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ADR 0005: Source Evidence Is Owned by Source Documents

Context

BooksPlus 3 needs durable evidence for accounting activity. Evidence may support journal entries, purchases, sales, inventory events, close work, reports, approvals, and future workflows.

If each workflow invents its own evidence model, the product will lose consistent source identity, supersession behavior, auditability, and review paths.

Accounting needs to consume evidence facts, but accounting posting should not own file storage, evidence identity, or capture history.

Decision

BooksPlus 3 will treat source evidence as owned by the Source Documents domain area.

SourceDocument and related evidence references are the canonical foundation for evidence identity and linkage. Evidence must remain generic enough to support multiple business objects over time, not only journal entries.

The evidence subsystem follows these rules:

  • Evidence identity belongs to Source Documents.
  • Accounting may require and consume evidence facts, but does not own evidence identity or storage.
  • Evidence should not be silently overwritten.
  • Later evidence may supersede earlier evidence while preserving prior identity and history.
  • Original documents or durable source artifacts are preferred when available.
  • Automated or credential-backed retrieval is a later controlled capability, not the baseline model.
  • Security-sensitive secrets must not be stored as ordinary application record data.
  • Consequential evidence actions should be auditable.

Rationale

A shared evidence model lets BooksPlus preserve traceability across workflows without duplicating document logic inside each accounting area.

This keeps posting focused on accounting enforcement while Source Documents owns source identity, evidence references, supersession, and capture metadata.

Consequences

Positive consequences:

  • BooksPlus has one canonical evidence foundation.
  • Evidence can support journal entries, close, purchases, sales, inventory, reports, and future workflows.
  • Supersession and audit behavior can be consistent.
  • Advanced capture modes can be added later without replacing the basic evidence model.

Negative consequences:

  • Feature workflows must map their evidence needs into Source Documents.
  • Advanced automation must wait for security, authorization, and audit controls.
  • Evidence storage and company-data backup rules need explicit design.

Implementation guidance

  • Use SourceDocument and evidence references as the canonical evidence objects.
  • Do not introduce workflow-specific parallel evidence identity models.
  • Generalize linkage by business object type and identifier.
  • Preserve artifact identity, hash or verification data where appropriate, and supersession history.
  • Keep evidence-review requirements as policy facts consumed by posting, close, or review workflows.
  • If credential-backed capture is added later, store secret references separately and audit privileged retrieval.
  • ../../accounting/source-documents.md
  • ../../contracts/source-document.contract.md
  • ../../contracts/kernel.contract.md
  • 0014-append-only-security-audit-events.md