# Context

This document captures the domain language used in this project. Terms here are the **canonical** ones — when more than one word exists for a concept, we pick one and treat the others as aliases to avoid.

This file grows as terms are resolved during design conversations. Concepts that haven't been examined yet are not listed.

## Language

### Bulk upload

**BulkUpload**:
A user-supplied spreadsheet of addresses for a Portfolio, transformed and matched to UPRNs before being inserted as Properties. Has an explicit lifecycle from upload through finalisation.
_Avoid_: import, batch, file upload, ingest

**ColumnMapping**:
The user's declaration of which spreadsheet column means what (e.g. column "Property Address" means `address_1`). Stored as JSON on the BulkUpload row.
_Avoid_: schema, header map, field mapping

**UPRN**:
Unique Property Reference Number — the UK national identifier for an address. Address matching attaches a UPRN to each row where possible.

**Address matching**:
The pipeline stage that splits the source file by postcode, looks up UPRNs, and produces matched-address output. Triggered via FastAPI.
_Avoid_: postcode lookup, address resolution, address lookup

**Combiner**:
The pipeline stage that aggregates the per-postcode address-matching outputs into a single combined CSV in S3, ready for review.
_Avoid_: aggregator, merger

**Finalise**:
The terminal action that reads the combiner output, inserts rows as Properties on the Portfolio, and decides whether the BulkUpload needs further review.
_Avoid_: import, commit, ingest

### Landlord overrides

**Landlord**:
The housing association supplying a Portfolio's BulkUploads. A Landlord knows facts about their properties that EPC data doesn't (e.g. that a cavity has been filled), and those facts take precedence when computing an assessment.
_Avoid_: customer, client, owner, organisation (Organisation is a separate, broader entity)

**Landlord override**:
A landlord-supplied fact about a property that takes precedence over EPC-derived defaults when computing an assessment. The end-to-end Landlord override journey has two layers — a **VocabularyMapping** layer (this glossary entry below) and a per-Property fact layer (the **Property override**, below).
_Avoid_: customer data, manual override, landlord data

**Property override**:
The per-Property fact layer — one resolved fact per `(Property, Building part, component)`, where component is one of `wall_type`/`roof_type`/`property_type`/`built_form_type`. Holds a **snapshot** of the resolved enum value (a denormalised copy of the VocabularyMapping outcome at finalise time, so two Properties sharing a description can later diverge), plus the original spreadsheet text it resolved from. Materialised by the finaliser **for UPRN-matched Properties only** (v2); the resolved value is never `UNKNOWN` — the Verify step forces every `UNKNOWN` to be mapped before Finalise, and an unresolved description fails the run. See [ADR-0005](./docs/adr/0005-async-bulk-upload-finaliser.md) (table) and [ADR-0006](./docs/adr/0006-property-overrides-join-and-no-uprn-defer.md) (population).
_Avoid_: per-property mapping, property fact, override row

The Model backend consumes Property overrides at modelling time; property type (and built form when known) lets the **predict-EPC service** estimate a never-EPC'd property from surrounding homes of similar archetype.

**Source row id**:
A synthetic UUID minted per source-file row at `start-address-matching` and written into **both** the address CSV and the classifier CSV. It is the stable join key that lets the finaliser tie a row's identity (combiner output → `property_id`) to that row's raw descriptions (classifier CSV), since neither file preserves row order and `Internal Reference` is absent from the classifier CSV. See [ADR-0006](./docs/adr/0006-property-overrides-join-and-no-uprn-defer.md).
_Avoid_: row index, internal reference (a separate, optional landlord field)

**VocabularyMapping**:
The translation from a free-text description to a canonical domain enum value (e.g. `"cavity: filledcavity"` → `WallType.CAVITY`). Two producers: the `ColumnClassifier` (an LLM in the Model service — needed because BulkUpload spreadsheets contain arbitrary landlord text that must be sanitised) and the **deterministic OS-code mapping** used by the postcode-search journey (a fixed OS classification code → enum table; no interpretation involved). Stored per-Portfolio, one row per `(category, description)`. A row carries provenance (`classifier`, `user`, or `os_places`) so user overrides survive re-classification and OS-derived facts stay distinguishable.
_Avoid_: column mapping (that's a separate concept — see `ColumnMapping` above), classification, dictionary

### Postcode search

**Postcode search**:
The journey that adds Properties to a Portfolio by searching a postcode: postcodes.io validates/normalises and supplies geography (local authority, constituency), OS Places supplies the addresses (UPRN, coordinates, classification code), and the user selects which addresses to add — across multiple postcode searches in one basket, submitted once. Raw OS responses are cached per-postcode (`postcode_search`) and re-served while fresh. Creates real Properties whose energy data is absent-until-modelled (derived state, no marker column); writes property type / built form facts through the Landlord-override layers via the deterministic OS-code mapping.
_Avoid_: address import, quick add, single add

### Building parts

**Building part**:
One physically distinct part of a dwelling described by a single entry within a multi-valued cell. A dwelling is one **Main building** plus zero or more **Extensions**. Per-part descriptions appear as comma-separated entries in physical-element columns (e.g. `Walls`, `Roofs`); whole-dwelling columns (e.g. `Property Type`) carry a single entry and are **not** split per part.
_Avoid_: annexe, unit, section, dwelling part

**Main building**:
The principal building part of a dwelling — exactly one per address. The others are **Extensions**.

**Extension**:
A building part that is not the Main building, numbered **Extension 1 … Extension N-1** for an N-entry address.
_Avoid_: annexe, addition, outbuilding

**Multi-entry**:
The property of a BulkUpload row whose physical-element cells hold **more than one comma-separated entry**, one per **Building part**. Always intra-cell in our data — never multiple rows sharing one address/UPRN. Within a row, the multi-valued columns agree on entry-count, so **position `i` is the same Building part across every multi-valued column**.
_Avoid_: multi-row, multi-record, duplicate address

**Building-part ordering** (a.k.a. **ordering**):
The user's declaration, captured once per file, of which list-position maps to which Building part — because the entry order is a consistent per-file mistake (`"A, B"` could be `[Main, Extension 1]` or `[Extension 1, Main]`). Stored per entry-count as a permutation. See [ADR-0004](./docs/adr/0004-multi-entry-building-part-ordering.md).
_Avoid_: sort order, sequence, column mapping

### Scenarios

**Scenario**:
A named modelling configuration for a Portfolio — the *question* a modelling run answers (e.g. "what does it take to reach EPC C, excluding solid floor insulation?"). Captures the target, the measure constraints and the **housing type** (Social/Private — a genuine modelling input because it drives funding treatment, not portfolio metadata). **The configuration is immutable once created** — a change of mind is a new Scenario — but the *name* is a label, renameable at any time, and a Scenario that has no Plans yet may be deleted (an unasked question can be withdrawn; a modelled one cannot). Plans are generated *against* a Scenario by the modelling engine; impact/results live on the Plans (and Reporting), never on the Scenario itself.
_Avoid_: plan (a Plan is one property's modelled answer within a Scenario), simulation, run

**Goal**:
The optimisation objective of a Scenario. **Increasing EPC** targets a band (its goal value is the band letter, required). Every other goal (**Reducing CO₂ emissions**, **Energy Savings**, **Valuation Improvement**) means "improve that dimension as much as possible" — it carries **no goal value**; the only brake is an optional **Budget**, without which the engine recommends the maximum interventions.
_Avoid_: target (reserve for the EPC band specifically), objective

**Budget**:
An optional per-Scenario spending cap, denominated **per property (£)** — never a whole-portfolio envelope. Absent budget = no cap.
_Avoid_: portfolio budget (a separate concept on the Portfolio row), envelope, cost limit

**Disruptive measure**:
A measure whose installation involves major internal works for residents (internal wall insulation, solid/suspended floor insulation, room-in-roof insulation). Landlords frequently exclude them; the UI sign-posts them and the "Low disruption" quick-start excludes exactly this set. Canonical list: `DISRUPTIVE_MEASURES` in the Scenario domain model.
_Avoid_: invasive (unused here), wet trades (a narrower, overlapping set: plaster-and-screed work)

**Measure exclusion**:
A Scenario constraint that takes a measure off the table for the optimiser. The only measure-*exclusion* concept on a Scenario — there is no stored inclusion list; "only Solar PV + ASHP" is expressed by excluding everything else. An empty exclusion set is valid and means every measure is available. (Exclusions decide *which* measures are available; **Fabric first** decides the *order* they are considered — the two compose.)
_Avoid_: inclusions, allowed measures (as a stored concept — UI may present "allowed/excluded" toggles, but what's captured is the exclusion set)

**Fabric first**:
A Scenario constraint that forces the optimiser to apply every viable **fabric measure** (insulation, glazing, ventilation) before it will consider heating or renewables — the heating/renewables tier is reached only if the Scenario's upgrade target is still unmet once fabric is exhausted. Unlike a Measure exclusion (which removes a measure entirely), it constrains the *order* measures are considered, not which are on the table; the two compose (an excluded fabric measure simply isn't among those forced in). Off by default, set at creation and immutable like the rest of the config. The modelling backend owns the ordering logic and the fabric/heating split — the app only records the flag (trigger-payload field `enforce_fabric_first`).
_Avoid_: fabric only (the quick-start that *excludes* heating/renewables outright — fabric-first still allows them as a fallback), sequencing/phasing (reserve for PIBI installation order), enforce fabric first (a UI verb on the toggle, not the domain noun)

**Modelling run**:
One user-initiated act of triggering modelling: a set of Scenarios crossed with one filter-defined property selection within a Portfolio. A durable record of *what was asked* — the Run filters, the Scenarios, who triggered it, when, and the matched-property count shown at preview — so Plans can be traced back to the selection that produced them, alongside how the work is going. A Scenario is the *question*; a Modelling run *asks* it (possibly again, possibly for a different property selection). Re-running an already-modelled property appends a newer Plan; latest wins on read.
_Avoid_: job, batch, trigger request, modelling task (the pipeline's execution records)

**Run filter**:
The property-selecting constraints of a Modelling run: postcode, property type, built form, and **Tags** (each multi-select). An absent filter means *unconstrained* — "all postcodes" is the absence of a postcode filter, never an enumeration. Type and built form are the canonical enum vocabularies plus **Unknown**, which selects properties with no resolvable value at all; Tags are the Portfolio's own Tags (multi-select is **any-of**). Resolution follows the Landlord-override rule for type/built-form (an override fact beats an EPC-derived value) and a **direct membership lookup** for Tags — but in all cases the modelling backend is the single authority for resolving filters to properties (the app never re-implements the rule — matched counts come from the backend, which reads the same Tag membership the app writes). See [ADR-0013](./docs/adr/0013-tags-are-app-owned-property-groupings.md).
_Avoid_: property query, segment, search (the postcode-search journey is unrelated)

### Reporting

**Gross cost**:
The all-in price of delivering a Scenario's works: construction works + project delivery + contingency. Nothing a landlord pays for sits outside it.
_Avoid_: total cost, capex, cost of works (that's the construction line only)

**Net cost**:
Gross cost minus secured funding. The figure a board commits to.
_Avoid_: net investment, cost after grants

**Project delivery**:
The professional and management costs of delivering works, as distinct from the construction works themselves.
_Avoid_: PC cost, prelims

**Current stock**:
The reporting view of a Portfolio with no Scenario applied — every figure is Effective performance, aggregated. Also the "before" side of any scenario comparison ("Current → After scenario").
_Avoid_: baseline (reserved for property-level performance concepts), portfolio overview

### Live projects

**Project**:
A delivery programme within a Portfolio — a batch of Properties taken through retrofit together — identified by its HubSpot **project code** (`hubspot_deal_data.project_code`; a stable **project id** will replace the code once the HubSpot ops board is settled, so the code is the *current* identifier, not the essence). A Property whose deal carries no project code sits outside every Project (the "Unknown Project" grouping) and cannot be reached by selecting Projects.
_Avoid_: programme, scheme, deal group, batch (a **Batch** is a separate per-deal field)

**Bulk document download**:
An app-triggered, asynchronous assembly of a single ZIP of the documents held against a chosen set of Properties — picked as a row selection in the Documents tab, scoped by the tab's current Project/group — delivered as a time-limited link emailed to the requester (and, within the session, retrievable in-app). A selection that matches no documents produces no ZIP: it fails rather than emailing an empty archive. Properties are matched to their documents by **landlord property id**. See [ADR-0011](./docs/adr/0011-app-owned-task-marker-in-task-source.md).
_Avoid_: bulk export, document export, zip download

### Tags

**Tag**:
A user-created, coloured label owned by a Portfolio, used to form an arbitrary **group** of its Properties for bulk actions (e.g. running Scenarios over the group, or excluding it from a Reporting view). Flat (no hierarchy) and many-to-many: a Property carries zero or more Tags, and a Tag labels zero or more Properties. Distinct from a **Project** (a HubSpot-sourced grouping, at most one per Property) and from a **Scenario** (a modelling question): a Tag is an app-owned, hand-curated selection with no external source and no modelling semantics of its own.
_Avoid_: label, category, group (the group is the *effect* of a Tag, not a separate entity), segment, tag group

**Bulk tag assignment**:
Assigning one Tag to many Properties at once from a small uploaded file (CSV/Excel) of property identifiers — either **landlord property id** or **UPRN**, whichever column the file carries. Parsed and matched entirely in the app (no FastAPI pipeline); the target Tag is chosen in the upload dialog, not named in the file. An identifier that matches no Property is reported back (never silently dropped); an already-tagged match is a no-op. The parallel filter-driven path assigns a Tag to **every Property matching the current property-table filter**.
_Avoid_: tag import, bulk tagging (verb is fine; the noun is Bulk tag assignment)

## Lifecycle

A **BulkUpload** moves through these statuses:

```
ready_for_processing
  → mapping_complete         (user submits ColumnMapping; Next.js writes)
    → processing             (Address matching triggered; Next.js writes)
      → combining            (Combiner stage running; FastAPI writes directly)
        → awaiting_review    (Combiner output in S3; FastAPI writes directly)
          → finalising       (Finalise dispatched; Next.js writes via compare-and-swap)
            → complete       (Finaliser succeeded; FastAPI/Lambda writes directly)
            → failed         (Finaliser failed; FastAPI/Lambda writes directly)
```

`complete` and `failed` are terminal. `finalising` is the in-flight state of the
async finaliser (mirrors `combining`); the UI renders it as "Uploading to ARA". See
[ADR-0005](./docs/adr/0005-async-bulk-upload-finaliser.md).

Re-mapping (PATCHing `columnMapping`) is legal only in `ready_for_processing` and `mapping_complete`. Any later state rejects with 409.

**Two writers**: Next.js owns transitions out of `mapping_complete`, into `processing`, and the `awaiting_review → finalising` compare-and-swap at Finalise dispatch. FastAPI/Lambda owns `combining`, `awaiting_review`, and the terminal `finalising → complete`/`failed` — writing them direct to the DB during the combiner and finaliser runs. The BulkUpload aggregate observes both. See [ADR-0005](./docs/adr/0005-async-bulk-upload-finaliser.md).

At `awaiting_review`, **Finalise is gated** (not a new status — a precondition on the action): when classifier columns were mapped the user must acknowledge the classification-verification step, and when the file is **Multi-entry** they must confirm the **Building-part ordering**. See [ADR-0004](./docs/adr/0004-multi-entry-building-part-ordering.md).

See [ADR-0001](./docs/adr/0001-bulk-upload-state-machine.md) for the deliberate "not yet" decisions baked into this lifecycle.

## Relationships

- A **Portfolio** has many **BulkUploads**.
- A **BulkUpload** produces zero or more **Properties** when finalised.
- A **BulkUpload** has at most one **Task** (the orchestration handle for the FastAPI pipeline run); a Task has many **SubTasks** (one per pipeline stage: address matching, combiner).
- A **Portfolio** has many **VocabularyMappings** — one row per `(category, description)` it has ever encountered across all its BulkUploads. See [ADR-0002](./docs/adr/0002-landlord-override-vocabulary.md).
- A **Recommendation** belongs to exactly one **Plan**. Denormalised onto `recommendation.plan_id`; the `plan_recommendations` join table is being retired.
- A **Recommendation** has at most one **Material**. Denormalised onto `recommendation.material_id` (+ `material_quantity`, `material_quantity_unit`, `material_depth`). Historically (pre-~2023) a recommendation could carry multiple materials; ~128 such legacy rows were reconciled to one each on 2026-06-07. The cardinality guard in the backfill enforces this going forward.

### Baseline performance

**Lodged performance**:
The SAP score, EPC band, CO₂ emissions, and primary energy intensity as submitted to the government EPC register. Ground truth from the register; never modified.
_Avoid_: original performance, registered performance

**Effective performance**:
The SAP score (and associated metrics) that the modelling engine actually uses as its baseline. Usually equals Lodged performance, but differs when a Landlord override or data-quality issue makes the lodged certificate unreliable — triggering a Rebaseline.
_Avoid_: current performance, adjusted performance

**Rebaseline**:
The act of substituting a corrected set of performance metrics in place of the Lodged values. Recorded on `property_baseline_performance` with a `rebaseline_reason` enum value: `none`, `pre_sap10`, `physical_state_changed`, or `both`.
_Avoid_: override, adjustment, correction

**EPC provenance** (`epc_property.source`):
Whether a property's EPC picture is a real certificate or a gap-fill. Three values:
- `lodged` — a real, current public/landlord EPC exists.
- `predicted` — no certificate exists anywhere, so the EPC was gap-filled from nearby properties (EPC Prediction).
- `expired` — also gap-filled, but conditioned on **this dwelling's own expired certificate** from the historic register (Model ADR-0054). The gov EPC API only serves certificates registered since 2012, so a pre-2012 dwelling looks EPC-less to ingestion even though a real, stale certificate exists for it.

Independent of Rebaseline: a `lodged` property may still be rebaselined, and a gap-filled property still carries Lodged-performance figures (mirrored estimates), so the presence of `lodged_*` columns does **not** imply a real certificate — only `source = lodged` does.
_Avoid_: estimated EPC (reserve "estimated" for the UI signal), source EPC

**Predicted slot**:
`predicted` and `expired` are two flavours of one slot — a property holds at most one of them, and a re-ingestion may flip which. Every query must therefore address the **slot** (`source IN ('predicted','expired')`), never a single member: matching `source = 'predicted'` alone makes `expired` rows invisible, and since `epc_property.source` is plain `text` with no enum or CHECK constraint, nothing catches it. Mirrors `PREDICTED_SLOT_SOURCES` in the Model repo. See [ADR-0014](./docs/adr/0014-epc-cards-count-certificates-not-predictions.md).
_Avoid_: predicted source (it is two sources)

**EPC coverage** — *does any certificate exist for this dwelling?*
`lodged` **or** `expired` ⇒ yes, one does (current, or out of date). `predicted`, or no `epc_property` rows at all ⇒ no, none does.

This is a **different question** from provenance's "was the picture modelled?" — an `expired` property is gap-filled *and* has a certificate. Conflating the two is what made the reporting cards wrong: the "Homes Without an EPC" card counted every gap-fill, so homes whose only fault was an out-of-date certificate were reported as having no EPC at all. The cards partition on coverage, not on provenance.
_Avoid_: missing EPC (ambiguous — say "without an EPC" for coverage, "estimated" for provenance)
_Avoid_: estimated EPC (reserve "estimated" for the UI signal), source EPC

**Provenance signal** (UI):
What the user is told about an EPC's trustworthiness, derived from EPC provenance and Rebaseline together: **Estimated** (`source IN (predicted, expired)` — the whole predicted slot, dominant; "estimated based on nearby homes") › **Re-modelled** (`source = lodged AND rebaseline_reason != none` — effective diverged from the lodged certificate under SAP 10) › **none** (`source = lodged AND rebaseline_reason = none` — effective equals lodged). Estimated always wins when both could apply.

An `expired` property is **Estimated**: its picture was modelled, not read off a current certificate. That it *also* has an (out-of-date) certificate is a matter of EPC coverage, which the reporting cards use — not of this signal.
_Avoid_: estimation notification, banner (those are component names)

**Likely downgrade**:
A property whose Lodged band sits **above** its Effective band — a re-survey would likely certificate it lower. Judged on **band movement only**; SAP-point differences within a band don't qualify.
_Avoid_: SAP downgrade (point-level, the retired signal), at-risk property

**Likely upgrade**:
A property whose Effective band sits **above** its Lodged band — Landlord overrides or SAP 10.2 scoring improved the modelled picture, so a re-survey alone would likely certificate it higher, without works. The cheapest compliance move in a portfolio.
_Avoid_: quick win, free upgrade

## Example dialogue

> **Dev:** "If the **Combiner** finishes but the user hasn't clicked Finalise, what does the user see?"
> **Domain expert:** "The BulkUpload sits in `awaiting_review`. The frontend polls and shows a 'review and confirm' button. Nothing's been written to **Properties** yet."
>
> **Dev:** "And if **Finalise** runs and 30% of rows have no **UPRN**?"
> **Domain expert:** "Those still get imported as **Properties** — just without a UPRN — and the BulkUpload moves to `complete`. Manual cleanup happens later in the property table."
>
> _(Planned change — v3 / [ADR-0006](./docs/adr/0006-property-overrides-join-and-no-uprn-defer.md): no-UPRN rows will move to a separate staging table to be re-matched, so `property` holds only matched rows. v2 does **not** change this yet — and v2 writes **Property overrides** only for the UPRN-matched rows.)_

## Flagged ambiguities

- The portfolio **Property table**'s **Property Type**, **Built Form**, **Construction Age**, **Main Fuel**, **Wall Type**, **Roof Type** and **Heating System** columns show the **landlord-override-resolved** value — the same precedence the modelling **Run filter** applies (override fact → EPC-derived → **Unknown**) — not the raw `epc_property` value or the legacy property-row column. See [ADR-0012](./docs/adr/0012-portfolio-list-resolves-descriptors-via-override-precedence.md). All seven are also **filters**, and the per-part ones (wall/roof) read the **main building part**. Wall/Roof/Heating filter by **coarse bucket** rather than the full vocabulary — their resolved values are free-text (override vocab / EPC `epc_energy_element.description` / legacy column) with hundreds of variants, so a fixed set of prefix/substring buckets (Wall → Cavity / Solid Brick / Timber Frame / Stone / …; Roof → Pitched / Flat / Room-in-Roof / …; Heating → Gas Boiler / Community / Electric Storage / Heat Pump / …) matches them, while the columns still **display the full description**. `classifyDescriptor` is the pure twin of the SQL bucketing. Two label subtleties: **Construction Age** is an RdSAP band (e.g. "1900–1929", "before 1900"), never a single year (it was formerly the "Year Built" column); and **Main Fuel** for new-approach properties reads the EPC's `epc_main_heating_detail.main_fuel_type` (an RdSAP `main_fuel` code or an EPR string, folded to a coarse label) beneath any landlord override — it only reads **Unknown** when neither is present.
- The UI surfaces labelled **"Current EPC"** and **"Current Efficiency State"** (property table, building-passport card) show **Effective performance**, not Lodged — despite the glossary advising against "current performance" for Effective. The label is a product choice ("current" = the property's true present-day modelled state); the underlying datum is still **Effective performance**. The **"Lodged EPC"** column/badge is the only surface showing **Lodged performance**, and only when a real certificate exists (`source = lodged`).
- "Upload" is used in the codebase to mean both the file-on-S3 and the BulkUpload row. We standardise on **BulkUpload** for the row; the file is just "the source file."
- "Onboarding" appears in some route paths (`bulk_onboarding_inputs/...`) but isn't part of this glossary — we use **BulkUpload** end-to-end.
