OPDA Knowledge base
Concept tier foundation

Relator

opda:Relator

Relator

A Relator is a relational kind: it stands between two or more parties and carries properties that don’t belong to any single party. A Relator’s existence is founded by an external event — without that founding event, the Relator does not exist.

Why it matters

Some things in property data are best modelled as a relationship that has its own identity and its own properties. A Transaction is not a property of the Seller, nor a property of the Buyer — it is a thing-in-its-own-right that binds Seller, Buyer, and Legal Estate, and that bears its own properties (transaction-id, founding-event, status). A Proprietorship is not a property of the Person nor of the Title — it is a binding that carries its own joint-tenancy-vs-tenants-in-common discriminator.

If you have ever wanted to attach a property to “the relationship itself” rather than to either party, you wanted a Relator. The two OPDA Relators in scope are Transaction (binds Seller + Buyer + Legal Estate; founded by offer-acceptance) and Proprietorship (binds Proprietors to a Registered Title; founded by the registration activity).

Hard cases

  • Party-substitution within a Transaction. A Buyer drops out and another Buyer steps in. The Transaction Relator persists (founding event unchanged); only the bearer of the Buyer role changes.
  • Joint tenancy vs tenants in common. The discriminator lives on the Proprietorship Relator, not on the Proprietor roles. Asking “which type is the Proprietor?” is the wrong question — it is the binding that is one or the other.
  • A Relator without its founding event. Cannot exist. A Transaction without an offer-acceptance event is not a Transaction; a Proprietorship without a registration event is not a Proprietorship. The founding event is part of the IC.

Identity Criterion

A Relator’s identity is the (mediated-parties, founding-event) tuple. Two Relator records are the same Relator only if they bind the same parties through the same founding event. See the Logical tier → for the typed structure.

  • Role — Roles are borne by parties within a Relator’s context
  • Role Mixin — Role Mixins are cross-Kind Roles borne by parties within a Relator’s context
  • Transaction — the canonical OPDA Relator: binds Seller, Buyer, and Legal Estate
  • Proprietorship — binds Proprietors to a Registered Title
%%{init: {"theme": "base"}}%% flowchart LR accTitle: Relator related-Kinds neighbourhood graph accDescr: Relator as the pattern Kind specialised by Transaction (binds Seller + Buyer + LegalEstate, founded by offer-acceptance) and Proprietorship (binds Proprietors to a RegisteredTitle, founded by registration activity); hosts Role and RoleMixin instances within its context. classDef centre fill:#E1BEE7,stroke:#6A1B9A,stroke-width:3px,color:#4A148C classDef cls fill:#B3E5FC,stroke:#0277BD,stroke-width:2px,color:#01579B Relator["Relator
(pattern)"]:::centre Role["Role"]:::cls RoleMixin["RoleMixin"]:::cls Transaction["Transaction
(canonical)"]:::cls Proprietorship["Proprietorship
(canonical)"]:::cls Role -->|"sitsWithin"| Relator RoleMixin -->|"sitsWithin"| Relator Transaction -.->|"specialises"| Relator Proprietorship -.->|"specialises"| Relator

Source ODR

ODR-0006 — Agents and roles §Q3

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