathDetailsMessage

However, as their structure is nearly identical, its mapping for PathDetailsMessage is also applicable for the following message types in Railway Undertaking (RU) – Infrastructure Manager (IM) communication:

  • PathRequestMessage
  • PathNotAvailableMessage
  • PathCanceledMessage
  • PathConfirmedMessage
  • PathDetailsRefusedMessage

The mapping will shortly be published on the railML 3 Wiki 3.0 under Guides and is ready for use. Still, as scope differs between the TAF/TAP TSI and the railML standard, some elements currently remain without direct correspondence or require further clarification.

As always, your feedback is greatly appreciated. Please leave your review, suggestion, critique, idea for extension or any other input in the Forum or reach out to orga@governance.railml.org.