Open Property Data Association
Smart Property Data Trust Framework
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    Classes

    The 41 OWL classes in the schema-derived ontology, grouped by bounded-context module and listed with each class's rdfs:comment — sourced from the SPARQL-extracted ontology model (ADR-0044). The classes are kept deliberately few and rigid (every type that merely varies is a coded SKOS value, not a subclass — see the classification doctrine). Each class links to its own page at /pdtf/{LocalName} — the canonical, dereferenceable reference with its incoming and outgoing connections, attributes, governing shapes and provenance.

    The Lease Term class is the case-independent exception: its representation is at /pdtf/classes/lease-term.

    Each section opens with its class diagram (same conventions as the interactive graph): the context's own classes and the object properties relating them, with classes from other contexts they reference pulled in with a muted border.

    Foundation · 7 classes

    UFO meta-classes + provenance/validation units shared across modules (ODR-0004 / ODR-0009 / ODR-0011).

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    ClassDefinition (rdfs:comment)
    Descriptive Property Meta-class marking an owl:DatatypeProperty as an ODR-0008 'Property descriptive attribute' — a flat, declare-once fact attaching to opda:Property / opda:LegalEstate or to one of ODR-0008's own Q4a class promotions (Search, Valuation, RiskAssessment, and their supporting structures). Per ODR-0008 §Q7a Test 1, the base TBox/shapes graph MUST NOT carry a sh:minCount on any opda:DescriptiveProperty-typed predicate: cardinality is 0..* in the base, with per-form sh:minCount variation expressed only in the ODR-0010 overlay profile shapes. Not applied to SKOS-Concept-valued or MonetaryAmount-valued descriptive facts (those are owl:ObjectProperty, outside Q6a's 'datatype property' floor) nor to ODR-0015 address/identity properties, ODR-0022 Category A/D cross-cutting reusable properties (disclosureDetail, price), or structural join predicates.
    Diagnostic Exemplar Informational endurant. IC: the named hard case — minimal Turtle exposing one IC-bearing surface as input to a Council session's identity-criterion validation. Hard cases: registered freehold house; unregistered house pre-first-registration; flat with split UPRN.
    Generator Run Information particular. IC: a single execution of the opda-gen pipeline that produced a specific set of emitted TTL artefacts. Carries the generator version (opda-gen-<semver>), the source commit SHA, and the emission timestamp. Per ODR-0004 §6a, every emission is reproducible from the recorded (version, commit) pair.
    Relator UFO Relator — a relational endurant that mediates two or more bearers and is founded by an external event. The Relator carries its own identity (the (mediated-bearers, founding-event) tuple) and bears properties that don't belong to any single mediated Kind. OPDA Relators in scope: opda:Transaction (founds Seller / Buyer RoleMixins per ODR-0007 §Q1); opda:Proprietorship (binds Proprietor Roles to a RegisteredTitle per ODR-0006 §Q3).
    Role UFO Role — anti-rigid, sortal role. An instance of a Role is borne by a bearer drawn from a single substantial Kind (e.g. Proprietor is borne by a Person — or by an Organisation under a named specialisation, but never simultaneously). A Role NEVER supplies its own identity; it borrows identity from its bearer (ODR-0005 Anti-pattern §3 — never key a Role). Per ODR-0006 §Q2.
    Role Mixin UFO RoleMixin — anti-rigid, cross-sortal role pattern. An instance of a RoleMixin is borne by a bearer drawn from more than one substantial Kind (e.g. Seller may be borne by Person OR Organisation). Distinguished from `opda:Role` (which is sortal — borne by a single Kind). Per ODR-0006 §Q2 Role layer.
    Validation Context Reification of an overlay-profile validation context per ODR-0010 §Q1 (Guarino withdrawal condition). Each instance carries five properties: opda:profileURI, opda:requires, opda:overlaysContext, opda:sourcedFrom, opda:formVersion. Anchors per-profile cardinality/enum constraints in a named context — converting conditionality from 'required (depending)' to 'required relative to a named, dereferenceable context'. ADR-0013 emits per-profile instances under <https://opda.org.uk/pdtf/Baspi5ValidationContext> etc.

    Property & land · 6 classes

    The identity crux — three Substance Kinds plus succession events and address (ODR-0005 / ODR-0015).

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    ClassDefinition (rdfs:comment)
    Address Socially-recognised locator constructed by an authority (Royal Mail / OS AddressBase / HMLR / INSPIRE) and persisting as a record-entity in that authority's stewardship. UFO Substance Kind; DOLCE NonPhysicalEndurant. IC over five hard cases per ODR-0015 §3a: cosmetic re-format; authority-internal succession; cross-variant identity-claim never collapses; Property-side change; INSPIRE-only locatedness. NOT a Mode (S015 Q1 commitment).
    Lease Extension Event Reified PROV-O activity recording a statutory lease extension (LRHUDA 1993 in England & Wales). Mutates the LeaseTerm of an existing leasehold LegalEstate (ODR-0005 §3b Rule 1 — LegalEstate identity PERSISTS through extension; rights-bundle is modified, not dissolved) and updates the RegisteredTitle's registry record. The same node may co-type as opda:Transaction (S007 Q1 Transaction-as-Relator); the dual typing reflects the property-lifecycle vs relator perspectives on the same event.
    Lease Term OWL-Time ProperInterval representing a leasehold term. Carries time:hasBeginning + time:hasDurationDescription (or time:hasEnd) per S007 Q5. Belongs to opda:LegalEstate of leasehold tenure (opda:leaseTerm join predicate). Modified by opda:LeaseExtensionEvent on statutory extension — extension produces a successor LeaseTerm with prov:wasDerivedFrom chain.
    Legal Estate Legal rights-bundle vested in a Property. UFO Substance Kind; DOLCE NonPhysicalEndurant (Searle 1995 legal-institutional object). IC: rights-bundle persistence — same individual through grant, transfer, registration, and discharge events; distinguishable from coexisting RegisteredTitle and physical Property by extent of property rights. Hard cases: tenure change; lease grant; lease termination; commonhold conversion; first registration of pre-existing common-law estate.
    Property Physical property. UFO Substance Kind; DOLCE Endurant / PhysicalObject. IC: spatial-material continuity with Kendall+Davis legal-record-discontinuity-override hybrid (ODR-0005 §3a). Hard cases: demolition; subdivision; merger; replacement; first-registration; flat with split UPRN.
    Registered Title HMLR title-register record. UFO Substance Kind (informational); DOLCE NonPhysicalEndurant. IC: title-number lineage + registry-event history (every lifecycle event captured as a reified prov:Activity with explicit prov:wasDerivedFrom / prov:wasInvalidatedBy triples). Hard cases: first registration (title opening); title closure; title merger; transfer between registers; title reissue on corrupt-plan replacement.

    Agents & roles · 7 classes

    Person / Organisation Kinds and the Seller / Buyer / Proprietor roles founded by Relators (ODR-0006).

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    ClassDefinition (rdfs:comment)
    Buyer UFO RoleMixin (anti-rigid; cross-sortal — borne by Person OR Organisation). Founded by an opda:Transaction Relator. The Buyer role of one transaction may correspond to the Seller role of the next in a TransactionChain (cf. exemplar chain-of-transactions.ttl).
    Name Change Event Reified PROV-O activity recording a Person's name change (deed-poll, marriage, gender recognition, etc.). The Person's identity PERSISTS through the name change per S006 Q1 — one Person individual with a name-attribute provenance chain via prov:wasRevisionOf, NOT two distinct Persons. Anti-pattern: owl:sameAs across the former/current names (cross-context inference propagation).
    Organisation No DPV class-level PII baseline for opda:Organisation per ODR-0006 §Q6 + ODR-0018 §Rule 4. Organisations are not data subjects; the sole-trader / individual-director surface produces an opda:Person co-annotation (linked via the actor's ownership / control relationship), not an Organisation co-annotation.
    Person Natural person. UFO Substance Kind; DOLCE Endurant. IC: FIBO-style multi-identifier persistence (date-of-birth + state-issued ID + name) over name-change, gender-recognition, and death hard cases. Anchors PII regimes (DPV co-annotation lands per ODR-0018 in opda-annotations.ttl; ADR-0012 emits).
    Proprietor UFO Role (anti-rigid; sortal — borne by Person; sub-Role for Organisation-proprietorship under a named specialisation). Founded by an opda:Proprietorship Relator (ODR-0006 §Q3 Role layer). NEVER keyed (per ODR-0005 Anti-pattern §3 — a Proprietor has no identity qua Proprietor; identity borrows from bearer).
    Proprietorship UFO Relator (relational endurant) mediating Property + Proprietor instances against a RegisteredTitle. IC: the (Title, Persons-set) tuple per S006 Q3. Joint-tenancy vs tenants-in-common is a property of the Relator, NOT of the Roles. Founding event recorded via prov:wasGeneratedBy on the registration activity.
    Seller UFO RoleMixin (anti-rigid; cross-sortal — borne by Person OR Organisation). Founded by an opda:Transaction Relator (ODR-0006 §Q2 + ODR-0007 §Q1). An instance of opda:Seller is borne by a specific Person or Organisation in the context of a specific Transaction; the role identity is parasitic on the (Transaction, bearer) tuple.

    Transaction & lifecycle · 3 classes

    The Transaction Relator, milestones, and chains (ODR-0007).

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    ClassDefinition (rdfs:comment)
    Milestone Transaction lifecycle milestone. UFO Event particular; PROV-O Activity. Hybrid PROV-O typing per S007 Q2: instant milestones (instruction, offerAccepted, exchange) carry prov:atTime; interval milestones (completion-process, registration-process) carry prov:startedAtTime + prov:endedAtTime per Moreau W3C-grade discipline. Each Milestone Activity may pair with a prov:Plan carrying opda:plannedAtTime for expected-vs-actual variance (S007 Q6 Plan-vs-Activity reification).
    Transaction Property-transaction Relator. UFO Relator (relational endurant). FIBO Arrangement precedent. Founds opda:Seller and opda:Buyer RoleMixins (ODR-0006 §Q2). IC: 5-tuple (LegalEstate-concerned, Sellers-set, Buyers-set, transaction-id-lineage, founding-event). Hard cases per S007 Q1: party-substitution; estate-change; transaction-id reissuance; chain-link-break; aborted-transaction. Carries transactionId via dct:identifier and external-system refs via opda:externalIds.
    Transaction Chain Aggregate of dependent Transactions linked by buyer-also-seller participant overlap. S007 Q4 dual-mechanism: (a) recursive opda:dependsOnTransaction predicate between Transactions; (b) opda:chainMembers list-of-Transactions on a TransactionChain parent. Chain-length cap: sh:maxInclusive 7 per CLC data (ADR-0012 emits the SHACL constraint). Chain status is derived (any-blocked → chain-blocked).

    Claims, evidence & provenance · 6 classes

    PROV-O-backed Claim / Evidence (RoleMixin) / verification structures (ODR-0009).

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    ClassDefinition (rdfs:comment)
    Attached Document A document attached to a transaction record (e.g. the registry additionalDocuments[] filed against a title to be sold). UFO Information Object; PROV-O Entity. A NEUTRAL document Kind — NOT evidence: it bears filing metadata (opda:documentDate / opda:documentTypeCode / opda:filedUnder / opda:retrievedOn) without the eIDAS-assurance commitment a document playing the evidence role carries (ODR-0024 R7 / session-028 Q7 — entailing every attached doc is Substantial-tier evidence). IC: individuated by its content + issuing activity (the artefact the registry holds), NOT by documentTypeCode / documentDate (mutable descriptive facets, not an identity principle). A document BECOMES evidence by playing the evidence role — recorded as opda:evidenceType 'Document' on an opda:Evidence (ODR-0027 §R6), NOT by an rdfs:subClassOf into evidence; an attached document stands as evidence only under ODR-0009, never by mere attachment.
    Claim Verifiable claim entity. UFO Information particular; PROV-O Entity. Per S009 Q1 80%-PROV-O mapping. Hard cases: contested assertion (multiple verifications with divergent verdicts); multi-method verification (electronic-record + vouch corroboration); assurance-level downgrade (vouch-only evidence caps at eIDAS Low).
    Evidence Evidence supporting a Claim. UFO RoleMixin (anti-rigid, cross-categorial — a bearer is evidence only qua a VerificationActivity using it; ODR-0006 Seller/Buyer pattern); PROV-O Entity. Evidence KIND is a coded isMemberOf classification — opda:evidenceType over opda:EvidenceMethodScheme (the OIDC4IDA evidence.type value-space: Document / Electronic-Record / Vouch) — NOT a subclass tree (ODR-0027 §R6; the former …Evidence subclasses are retired, since 'evidence is a role a document plays' and a Role is never rdfs:subClassOf a Kind). The three kinds are NOT collapsed (S009 R5): they remain distinct scheme concepts. Kind-specific attributes (opda:attestedBy for vouches; document/record specifics) are facets borne by the role; per-kind obligations are validated VALUE-KEYED by opda:EvidenceFacetShape (sh:targetSubjectsOf opda:evidenceType + sh:or material implication; ADR-0012).
    Trust Framework Trust framework citation — a governance regime that scopes claim validity (e.g. the UK Property Data Trust Framework). Per S009 5-residue mapped to dct:conformsTo on the verification activity (NOT a PROV-O primitive). Authoritative within scope per Session 003c Item 3 (OPDA TF authoritative scope).
    Verification Activity Verification activity recording the production of a verified claim from evidence. PROV-O Activity. The OIDC4IDA single 'time' is the completion instant → prov:endedAtTime. Uses qualified form prov:qualifiedAttribution → prov:Attribution with prov:hadRole so validation_method / verification_method are not discarded.
    Verifier The agent (organisation or person) that performs a verification, attributed via the qualified form prov:qualifiedAttribution -> prov:Attribution with prov:hadRole (ODR-0009 §Q1) — not the binary prov:wasAttributedTo/wasAssociatedWith shortcuts, so validation_method/verification_method are not discarded. A verifier organisation is a prov:Organization; a human voucher a prov:Person.

    Governance · 3 classes

    DPV mapping records and the special-category PII scheme (ODR-0012).

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    ClassDefinition (rdfs:comment)
    DPV Mapping Record Mapping record from an OPDA Kind class to its DPV baseline personal-data category and optional variant-conditional refinements. UFO Information Particular. Per ODR-0018 §Rule 4 + ODR-0012 §Evidence co-annotation, ODR-0012 is the authoring authority — this module emits the mapping records; ADR-0012 emits the resulting DPV co-annotation triples into opda-annotations.ttl (three-graph separation).
    DPV Mapping Refinement A variant-conditional specialisation of a DPVMappingRecord: applies when a Kind's variant predicate takes a specific value (opda:variantPredicate/opda:variantValue), overriding the baseline lawful basis with its own (opda:lawfulBasis). Per ODR-0018 §3a's mapping-table pattern.
    Article 10 Special Category Personal Data Scheme GDPR Article 10 / DPA 2018 special-category personal-data scheme — flags PII categories with elevated lawful-basis discipline (caution-or-conviction; AML-result; etc.). Per S012 Q3 (Baker) the scheme structure is class-declared here; the scheme instance + members emit via ADR-0010 SKOS substrate when downstream demand materialises. Currently a class declaration only — member emission deferred per ODR-0011 §Operational specifications (no S012 Q3 enum currently scoped).

    Descriptive attributes · 9 classes

    Authority-retrieved Information Objects and value structures — EPC, survey, valuation, search (ODR-0008).

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    ClassDefinition (rdfs:comment)
    Comparable No DPV class-level baseline; PII coverage flows transitively via the linked opda:Property (which carries the postal-address baseline). Per ODR-0018 §Rule 1: only direct PII-bearing Kinds declare a baseline; transitively-linked Kinds do not duplicate the upstream baseline.
    EPC Certificate Energy Performance Certificate — DESNZ-governed authority-retrieved artefact. UFO Information Object (a certificate is an information artefact, NOT a Substance Kind, per ODR-0008d Rule 3 A9 retro-correction); PROV-O Entity. Class-promoted per S008 Q4 three-criterion test: authority-retrieved provenance (DESNZ register); distinct lifecycle (10-year validity; supersession on re-assessment); distinct PII regime per ODR-0018 (address + owner-identifiable).
    Monetary Amount A monetary amount as a value structure: a magnitude (opda:amount, xsd:decimal) in a currency (opda:currency, an opda:CurrencyScheme ISO-4217 concept). UFO: a quality value / abstract value structure — NOT an endurant with independent existence and NOT a Quality of any bearer. IC (by-value): two opda:MonetaryAmount nodes denote the same amount iff equal magnitude AND equal currency. Reused as the rdfs:range across the distinct per-economic-kind monetary properties (annualGroundRent / annualServiceCharge / rent / holdingDeposit / securityDeposit / fees / estimatedPrice / soldPrice / listPrice / …), each bound to its OWN bearer — reuse the value type, NEVER the bearer (session-028 Q3 / ODR-0024 R3, Guizzardi-required). Distinct from the Category-D fixtures opda:price (a single-currency interim decimal scoped to fixtures-and-fittings only, ODR-0022 §4/§1/G1). Follows the FIBO / schema.org MonetaryAmount pattern (amount + currency).
    Nearby Facility A point-of-interest near the Property — a school, health-care facility, or transport node listed in propertyPack.nearbyFacilities for amenity context. UFO Substance Kind: a mind-independent social-physical endurant with its own identity criterion (a real-world facility persists through renaming, re-rating, and change of operator), distinct from the Property being transacted — NOT a Quality of opda:Property, since the same facility neighbours many properties (ODR-0024 R4 / session-028 Q1). Warranted on that UFO Substance-Kind basis, NOT ODR-0008 §Q4a (a provenance / lifecycle / PII test whose promotions are all Information Objects, which does not license a real-world facility). The genus bears all band attributes for the first cut (school / health-care / transport), band-scoped via SHACL in the overlay profiles; the per-band subkind split is held-as-live (Guizzardi dissent). Bears opda:distanceInMiles (proximity to the Property).
    Risk Assessment Per-peril authority-retrieved search / environmental result (the six-field block riskIndicator / actionAlertRating / result / summary / recommendations / datasetAttribution recurring across the environmental perils and CON29-style local searches). UFO Information Object (a report — an information artefact existentially dependent on its generating activity; NOT a Substance Kind and NOT a Quality of opda:Property, ODR-0008d Rule 1a); PROV-O Entity. IC (Rule 1b): individuated by the tuple ⟨generating activity (prov:wasGeneratedBy), source peril/dataset, subject property, generation time (prov:generatedAtTime)⟩ — identity grounded in the activity, not the result values. Hard cases: a re-run search is a DISTINCT RiskAssessment (new activity + generatedAtTime), prov:wasDerivedFrom the prior; two providers' assessments for one property are distinct (distinct prov:wasAttributedTo); a riskSubcategories[] entry is itself a leaf RiskAssessment (opda:hasSubAssessment); otherEnvironmental is a valid leaf with optional Qualities absent. One class instantiated per peril, NOT 12 subclasses and NOT 72 datatype properties.
    Room Dimension A room's dimensions as a value structure — a length + width (xsd:decimal, metres) and a non-rigid roomName, one per room in a Property's roomDimensions.rooms[] repeating group. An ANONYMOUS by-value structure (no identity criterion, no key — individuated by its values), NOT a Substance Kind: Council session-030 ruled neither opda:Room nor opda:Building earns a class (Room has no data-realisable identity — roomName non-rigid, no positional token; opda:Building's +O IC via the ODR-0005 §3a-4 Replacement witness is genuine but latent). Reuses the opda:MonetaryAmount by-value pattern (ODR-0024 R3); attached to opda:Property via opda:hasRoomDimension (characterisation, NOT parthood — no mereology, no transitivity). Re-homes losslessly onto a future opda:Room/opda:Building if an identity fact ever earns the Kind.
    Search No DPV class-level baseline; PII coverage flows transitively via the linked opda:Property (which carries the postal-address baseline). Per ODR-0018 §Rule 1: only direct PII-bearing Kinds declare a baseline; transitively-linked Kinds do not duplicate the upstream baseline.
    Survey No DPV class-level baseline; PII coverage flows transitively via the linked opda:Property (which carries the postal-address baseline). Per ODR-0018 §Rule 1: only direct PII-bearing Kinds declare a baseline; transitively-linked Kinds do not duplicate the upstream baseline.
    Valuation No DPV class-level baseline; PII coverage flows transitively via the linked opda:Property (which carries the postal-address baseline). Per ODR-0018 §Rule 1: only direct PII-bearing Kinds declare a baseline; transitively-linked Kinds do not duplicate the upstream baseline.

    Browse by UFO meta-category

    The classes also group by their UFO foundational meta-category — the structured opda:ufoCategory facet (ODR-0011 §8a), the "facets, not subclass trees" view of the classification doctrine.

    Comparison renderings

    The native per-class pages above are the authoritative reference (ADR-0044). The bake-off (ADR-0041) OWL tools remain available as comparison extras — pyLODE as the best single-file term reference, WIDOCO as the richest publishable shell with VOWL diagrams.

    RenderingWhat it givesOpen
    pyLODE Best single-file OWL term reference — every class & property with axioms inline. View pyLODE ↗
    WIDOCO Richest publishable shell — metadata, cross-reference, WebVOWL diagrams. View WIDOCO ↗
    Ontospy Multi-page OWL browser with per-class pages and visualisations. View Ontospy ↗

    Why the classes are shaped this way: the UFO meta-category legend and Identity & classification. See also Properties and Vocabularies (SKOS). Full index: Index & glossary.

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