Open Property Data Association
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    JSON-LD mappings

    Per-overlay JSON-LD @context files that map each overlay's JSON property names to ontology terms. Bridges the JSON-Schema world to the RDF world.

    See also: Ontology manual — Physical-Database tier

    The Content negotiation page in the Ontology manual covers the HTTP-layer side: how Accept: application/ld+json requests against https://opda.org.uk/pdtf/<resource> URIs resolve to JSON-LD responses, and which named graphs back those responses. This page covers the authoring of the @context files that make JSON-LD round-tripping work.

    Status

    This is a stub for upcoming work. The structure below is what we plan to populate; existing artefacts in source/ that feed it are cited inline.

    See also: RML mapping (a different mechanism)

    Mapping documents a separate, already-largely-complete mechanism — RML, used to independently verify the ontology↔schema correspondence (99.4% traced). It produces no @context file and isn't JSON-LD; this page's @context authoring work is a different, still-unbuilt effort for a different purpose (production JSON-LD round-tripping).

    What already exists

    PDTF has already started JSON-LD work — see source/03-standards/trust-framework/public/contexts/. That gives us an upstream baseline; the new work is to author overlay-specific contexts that map BASPI / TA6 / etc. property names to ontology terms.

    Approach

    Historical, unimplemented plan

    The steps below preserve the schema-derived ontology's planning record; they are not current SPDTF mapping policy. Use the Category 8 mapping method for human review, predicate selection and the required SSSOM record profile and its current implementation limits.

    1. For each overlay (BASPI v5 first), author a @context mapping JSON property names → RDF terms.
    2. Resolve cross-context concepts via skos:exactMatch when same meaning, distinct classes when different meaning.
    3. Validate by round-tripping: JSON instance → RDF → JSON, asserting equivalence.
    4. Publish contexts at stable URLs under trust.propdata.org.uk/contexts/ for production use. (That namespace sits on the legacy propdata.org.uk site, which carries OPDA copyright but was not authored or approved by OPDA — the production hosting target is not yet OPDA/MHCLG/DPMSG-ratified.)

    Worked example (BASPI v5 — first overlay)

    BASPI v5 is the candidate for end-to-end worked example because:

    • Most active overlay (current HBSG standard)
    • Has explicit human-readable spec from HBSG (the BASPI v5 doc)
    • Maps to schema.org concepts cleanly for most properties

    Targets

    Output folder: source/00-deliverables/semantic-models/mappings/.

    • baspi5-context.jsonld — first mapping (anchor example)
    • ta6-context.jsonld — second
    • nts2-context.jsonld — third (and tracks MHCLG successor)
    • ...one per overlay

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