Agent module — relational schema

person and organisation are the substance Kinds that bear roles. proprietorship is a reified UFO Relator binding a registered title to its proprietor set. buyer, seller, and proprietor are participation tables — their identity is parasitic on a bearer plus a founding relator, so they carry no standalone identity that anything else references.

Tables

Table	Realises	Kind	Bearer / founding relator
`person`	Person	entity	—
`organisation`	Organisation	entity	—
`name_change_event`	NameChangeEvent	event	FK → `person`
`proprietorship`	Proprietorship	relator	FK → `registered_title`, `property`
`proprietor`	Proprietor (Role)	role	bearer (`person` xor `organisation`); founded by `proprietorship`
`seller`	Seller (RoleMixin)	role	bearer (`person` xor `organisation`); founded by `transaction`
`buyer`	Buyer (RoleMixin)	role	bearer (`person` xor `organisation`); founded by `transaction`
`seller_evidenced_authority`	hasEvidencedAuthority `0..*`	junction	`seller` × `claim`

Each role table (proprietor, seller, buyer) carries CHECK (num_nonnull(person_id, organisation_id) = 1) — borne by exactly one Person or Organisation.

Entity-relationship diagram

erDiagram accTitle: Agent module — entity-relationship diagram accDescr: person and organisation as bearers; proprietorship as a reified relator founding proprietor rows; seller and buyer founded by transaction; the seller-evidenced-authority junction to claim. registered_title, transaction and claim are cross-module. person { uuid person_id PK text uri UK text has_asserted_capacity boolean has_special_category_data text has_legal_basis_uri } organisation { uuid organisation_id PK text uri UK text has_asserted_capacity } name_change_event { uuid name_change_event_id PK text uri UK uuid person_id FK timestamptz at_time } proprietorship { uuid proprietorship_id PK text uri UK uuid registered_title_id FK uuid property_id FK } proprietor { uuid proprietor_id PK text uri UK uuid proprietorship_id FK uuid person_id FK uuid organisation_id FK text owner_type FK text role FK } seller { uuid seller_id PK text uri UK uuid transaction_id FK uuid person_id FK uuid organisation_id FK text has_asserted_capacity FK text has_others_aged_17_or_over FK text role FK } buyer { uuid buyer_id PK text uri UK uuid transaction_id FK uuid person_id FK uuid organisation_id FK text role FK } seller_evidenced_authority { uuid seller_id PK,FK uuid claim_id PK,FK } name_change_event }o--|| person : "associated with" proprietorship }o--|| registered_title : "binds title" proprietorship ||--o{ proprietor : "founds" proprietor }o--o| person : "borne by" proprietor }o--o| organisation : "borne by" transaction ||--o{ seller : "founds" transaction ||--o{ buyer : "founds" seller }o--o| person : "borne by" seller }o--o| organisation : "borne by" buyer }o--o| person : "borne by" buyer }o--o| organisation : "borne by" seller ||--o{ seller_evidenced_authority : "has evidenced authority" claim ||--o{ seller_evidenced_authority : "evidences"

Lookup tables

Lookup	Bound by	Members
`owner_type`	`proprietor.owner_type`	2
`role_scheme`	`seller.role`, `buyer.role`, `proprietor.role`	12
`sellers_capacity`	`seller.has_asserted_capacity`	6
`participant_status`	overlay profiles	4

Mapping notes

Roles have no identity-bearing key. buyer / seller / proprietor exist only as a (bearer, founding-relator) pairing, with two nullable bearer foreign keys and an exactly-one CHECK. RoleMixins (Buyer, Seller) are cross-sortal (Person or Organisation); Proprietor (a Role) is normally a Person, with Organisations entering through a named sub-role.
Proprietorship is a reified Relator. Joint-tenancy vs tenants-in-common is a property of the proprietorship, not of the individual proprietors; ownership is never flattened to a registered_title.owner_person_id foreign key.
Name changes preserve identity. A name_change_event row records the change; the person row persists. A new Person is never minted on a name change.
person.has_legal_basis_uri is the one column added beyond the declared logical attributes — it hosts the SHACL rule that special-category data must carry a dpv:hasLegalBasis. (registered_title, transaction, claim live in other modules.)

Cross-tier

Logical tier: agent module.