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ADR-0020: AS4 bridge for SDG-OOTS

  • Status: accepted (not implemented in gbo-demo v0.9.0)
  • Date: 2026-08-24 (ported from the reference architecture)
  • Satisfies: S08, GO pattern B, SDG regulation (EU 2018/1724)
  • Deliberation: Reference architecture v0.6.2, decision 7 and OOTS bridge (archived and unpublished)
  • Implemented in: not implemented. gbo-demo v0.9.0 has no implementation.

Context and problem statement

The Single Digital Gateway Regulation requires cross-border evidence exchange through the Once-Only Technical System (OOTS). OOTS uses eDelivery AS4 transport, OOTS-EDM payloads, and SMP discovery. This is an EU obligation, so GBO has no architectural choice here.

Decision

GBO builds an OOTS adapter at its edge. The adapter has three parts:

  • A Domibus access point receives AS4 messages.
  • An OOTS-EDM adapter maps evidence requests.
  • An FSC translator forwards the requests to bronhouders over the standard FSC and PEP-PDP chain.

The bronhouder sees a normal FSC request. AS4 exists only at the edge, in line with the national Basisinrichting OOTS.

Consequences

  • Bronhouders serve cross-border requests without work that is specific to OOTS.
  • The mapping of evidence types depends on canonical semantic models (ADR-0024).
  • The route needs a legal-basis policy path in the Gov-to-Gov style. This path is not implemented either. Risks and technical debt tracks both gaps.

Traceability

  • Open questions: Q-79