Status: implemented

Implemented — this change has shipped.

RFC 0080: Every official asset class is a builtin; data center and manufactured housing join the builtin set

Compatibility clauses superseded by RFC 0081. §5 (the org.uwmd.data_center alias, CLS-01/CLS-02, module-gated severities), the module shells and the transition decision rows are removed, and the hotel facts consolidate into rent_roll. The builtin-class design stands.

Implemented; released in 3.0.0 with Format 2.1 and Stable Protocol 3.0.0. The maintainers accepted this direction on 2026-10-10; this RFC turns it into a contract. See Resolution.

Summary

The project ships two kinds of official asset class today:

• Ten builtins (multifamily … land), which have the full kit.
• Module classes, which do not. Data center (org.uwmd.data_center, RFC 0039) is the only one shipped; manufactured housing (draft RFC 0068) was about to follow.

Under Protocol §X.2.4 a module class gets no builtin calc pack, no Excel layout, no size-registry row and no defaults, and it carries a namespaced id. The accepted design is the opposite: every official class is equal to multifamily from the day it is added.

This RFC:

• Adds data_center and manufactured_housing to the builtin set with full standard support and full starter support (RFC 0078 D5).
• Folds the official hospitality module's content into the builtin hospitality class.
• Keeps every existing document valid. org.uwmd.data_center documents read as the builtin with a deprecation warning.
• Restricts module-declared classes to third parties.

Motivation

• The two-tier design lacked an explicit acceptance decision. RFC 0003 closed the builtin set ("answers 'what does data_center mean?' by not allowing the question"). RFC 0039 then rejected a builtin data center as "the full builtin cost — for one vertical". The 2026-10-10 product-decision audit found no acceptance record selecting either.
• Module classes are second-class in concrete ways. Per the 2026-10-10 inventory:
  • no pack, so no receipts (RCP_PACK_UNRESOLVED);
  • no size row, so CC-13 and CSV size columns do not apply and price per unit is empty;
  • no defaults, so uwmd scope fails;
  • no Excel layout;
  • no mixed-use component slot;
  • no stage overlays;
  • section schemas declared but not enforced.
• Hotel fields sit outside the standard. ADR, RevPAR and F&B live in a module (RFC 0006 Alternative 3), although hospitality is a builtin, so a hotel document's core metrics are second-class too.
• The adopter need is concrete. An adopter's park exports need a manufactured-housing class whose identity never changes, so that lake benchmark keys never split (issue #263).

Resolution

#	Direction	Source
P1	Every official asset class is a full builtin, equal to multifamily: in the asset_class list with its own calc pack, Excel layout, size registry and defaults. No official class is a module class, a namespaced id or a separate npm package. Modules exist only for third parties.	Accepted 2026-10-10
D5	"Equal" holds in both layers. Standard: class id, size metric, required sections, metric-dictionary definitions, verification rules. Starter: calc pack, Excel layout, defaults, example.	RFC 0078
M1	RFC 0068's first-scope accepted decisions carry over unchanged: weighted_pad_rent_monthly as the pad-rent representation; poh_home_rent_monthly required when park_owned_homes > 0 and absent otherwise; age_restricted, poh_rent_share, expense_ratio and the generic debt metrics deferred; nonnegative pad rent.	Accepted 2026-10-01 (RFC 0068 decision table)
M2	No promotion problem: an adopter's manufactured-housing documents must never need to change class id.	Resolution of #263, 2026-10-10

Proposed change

1. The builtin set grows by RFC, not never

• Format §2.2 / §2.2a. Twelve builtin values: the ten, plus data_center and manufactured_housing. The "closed" wording is replaced: the builtin set is the official classes, and a class joins it by RFC with full standard and starter support. Module-declared (namespaced) classes remain available to third parties for private or unofficial classes.
• Protocol §X.2.4 is reworded accordingly. Third-party module classes still get no builtin pack, layout, size row or defaults. That is now a property of unofficial classes, never of official ones.

2. Data center (data_center)

• Sections. RFC 0039's module sections (dc_capacity, dc_power, dc_revenue) become standard Format sections with their current fields, required/optional status and validation (CC-MOD-DC-01..07 renumbered into a standard family).
• Size. The primary size is commissioned critical IT load in kW. Precedent puts every builtin primary size on property (e.g. student total_beds). Add property.critical_it_load_kw, or justify reading the primary from dc_capacity and amend the registry rule; the implementation decides and records it.
• Metrics. The eleven module calculations, plus the standard metrics every income class has (cap rate, DSCR, LTV, LTC, debt yield, cash-on-cash per RFC 0079, price and NOI per unit of size), enter the metric dictionary and a data_center pack.
• Excel, defaults, example. An Excel layout, a defaults table (see Decisions), and the Mesa Gateway example restated as asset_class: data_center.
• No fallback field. A builtin needs no fallback. Readers that predate this RFC see an unknown builtin, covered under Compatibility.

3. Manufactured housing (manufactured_housing)

• Content. RFC 0068's first scope, under M1: the mhc_sites section, its six calculations and its seven rules become standard. An earlier module branch holds that work as a module; reuse its section schema, rules, tests and example.
• Size. The primary size is sites (property.total_sites, by the same precedent as data center).
• Metrics. The six RFC 0068 calculations plus the standard income-class metrics. RFC 0068 deferred the generic debt metrics only because a module could not reach them without cloning formulas. A builtin gets them from the dictionary like every other class, so M1's deferral of them is resolved, not overridden.
• Excel, defaults, example. Excel layout, defaults table, and the Desert Palms example.
• Identity. The id is manufactured_housing from the first release. Nothing ever shipped as org.uwmd.manufactured_housing, so M2 holds trivially.

4. Hospitality

The official hospitality module's sections (hotel_metrics, hotel_brand, hotel_food_beverage), its five calculations and three rules fold into the builtin hospitality class: standard sections, dictionary entries, the hospitality pack. Where the module's revpar and the pack's revpar both exist, the dictionary keeps one definition. If they differ, record both and the choice in the Decisions table.

5. Existing documents keep working

• asset_class: org.uwmd.data_center reads as builtin data_center, with a new warning (deprecated class id; use data_center). Today INVALID-ASSET-CLASS-002 would refuse it. This RFC exempts exactly the ids the project itself shipped (org.uwmd.data_center) and nothing else. Neither the document nor its digest is rewritten.
• A document whose modules list names org.uwmd.datacenters or org.uwmd.hospitality still validates. The named module is satisfied by core, which reports an informational note, not an error.
• Third-party ids ending in .data_center or .manufactured_housing become INVALID-ASSET-CLASS-002. This is a new refusal: before this RFC those names were not builtins, so such ids were ordinary module-declared classes. That includes the test-only com.example.data_center corpus: the shadowing rule is exactly what protects builtin names. Tests that used these names as a stand-in "unknown class" switch to a neutral id.

6. Packages

• @uwmd/module-data-center and @uwmd/module-hospitality stop being developed. Their content now lives in @uwmd/core.
• The release that ships this RFC publishes a final version of each that depends on the new core and declares no classes or sections of its own, so existing installs keep resolving. They leave the publish set afterwards. Deprecating the names on npm is an owner account step.
• No manufactured-housing package is created.

7. Versions

• Format 2.1. Additive: two new builtin values and new standard sections. A document using them declares uw_version: "2.1". 2.1 readers read 2.0 and 1.x unchanged.
• Protocol. The label moves at release preparation, as before. Release preparation pairs Format 2.1 with Protocol 3.0.0 and core/CLI 3.0.0; both module packages ship 0.2.0 as their final version. Released in 3.0.0.

Compatibility analysis

• Existing documents. All stay valid. org.uwmd.data_center documents gain one deprecation warning and otherwise behave as data_center, now with receipts, size and Excel support they lacked. Hospitality documents that used the module behave the same.
• Older readers (Format 2.0). A 2.1 document with asset_class: data_center or manufactured_housing is refused by a 2.0 validator (INVALID-ASSET-CLASS-001). That is the purpose of the uw_version: "2.1" declaration: a 2.0 reader recognizes a newer format instead of misreporting it.
• Third-party modules. These are unaffected, except that a module can no longer declare data_center or manufactured_housing as custom ids. The same rule already applied to every builtin name.
• Adopters. An adopter's park exports use manufactured_housing from the first release that includes this RFC. Its export refusal for manufactured housing can be lifted then.

Conformance impact

• Size intensives. Rows for both classes in the size-intensive fixtures, and the runner strings "nine classes" / "nine sized" updated.
• Tier-3 fixtures and lender check. A tier-3 fixture per new class, and each new example in the lender-only metric fixture.
• Deprecation behavior. Runtime fixtures 06–11 (data center) become builtin-class fixtures. New fixtures cover the deprecated-id warning and the satisfied-by-core module note.
• Shadowing. Fixtures prove that com.example.data_center is still refused.
• Pinned tests. Tests that pin ten classes are updated to twelve: types.test.ts, the role counts in packs.test.ts, the Excel SUPPORTED list, the CLI smoke test and the catalog test.

Reference implementation

The full touch-point inventory is in the 2026-10-10 builtin inventory: the spec lists, schemas, types.ts AssetClass and its exhaustiveness record, SIZE_INTENSIVES, packs, defaults registry, Excel layouts, the web-editor catalog, receipts.ts lookupPack, Lite aliases, the mixed-use component slot and the docs-site sample lists. Self-storage is the template, at about 1,300 new lines plus about 35 one-line edits per class.

Also in this change:

• receipts.ts lookupPack resolves all twelve classes. It currently knows five, so hospitality, senior, student, land and mixed-use receipts fail without injected packs. That is a pre-existing gap the inventory found; fix it here.
• A mixed-use component slot for data_center if precedent supports it; the implementation decides and records it.

Alternatives considered

1. Keep module classes and give them the missing machinery (packs, layouts, size rows for modules). Rejected: this keeps two tiers and namespaced ids for official classes, and P1 forbids that.
2. Equivalence aliases instead of builtins (RFC 0073). Rejected as the mechanism. Aliases only matter when an official class ships under the wrong id first. Builtins from day one remove the need, and the narrow org.uwmd.data_center exemption above covers the one id that already shipped.
3. Bundle module manifests inside core but keep them as modules. Rejected: it is still second-class, just packaged differently.

Decisions

Question	Decision	Why (precedent)
Primary sizes	Commissioned critical IT load is property.critical_it_load_kw; sites are property.total_sites. Retain the detailed section quantities and require exact equality when both are stated (CC-DC-08, CC-MH-08). Do not infer or default physical size.	RFC 0027 and every existing builtin put primary denominators on property; a mirrored quantity is an identity, not a financial tolerance.
MHC per-site input addresses	Preserve the six calculation IDs and their operations; price/site and NOI/site read the canonical property.total_sites. mhc_sites.total_sites remains the operating-count source and is checked against it. Add loan_per_site.	The size-registry denominator and pack denominator must match (RFC 0027). The carried accepted decision defines sites, not a different financial basis.
Mixed-use slots	Admit data_center with critical_it_load_kw, and manufactured_housing with total_sites; add NOI-share and explicitly allocated purchase-price intensives. New slots require Format 2.1 and retain the existing matching component_class, NOI-footing and explicit-allocation checks. Never combine their sizes into a property size.	RFC 0019 admits income uses whose stated NOI is additive; both new classes use the same EGI-minus-operating-expenses basis.
Standard income metrics	Copy cap rate, DSCR, LTV, LTC, debt yield and guarded cash-on-cash exactly from the accepted RFC 0079 dictionary. MHC generic-debt deferral is resolved by builtin support; other MHC deferrals remain.	RFC 0079 revised accepted decisions and RFC 0080 §3.
Hospitality RevPAR	Keep the builtin noi_model.income.rooms_revenue / rent_roll.available_room_nights. The module used hotel_metrics.adr * hotel_metrics.occupancy; it has different stated inputs and can differ when those inputs are inconsistent. Only the builtin formula is in the dictionary.	The established builtin definition uses stated rooms revenue and available nights; preserve existing builtin examples rather than silently changing their denominator or source.
Migrated dependencies	Inline a referenced module calculation with an explicit round(..., its round_to) wherever the module runtime previously passed its reported result to a later calculation. Preserve every original reporting precision.	RFC 0006/module runtime threads quantized prior results; Protocol §VIII.1 round reproduces that existing boundary without adding an evaluator or tolerance.
Lite bridge	New official-class summaries default to Format 2.1 and the existing nested metadata conversion; existing classes retain the Format 1.1 bridge. Explicit source versions are preserved. Admit the seven new standard section anchors without inferring missing financial facts.	RFC 0080 requires the new class ids at 2.1; RFC 0009 supplies the existing metadata reshape, while RFC 0017 existing outputs remain unchanged.
Required hotel section	hotel_metrics remains required when the document explicitly names the legacy hospitality module. Existing builtin hospitality records without that dependency continue using their standard rent-roll/NOI sections. Optional brand and F&B sections remain optional.	RFC 0080 requires existing documents to remain valid; the module's explicit section requirement is preserved without imposing it on previously valid builtin records.
Date and type checks	MHC as_of_date is presence-only, including the existing malformed-date negative controls that establish the boundary. Date validity stays a separate core follow-up. Calculation errors retain MOD-CALC-ERROR; rule evaluation type errors use MOD-RULE-ERROR; fixed field-shape defects additionally use CLS-04. Q3/Q4 and the other accepted deferrals remain outside scope.	RFC 0068 first-scope decisions and RFC 0039 runtime precedent.
Compatibility identity	Resolve exactly org.uwmd.data_center as data_center with CLS-01; never rewrite the parsed source or digest. Official module dependencies emit CLS-02 and require no external module load, including the restricted frontmatter reader's legacy id: org.uwmd.* list spelling for exactly these two shipped modules. Third-party suffix shadows newly become INVALID-ASSET-CLASS-002.	RFC 0080 narrow grandfathering, not a general equivalence or suffix-matching contract.
Standard codes	Register CC-DC-01..08, CC-MH-01..08, CC-HOSP-01..03 and CLS-01..05; class rules execute in ordinary core validation. Missing required class sections use CLS-03.	Existing closed code-family and safe-expression verification patterns.
Defaults	Propose industrial starter ranges for data-center common financial assumptions, excluding per-square-foot TI; propose multifamily starter ranges for MHC, explicitly mapping the reserve basis from dwelling to site. Every low/central/high value is a review proxy, not a claimed market estimate. No physical facts or POH rent are defaulted. The owner must review the tables at the top of the PR before merge.	RFC 0078 distinguishes starter assumptions from verification; RFC 0080 makes defaults the explicit project owner approval requirement.
Official module packages	Keep package identities, core pins and publish membership. Retain API constants and empty view exports; the 0.2.0 compatibility manifests declare no class, section, calculation or rule. Retirement and npm deprecation occur separately at release.	RFC 0080 §6 and independent package/manifest versioning.
RFC 0073	Keep it draft for third-party identity renames. Official classes no longer depend on an identity-promotion contract.	RFC 0080 Alternatives and Product principle 1.
Native block/envelope shape	New examples and new-class Lite output use canonical section_id/_meta/content wrappers with nested metadata. Mixed-use validation reads the canonical payload, preserving its matching-class and NOI-footing negative controls. The format-neutral envelope accepts both existing v1 metadata and the v2 schema; reading it normalizes metadata for eligibility without rewriting raw content or digest.	RFC 0009's one-shape rule and the existing envelope's lossless, format-neutral contract; no new representation or financial convention.
Versions	Format 2.1 authors the additive builtin/section extension and reads all previously supported formats. Keep package versions/core pins and the Protocol label unchanged until release preparation.	RFC 0080 §7 and the RFC 0072/R8 release pattern.
Stage overlays	None. data_center and manufactured_housing take the §5.1 base lists verbatim, exactly as multifamily; dc_capacity / mhc_sites are class-required (CLS-03), never substitutes for rent_roll, and a missing rent roll is DQ-06. Examples carry a real rent_roll.	Format §5.1 declares its overlay set (land, mixed_use) exhaustive and calls section reuse "the design, not a gap"; P1 forbids a weaker bar for new classes.
Pre-existing hospitality calculations	revpar (in the builtin pack before this RFC) fails uncomputed with no finding, as every builtin pack calculation does. Migrated hotel calculations emit MOD-CALC-ERROR only for documents naming org.uwmd.hospitality, where the module runtime emitted it.	§5 "behave the same": a 099e47e-valid builtin hotel record gains no error; the module's own failure reporting is kept where it existed.
Compatibility severities	CLS-04 is an error only on canonical-id Format 2.1+ documents and a warning on legacy-alias or pre-2.1 documents. Other error-severity class findings (rules, MOD-RULE-ERROR, MOD-CALC-ERROR) are warnings on pre-2.1 documents that do not name the legacy module.	§5: the module runtime never enforced the fixed field contracts (RFC 0080 Motivation: "section schemas declared but not enforced"); a warning keeps the defect visible without failing a previously valid document.
Uncomputable RevPAR with a comp set	CC-HOSP-04 warning names the missing canonical inputs; CC-HOSP-01 is not evaluated. No ADR × occupancy fallback.	The RevPAR decision above keeps one definition; inventing a fallback is a numerical convention requiring approval (AGENTS.md: never guess at numerics). The CC-HOSP family is the existing registered home.
Scope identity and citations	uwmd scope reports the resolved builtin as asset_class / defaults_table, the stated alias unmodified as declared_asset_class, and each default's citation (additive; also on ResolvedValue).	§5 never rewrites the source; RFC 0078 starter defaults are proxies whose basis must stay visible.
Data-center expense ratio	No noi_model.expense_ratio default (accepted decision 2026-10-10). The cascade falls through as for land; no other class's table is borrowed.	Rationale: the industrial NNN proxy does not fit a power-grossed-up basis (Mesa runs 0.595). Land/mixed-use omissions are the precedent.
Grouping keys	Batch filters/summaries and lake indexed asset_class columns use the resolved builtin; index entries and envelopes keep the stated id.	M2 / issue #263: benchmark keys must never split; §5 forbids rewriting the source.

Implementation record

Accepted with its implementation in PR #302 (merging it was the acceptance, as for RFCs 0064, 0065 and 0072); implemented 2026-10-11; released in 3.0.0 with Format 2.1, Stable Protocol 3.0.0 and core/CLI 3.0.0 (release preparation PR #305). The binding direction is P1, D5, M1 and M2 under Resolution; the implementation choices are the Decisions table. The two items held for owner review at merge were settled there: the data-center and manufactured-housing defaults were proposed with sources as review proxies (see the Defaults and Data-center expense ratio rows), and RFC 0073 stays a draft for third-party identity renames. Both official module packages shipped their final 0.2.0 shells, declaring nothing, and were deprecated on npm on 2026-10-11, completing §6.

Prior art

• The builtin classes themselves. Self-storage (added after the first six) is the template for adding a class with full support.
• XBRL taxonomies. New industries extend the standard taxonomy through the standard's own process, rather than living as permanent private extensions.