OPDA Knowledge base
Concept tier descriptive

Comparable

opda:Comparable

Comparable

A Comparable is a comparable-sale or comparable-rental record supporting a Valuation — typically sourced from Land Registry Price Paid Data or VOA records.

Why it matters

Valuations rest on comparables. A Valuation that names no comparables is opaque; a Valuation that names its comparables is auditable. OPDA models Comparable as a first-class Kind so the link from a Valuation to its supporting evidence is queryable, and so the comparables themselves can carry their own provenance (Land Registry record-id, VOA record-id) and lifecycle.

If you are a valuer or auditor following the evidence chain behind a Valuation, this is the entity that closes the loop.

Editorial note. The hard cases below are interpretive — derived from the S008 Q4 three-criterion test recorded in the source TTL’s rdfs:comment, not lifted verbatim. Council ratification of a definitive hard-case enumeration for this descriptive Kind is pending.

Hard cases

  • Stale comparable. A Land Registry record from years prior used in a current Valuation. The Comparable persists; its age is a property of the record that consumers can weight.
  • Comparable in a different sub-market. A Comparable from a different street, building type, or condition class. The model carries the Comparable but exposes its differentiating attributes for the consumer to assess relevance.
  • Withdrawn or amended source record. Land Registry updates a Price Paid Data record. The Comparable can be refreshed (new record version) or retained as a snapshot — the IC discriminates by record-id + retrieval date.

Identity Criterion

A Comparable is identified by its (source-authority, record-id, retrieval date) triple. Two records refer to the same Comparable only if all three coincide. See the Logical tier → for the typed structure.

  • Valuation — Valuations cite Comparables as supporting evidence
  • Property — Comparables are related to (but distinct from) the Property being valued
%%{init: {"theme": "base"}}%% flowchart LR accTitle: Comparable related-Kinds neighbourhood graph accDescr: Comparable as a sourced sale or rental record (Land Registry Price Paid or VOA) cited by a Valuation as supporting evidence; the source Property is distinct from the Property being valued. classDef centre fill:#E1BEE7,stroke:#6A1B9A,stroke-width:3px,color:#4A148C classDef cls fill:#B3E5FC,stroke:#0277BD,stroke-width:2px,color:#01579B Comparable["Comparable
(LR / VOA)"]:::centre Valuation["Valuation"]:::cls Source["Property
(source of Comparable)"]:::cls Target["Property
(being valued)"]:::cls Valuation -->|"cites (0..*)"| Comparable Comparable -->|"sourcedFrom"| Source Valuation -->|"concerns"| Target

Source ODR

ODR-0008 — Property descriptive attributes §Q4a

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