> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cast.digitalfinancehq.com/llms.txt
> Use this file to discover all available pages before exploring further.

# The five primitives

> Everything else is a projection of these five objects.

CAST is built on five canonical objects. Everything an operator, an auditor, or an agent sees is a projection of these five. They do not change between verticals — only the event types, policy rules, and work-order structures do.

<CardGroup cols={2}>
  <Card title="Event" icon="bolt" href="/primitives/event">
    An immutable record of something that happened. The only source of truth.
  </Card>

  <Card title="Policy Version" icon="scroll" href="/primitives/policy-version">
    A versioned, immutable rule set, pinned to every event at processing time.
  </Card>

  <Card title="Work Order" icon="clipboard-list" href="/primitives/work-order">
    The container holding the full context and decisions for a payment.
  </Card>

  <Card title="Posting" icon="book" href="/primitives/posting">
    A journal-ready ledger entry, created only after mutual authorization.
  </Card>

  <Card title="Case" icon="triangle-exclamation" href="/primitives/case">
    A governed exception — dispute, non-response, breach, or gap.
  </Card>
</CardGroup>

## And one property: lineage

<Note>
  **Lineage is not a sixth object.** It is the immutable hash chain that binds every posting back through the events, decisions, and policy version that produced it. It is rendered throughout CAST as `lineage()` — a function over the five objects, not a thing beside them.
</Note>

<Card title="Lineage — the proof is the asset" icon="link" href="/primitives/lineage">
  How the hash chain makes a transaction insurable, financeable, and survivable.
</Card>

## The model at a glance

```text theme={"dark"}
Event ──▶ Policy Version ──▶ Work Order ──▶ Posting
                                  │
                                  └──▶ Case (on exception)

lineage() binds every step back to the originating Event.
```

Append-only by design. Mutual authorization is enforced before any high-risk posting. This produces verifiable proof without added complexity.