Concept tier
Narrative definitions and identity criteria for the real-world objects OPDA models.
Audience: SMEs, surveyors, conveyancers
OPDA Concept Tier
This is the Concept-tier view of OPDA’s ontology — written for property-industry SMEs (surveyors, conveyancers, lenders, estate agents, government data leads, regulators). It explains what each business object means and why it is identified the way it is, without requiring you to read Turtle, JSON, or any other machine syntax.
If you have ever asked questions like:
- “When does a Property stop being the same Property?”
- “Is a Buyer one entity, or a different entity in every Transaction?”
- “What makes one Address record the same Address as another?”
then this tier is for you. Identity Criterion (IC) is the load-bearing concept: it is the answer to the question “when are two records about the same thing?” — and every entity in this tier states its IC in business language.
See also: Modelling section
The Bounded contexts (DDD) and Business glossary pages in the Modelling section are complementary editorial registers: the bounded-contexts page explains the DDD framing and industry context map that motivates this module structure; the business-glossary page is the pre-ontology SKOS seed (54 OPDA business terms + 500 schema-derived concepts) from which this tier’s entity definitions grew.
Reading order
You can read this tier top-down (a guided tour) or jump straight to the entity you care about.
For a guided tour:
- Start with foundation/ — the cross-cutting kinds (Role, RoleMixin, Relator, ValidationContext, DiagnosticExemplar, GeneratorRun) that the other modules reuse.
- Read property/ — the physical Property, the LegalEstate vested in it, the RegisteredTitle that documents it, and the Address that locates it. This is the Identity-Criterion crux of OPDA.
- Read agent/ — Person, Organisation, Proprietor, and the transactional roles Seller / Buyer.
- Read transaction/ — the Transaction Relator, its Milestones, and its position in a TransactionChain.
- Read claim/ — Claim, the three Evidence subtypes (Document / Electronic Record / Vouch), the VerificationActivity that produces a verified claim, and the AssuranceLevel + TrustFramework that scope its validity.
- Read governance/ — the DPV mapping records that link OPDA kinds to GDPR personal-data categories.
- Read descriptive/ — authority-issued artefacts (EPC Certificate, Search, Survey, Valuation, Comparable) that ride alongside a Property.
For a jump-in reader: see the entity catalogue below.
Module catalogue at a glance
The seven Concept-tier modules and their primary concerns:
Cross-cutting kinds
(Role, Relator, ValidationContext)"]:::cls Property["property
Property + LegalEstate +
RegisteredTitle + Address"]:::cls Agent["agent
Person, Organisation,
Seller/Buyer/Proprietor roles"]:::cls Transaction["transaction
Transaction Relator +
Milestone + Chain"]:::cls Claim["claim
Claim, Evidence,
Verification, Assurance"]:::cls Governance["governance
DPV mapping +
Special-category scheme"]:::cls Descriptive["descriptive
EPC, Survey, Valuation,
Search, Comparable"]:::cls Foundation -->|"reused by"| Property Foundation -->|"reused by"| Agent Foundation -->|"reused by"| Transaction Foundation -->|"reused by"| Claim Property -->|"vested rights bear"| Agent Property -->|"conveyed in"| Transaction Agent -->|"plays roles in"| Transaction Transaction -->|"claim-bearing"| Claim Property -->|"PII surfaces inform"| Governance Agent -->|"PII surfaces inform"| Governance Property -->|"riding artefacts"| Descriptive
Master entity-relationship flow
How the central OPDA Kinds connect across modules — the load-bearing joins that an integrator must understand before going further:
(Relator)"]:::rel Proprietorship["Proprietorship
(Relator)"]:::rel Seller["Seller
(RoleMixin)"]:::cls Buyer["Buyer
(RoleMixin)"]:::cls Proprietor["Proprietor
(Role)"]:::cls Milestone["Milestone"]:::cls Chain["TransactionChain"]:::cls %% Claim chain Claim["Claim"]:::cls Evidence["Evidence"]:::cls Verification["VerificationActivity"]:::cls Assurance["AssuranceLevel"]:::cls Framework["TrustFramework"]:::cls %% Descriptive ride-alongs EPC["EPC Certificate"]:::ext Survey["Survey"]:::ext Valuation["Valuation"]:::ext Search["Search"]:::ext %% Property quartet Property -->|"hasAddress"| Address Property -->|"hasLegalEstate"| LegalEstate LegalEstate -->|"documentedBy"| RegisteredTitle LegalEstate -->|"leaseTerm"| LeaseTerm %% Proprietorship binding Proprietorship -->|"bindsTitle"| RegisteredTitle Proprietorship -->|"bears"| Proprietor Proprietor -->|"borneBy"| Person Proprietor -.->|"alternatively"| Organisation %% Transaction binding Transaction -->|"conveys"| LegalEstate Transaction -->|"founds"| Seller Transaction -->|"founds"| Buyer Seller -->|"borneBy"| Person Seller -.->|"or"| Organisation Buyer -->|"borneBy"| Person Buyer -.->|"or"| Organisation Transaction -->|"hasMilestone"| Milestone Transaction -->|"memberOf"| Chain %% Claim chain Claim -->|"supportedBy"| Evidence Verification -->|"verifies"| Claim Verification -->|"uses"| Evidence Verification -->|"assigns"| Assurance Verification -->|"underFramework"| Framework Seller -.->|"attestedBy"| Claim %% Descriptive EPC -->|"concerns"| Property Survey -->|"concerns"| Property Valuation -->|"concerns"| Property Search -->|"concerns"| Property
Entity catalogue
Complete index of OPDA Concept-tier entities. Each row links to the entity’s narrative file in this tier; cross-tier traceability follows the convention /docs/manual/concept/<module>/<entity>.md.
Foundation
Cross-cutting kinds reused across every module.
| Entity | Summary |
|---|---|
| Diagnostic Exemplar | Minimal worked-example data exposing one Identity-Criterion-bearing surface for Council validation |
| Generator Run | A single execution of the opda-gen pipeline that produced a specific set of emitted ontology files |
| Relator | A relational kind that mediates two or more parties and is founded by an external event |
| Role | A role borne by a single underlying Kind (e.g. Proprietor borne by Person) |
| Role Mixin | A role borne by more than one underlying Kind (e.g. Seller borne by Person or Organisation) |
| Validation Context | The named overlay profile (e.g. BASPI5) under which a record was validated |
Property
The Identity-Criterion crux of OPDA: physical Property, the legal rights vested in it, the registry record documenting it, and the addresses locating it.
| Entity | Summary |
|---|---|
| Address | An authority-issued locator (Royal Mail / OS / HMLR / INSPIRE) for a Property |
| Lease Extension Event | A statutory lease-extension event that mutates a leasehold’s term without breaking its identity |
| Lease Term | The time interval bounding a leasehold tenure |
| Legal Estate | The bundle of legal rights vested in a Property (Freehold / Leasehold / Commonhold) |
| Property | The physical residential property — a house, flat, bungalow, or maisonette |
| Registered Title | The HMLR title-register record documenting a Legal Estate |
| UPRN Succession Event | An administrative re-numbering of a Property’s UPRN — identity persists across the event |
Agent
People, organisations, and the roles they bear in a property transaction.
| Entity | Summary |
|---|---|
| Buyer | The role borne by the party acquiring a Property in a Transaction |
| Name Change Event | A reified record of a Person’s name change — Person identity persists |
| Organisation | A corporate or unincorporated organisation party to a Transaction |
| Person | A natural person — the anchor for PII regimes |
| Proprietor | The legal owner of a Property as named in a Registered Title |
| Proprietorship | The relator binding Proprietors to a Registered Title (joint tenancy or tenants in common) |
| Seller | The role borne by the party disposing of a Property in a Transaction |
Transaction
The Transaction Relator and its lifecycle structure.
| Entity | Summary |
|---|---|
| Milestone | A point or interval in the Transaction lifecycle (instruction, offer accepted, exchange, completion, registration) |
| Transaction | A residential-property transaction binding Sellers + Buyers + Legal Estate via a founding event |
| Transaction Chain | An aggregate of dependent Transactions linked by buyer-also-seller overlap |
Claim
Verifiable claims, the evidence supporting them, the activity that verified them, and the trust framework + assurance level scoping their validity.
| Entity | Summary |
|---|---|
| Assurance Level | A quality grade on a Claim’s verification (eIDAS Low / Substantial / High) |
| Claim | A verifiable assertion supported by evidence |
| Document | A short-name alias for Document Evidence (used by worked examples) |
| Document Evidence | Paper or scanned artefacts issued by an authoritative source (e.g. grant of probate) |
| Electronic Record | A short-name alias for Electronic Record Evidence (used by worked examples) |
| Electronic Record Evidence | API-retrieved structured records from an authoritative source (e.g. HMRC tax-record API) |
| Evidence | The generic evidence supertype — three subtypes: Document, Electronic Record, Vouch |
| Trust Framework | A governance regime that scopes claim validity (e.g. the UK Property Data Trust Framework) |
| Verification Activity | The activity that produces a verified claim from evidence |
| Vouch | A short-name alias for Vouch Evidence (used by worked examples) |
| Vouch Evidence | A formal attestation by a regulated professional (e.g. SRA-licensed solicitor) |
Governance
The DPV (Data Privacy Vocabulary) mapping records that link OPDA Kinds to GDPR personal-data categories.
| Entity | Summary |
|---|---|
| DPV Mapping Record | A mapping from an OPDA Kind to its baseline personal-data category |
| Special Category Scheme | GDPR Article 10 / DPA 2018 special-category personal-data scheme |
Descriptive
Authority-issued artefacts that ride alongside a Property in a Transaction.
| Entity | Summary |
|---|---|
| Comparable | A comparable-sale or comparable-rental record supporting a Valuation |
| EPC Certificate | A DESNZ-governed Energy Performance Certificate for a Property |
| Search | A local-authority or environmental search result (CON29R, LLC1, etc.) |
| Survey | A professional property survey report |
| Valuation | A RICS-regulated professional or automated-model property valuation |
What is not in this tier
- Attribute lists, cardinalities, data types — these live in the Logical tier for engineers integrating against the model.
- Deployment topology, named graphs, derived profiles, content negotiation — these live in the Physical-Database tier for triplestore operators and SPARQL consumers.
- OWL / SHACL / SKOS / Turtle syntax — these live in the Physical-Ontology tier for ontology engineers and regulators auditing the shapes.
- UFO / DOLCE / Substance Kind / RoleMixin terminology — these are deliberately absent at this tier; they appear in the Logical tier where engineers need the formal grounding.
When this tier needs to point at typed detail, it links forward to the corresponding Logical-tier file with the convention [Logical tier →] pointing at ../../logical/<MODULE>/<ENTITY>.md (replace <MODULE> / <ENTITY> with the actual module + entity slug).
Provenance
This documentation is generated from the 8 emitted module TTLs at source/03-standards/ontology/ (foundation.ttl, opda-classes.ttl, opda-{property,agent,transaction,claim,governance,descriptive}.ttl). Each entity’s Identity Criterion and Hard Cases are lifted verbatim from rdfs:comment on the OWL class — the A9 per-kind discipline (ADR-0007) was designed so the emitted ontology carries this narrative material directly.
The ODR audit trail (docs/ontology/odr/) is not a source for this documentation — it is the Council deliberation record that ratified each modelling decision. ODR links in ## Source ODR sections are link targets only; the ODR text itself is not re-paraphrased here.
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