Open Property Data Association
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    Overlay profiles & gaps

    A PDTF form is its SHACL overlay (ODR-0010 / ADR-0029). The 31 overlay profiles each constrain — never declare — over one fixed class TBox. Most are thin by design (session-034): a profile binds per-leaf shapes only for the Category-G substantive attributes; the A/B/C/D/E/F leaves are carried by dct:subject + a JSON-pointer dct:source and registered in the gap register, never fabricated. A thin profile is the ratified outcome, not a defect. Per-profile binding below is read at build time from source/03-standards/ontology/profiles/*.ttl.

    1 · "A form IS its SHACL overlay"

    A class per overlay (baspi:PropertyPack, ta6:PropertyPack) was rejected unanimously (ODR-0010 / session-001 Q3): that nesting is form ergonomics, not ontology, and would let overlays declare rather than constrain, inviting identity drift across near-duplicate classes. Instead each overlay is a named, dereferenceable SHACL profile graph over the fixed TBox; composition is a documented build-step graph-union. Three interface rules bind every profile against the base shapes (ODR-0010 ↔ ODR-0013):

    1. sh:in semantics — enum members are merged (set-union of base + overlay), at build time, never by entailment.
    2. Severity floor — no overlay shape may relax a property the base shape declared sh:Violation down to sh:Warning / sh:Info (enforced by a meta-shape carrying opda:metaShapeJustification).
    3. No identity override — a profile may add presence and vocabulary constraints; it may never restate or alter a Kind's identity criterion or key (ODR-0005). Identity belongs to the rigid Kind, not to a form context.

    2 · The gap register

    The gap register is the honest accounting that turns "thin" from a smell into a ratified state. Per session-034, across 28 forms the binding split is 224 bound / 1095 GAPped leaves: only Category-G substantive attributes bind as per-leaf sh:path shapes; the rest are carried by dct:subject + dct:source and GAP-registered so the omission is recorded, not silent. A completeness claim that concealed those 1095 leaves would be a provenance lie — so the register surfaces them.

    MeasureValueSource
    Overlay profiles emitted31profiles/*.ttl (live)
    — bound (≥ 1 per-leaf shape)15live sh:property count > 0
    — thin (0 per-leaf shapes, by design)16live sh:property count = 0
    Bound per-leaf shapes (this corpus)42sum of live sh:property counts
    Gap register — bound leaves224session-034 ruling (28 forms)
    Gap register — GAPped leaves1095session-034 ruling (28 forms)

    The 42 figure is the per-leaf shapes carried inside the 31 emitted profile graphs (each profile's sh:property blocks); the 224 / 1095 figures are the session-034 leaf-level accounting across the 28 forms the register tracks. They count at different granularities and are both reported deliberately. The gap register itself is part of the custom opda-gen layer — see the custom reference rendering ↗.

    3 · oc1 / llc1 — held thin (ODR-0008d)

    oc1 (Official Copy of Register and Title Plan) and llc1 (Local Land Charges Search) are held thin under a recorded re-open trigger (ODR-0008d / session-034 Q2): they are authority-register extracts, not human-filled forms. Binding their leaves as per-leaf shapes would assert a closed-world obligation on data whose shape the register — not the OPDA model — owns. They stay thin until a named consumer issues a worked SPARQL query against a register leaf; that worked query is the trigger that re-opens the binding decision. The trigger is recorded so the thinness is governed, not forgotten.

    4 · All 31 profiles

    Every emitted profile, ordered by binding (most-bound first). baspi5 is the most-bound profile (the ODR-0010 round-trip MVP); the NTS2 specialist-issue extensions (as, dr, hs, …) are thin single-disclosure overlays. Binding and form name are read live; the source instrument is the form-question / ADR authority the profile's bound shapes cite via dct:source.

    ProfileFormBinding
    baspi5 BASPI5 7 bound
    nts2 NTS2 Material Information 6 bound
    piq PIQ Property Information Questionnaire 6 bound
    ta6 TA6 Property Information Form 4 bound
    ta7 TA7 Leasehold Information Form 4 bound
    ntsl2 NTS2 Lettings Material Information 3 bound
    rds RDS Residential Data Set 3 bound
    ta10 TA10 Fittings and Contents Form 2 bound
    con29DW CON29DW Drainage and Water Enquiry 1 bound
    fd NTS2 extension: Flood defence information 1 bound
    jk NTS2 extension: Japanese knotweed specialist issue 1 bound
    la NTS2 extension: Loft access and details 1 bound
    oa NTS2 extension: Outside areas extension for NTS 1 bound
    sf NTS2 extension: Spray foam insulation 1 bound
    sr24 SR24 Survey Report 1 bound
    as NTS2 extension: Asbestos specialist issue thin
    con29R CON29R Local Authority Search (Required Enquiries) thin
    dr NTS2 extension: Dry rot treatment specialist issue thin
    er NTS2 extension: Estate rentcharges for freehold properties thin
    fme1 FME1 Mortgage Valuation Enquiry thin
    hi NTS2 extension: Central heating installation date thin
    hs NTS2 extension: Health and safety specialist issue thin
    llc1 LLC1 Local Land Charges Search thin
    lpe1 LPE1 Leasehold Property Enquiries thin
    ma NTS2 extension: Managing agent contact details for leasehold thin
    mc NTS2 extension: Main construction type if standard form thin
    oc NTS2 extension: Other property in chain dependency thin
    oc1 OC1 Official Copy of Register and Title Plan thin
    sb NTS2 extension: Subsidence or structural fault specialist issue thin
    sl NTS2 extension: Solar panels ownership details thin
    tf NTS2 extension: Transfer fees for leasehold thin

    31 profiles · 15 bound · 16 thin. The bound profiles cite their form-question anchors (e.g. baspi5 → basp.uk/forms/baspi5#B1.3.2); the NTS2-family extensions cite ADR-0029 (overlay-emitter rollout). The shapes the profiles carry are resolved per-shape in the SHACL Play! rendering ↗.

    The base shapes these profiles compose over are on SHACL shapes; the round-trip exemplars that exercise a loaded profile (conformant + non-conformant) are on Exemplars. Governing records: ODR-0010 (overlay mechanism), ADR-0029 (emitter generalisation + rollout), session-034 (gap register + thin ruling), ODR-0008d (oc1 / llc1 held thin).

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