Chapter 5: Linked Data per ISO/IEC 21972

Smart City — WIA-CITY-001

RDF/OWL ontology for city KPIs, JSON-LD context, SPARQL endpoint patterns, federated city data exchange via DCAT-AP, schema.org PlaceAction extensions.

This chapter elaborates on the Linked Data per ISO/IEC 21972 portion of Smart City (WIA-CITY-001). The smart city canonical envelope shape, API surface, and protocol exchanges are designed to interoperate across implementations published under the WIA Standards family. Each Phase file in `spec/` documents one architectural layer (envelopes, REST surface, federation, ecosystem) and the present chapter focuses on the linked data per iso/iec 21972 subset of that layering.

Implementations of linked data per iso/iec 21972 need to reconcile the per-standard expectations of ISO 37120:2018 (City indicators), ISO 37122:2019 (Smart city indicators), ISO 37123:2019 (Resilient cities indicators), ITU-T Y.4900 series, ISO/IEC 30141:2018 (IoT Reference Architecture). The Phase 1 envelope class for Smart City carries the per-host identifier and per-tenant identifier so that audit records can be reconstructed across hosts that federate through the Phase 3 protocol layer.

Operators stepping into linked data per iso/iec 21972 typically follow this trajectory: stand up the reference simulator at `simulator/index.html`, walk the canonical envelope per the CLI helper at `cli/smart-city.sh envelope`, then exercise the Phase 2 endpoints with curl/Postman against a host running the reference container at `wia/smart-city-host:1.0.0`. Once those steps complete, integrators wire the real backend one endpoint at a time per the Phase 1 §A.* envelope catalogue and the Phase 2 §B.* endpoint catalogue.

A common operational concern in the linked data per iso/iec 21972 space is observability. Every Phase 1 envelope SHOULD emit a structured log line at the host's audit transport with: timestamp per RFC 3339, host identifier, tenant identifier, envelope class, envelope identifier, operation outcome, and a W3C Trace Context `traceparent` propagated end-to-end. Phase 2 surfaces this trace identifier as the `X-WIA-Trace-Id` response header. Phase 3 protocol exchanges propagate the trace identifier inside the exchange envelope so that a federation crossing remains correlatable end-to-end.

The linked data per iso/iec 21972 portion of the standard composes with: WIA-OMNI-API for credential storage, WIA-AIR-SHIELD for runtime trust list, WIA-INTENT for workload intent declaration, and WIA Secure Enclave for sealed-data envelopes where personal data is processed. The composition lets one host running multiple WIA family standards reuse one identity, one signing-key chain, and one audit transport rather than maintaining N parallel per-standard implementations.

Normative references touched in this chapter

Implementation worksheet

  1. Read the corresponding Phase file in spec/ (Phase 1 for envelopes, Phase 2 for API, Phase 3 for protocol, Phase 4 for ecosystem).
  2. Walk the CLI helper: ./cli/smart-city.sh envelope emits a sample Phase 1 envelope.
  3. Exercise the simulator at simulator/index.html.
  4. Cross-reference the standards listed above to align with the operator's per-jurisdiction obligations.
  5. Wire the conformance suite at https://github.com/WIA-Official/wia-smart-city-conformance.

Cross-standard composition recap

This chapter, like every other Phase 1-4 chapter in the Smart City eBook, composes with the wider WIA Standards family. Implementations that adopt the canonical envelope reuse the cross-standard audit transport (W3C Trace Context plus OpenTelemetry semantic conventions), the cross-standard identity (WIA-OMNI-API), and the cross-standard runtime trust list (WIA-AIR-SHIELD) without per-standard re-implementation. The federation handshake described in Phase 3 §3 follows the same challenge-response pattern as the rest of the WIA Standards family so that one operator can federate across multiple standards using one signing-key chain and one audit transport.