---
id: ADR-PFM-ELG-003
title: Answers are three-valued and each use decides uncertainty
product_area: platform
module: eligibility
revision: 1
status: proposed
design_intent: confirmed
source_sha:
  services-platform: ad3f6a6582843008ed0f5a17b131878d15829af1
  react-console: baf6dae382d6f41dce976c7f848667ccc37e076f
decision: >-
  Return eligible, ineligible or indeterminate, then apply the uncertainty
  policy chosen for that use.
constrains:
  - DOM-PFM-ELG-002
  - DOM-PFM-ELG-003
  - SVC-PFM-ELG-eligibility
  - WF-PFM-ELG-004
origin: >-
  Eligibility Engine architecture D-08 (three states with Kleene composition,
  consumer-declared fail policy), approved by Andrew 2026-10-17 (PLAT-M11
  "Decisions"); PLAT-M11 plan D1 "Always check" (2026-10-21)
alternatives:
  - option: Collapse uncertainty into false
    why_not: A missing record or outage would become an unexplained refusal.
  - option: Put the uncertainty policy on the rule
    why_not: Different uses of the same rule can require different risk policies.
consequences:
  - Unavailable evidence produces reasons for uncertainty.
  - Purposes provide default policies that individual uses can override.
  - Closed uncertainty can use the rule’s member-facing message.
supersedes: []
evidence:
  - >-
    services-platform at ad3f6a6:
    docs/proposals/eligibility/17-decision-register.md;
    docs/milestones/PLAT-M11-eligibility-rules.md (Decisions)
  - >-
    services-platform at ad3f6a6: services/evaluate/policy.ts;
    docs/eligibility.md §9.1
---
# Answers are three-valued and each use decides uncertainty

## Context

An unavailable fact differs from a fact that disproves qualification.

## Decision

Return eligible, ineligible or indeterminate, then apply the uncertainty policy chosen for that use.

## Alternatives Considered

Collapse uncertainty into false: A missing record or outage would become an unexplained refusal.

Put the uncertainty policy on the rule: Different uses of the same rule can require different risk policies.

## Consequences

Unavailable evidence produces reasons for uncertainty. Purposes provide default policies that individual uses can override. Closed uncertainty can use the rule’s member-facing message.