A claim or premise embedded in a public plan, policy, inventory, program, APR, capital plan, infrastructure plan, or related document. The project tests assumptions for current plausibility under changing conditions.

The project's core move is testing whether assumptions embedded in plans still hold under changing real-world conditions. Assumption is the load-bearing interpretive primitive in v0 planning.

An Assumption is not necessarily tied to a single site or project. Manual chain extraction has pressure-tested the per-site framing and surfaced that some assumptions operate at scales other than the site. Assumptions may attach to:

• a specific site (e.g., an opportunity-site capacity assumption);
• a specific project (e.g., a project's delivery expectation);
• a typology or corridor (e.g., expected redevelopment across a class of sites);
• a program or policy (e.g., expected outcomes from a rezoning ordinance);
• an aggregate strategy (e.g., total ADU / small-infill production assumed across many parcels at once).

The ontology should not force per-site framing on aggregate strategies. A residential parcel's individual capacity assumption may be effectively zero or fractional while the aggregate strategy that includes it carries meaningful weight. The chain should be able to test assumptions at the scale they were stated.

Prototype source contact has confirmed that a single interpretive case can carry per-site, per-project, and aggregate-level assumptions simultaneously; the per-scale hierarchy is operational, and collapsing to a single scale loses interpretive coherence.

A public-data observation that bears on whether one or more assumptions remain supported, weakened, contradicted, or uncertain. A signal is source-anchored (cites a public document or dataset), assumption-anchored (only counts as evidence about a specific assumption), directional, and typed. A row in a permit database is not a signal; the interpretation that the row's content weakens or supports a specific assumption is the signal.

Signal aggregation. Multiple similar raw records may be summarized as one ImplementationSignal where they support the same interpretation about the same assumption — for example, a series of related permit records that collectively bear on a single assumption can be summarized as one signal rather than recorded as many separate signals. Source and provenance remain inspectable: the summary signal cites the underlying records. The choice between per-record signals and summary signals is operational and depends on whether the underlying records carry distinct interpretive force. The chain does not require one signal per raw row.

Candidate signal subtypes. Signal subtypes are operationally useful for categorizing signals but are not final schema doctrine in v0. Candidate subtypes — surfaced by grounding-note context and by manual chain extraction — include:

• AdministrativeSignal — pipeline / planning / case-management activity.
• PermitSignal — building-permit activity.
• PipelineSignal — project-status changes.
• MarketSignal — market-level indicators.
• InfrastructureSignal — capital plan or infrastructure-capacity signals.
• EnvironmentalSignal — environmental review or constraint signals.
• ParticipatorySignal — public-input signals (per grounding-note v7; reserved by default in v0).
• EnforcementPromptedSignal — permits or activity prompted by enforcement actions rather than voluntary market activity.
• CurrentUseSignal — signals about the current operating use of a property (e.g., active commercial tenancy at a site flagged for residential redevelopment).
• ProgrammaticTemporalSignal — signals about the implementation environment rather than the site (e.g., long approval cycles, citywide entitlement-stage stalls).

These subtypes are candidates, not final schema. Prototype source contact in v0 has operated against CurrentUseSignal and ProgrammaticTemporalSignal as load-bearing subtypes; both are retained. The list as a whole remains candidate-level and may consolidate, split, or be renamed as further prototype work accumulates.

The interpretive synthesis produced by comparing one or more assumptions against implementation signals. A finding carries direction, confidence, possible intervention candidates, and source provenance. Findings are the project's primary interpretive artifact; the Housing Element Implementation Risk Brief is a curated presentation of findings (see report-outline.md).

Three-layer assessment treatment. The method operates with three distinct assessment layers; they are deliberately not collapsed into a single direction value:

1. Signal-level direction. An ImplementationSignal's direction relative to the assumption it anchors to. Working vocabulary: supports / weakens / contradicts / uncertain.
2. Matrix row-level assessment. The matrix row's reading of one document-claim against its supporting and weakening evidence (see the Living Implementation Consistency matrix in methodology.md). Working vocabulary: confirmed / weakened / contradicted / unresolved / not yet testable. This vocabulary aligns to the design-system-ASK Evidence State profile by reference (UO owns assignment; DS owns the role vocabulary/value-mapping/presentation contract); the explicit role mapping — including that contradicted is consumer-local, outside the current DS profile — is in methodology.md §Living Implementation Consistency matrix.
3. Finding-level composite treatment. When the row assessments within a finding diverge — including across the temporally distinct surfaces noted in methodology.md — the finding-level reading is composite. The composite is explained in the finding's interpretation prose rather than forced into a single controlled value.

Prototype source contact has surfaced cases where a single direction value cannot capture the implementation condition cleanly — partial support and partial weakening can coexist within one finding, and surface-specific readings can diverge across inventory snapshot, entitlement event, rolling advancement, and completion. The row-level vocabulary has held across operator-side scratch extractions but is not yet expert-reviewed; the finding-level composite treatment is held as prose, not as schema, and no controlled enum is committed for it. Final controlled vocabularies remain deferred to later prototype work.

A downstream, non-prescriptive option that could plausibly change the trajectory of a weakened or contradicted assumption. Candidates are surfaced, not endorsed. They are plural and actor-typed where possible. They are not recommendations.