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

# L0 · Source & Authority Registry

> The first layer. Classifies every input before anything else can touch it.

export const Source = () => <Tooltip tip="Anything that comes into the system as input: rules, drawings, datasheets, prior vessel records. Locked once ingested.">source</Tooltip>;

<Note>
  **In plain terms:** Before any document is used, L0 decides who issued it, how much
  authority it carries, what version it is, which yard owns it, and who is allowed to
  see it. Nothing gets used until it passes through here.
</Note>

## What it does

L0 defines the trust, authority, version, access rights, and ownership of every
<Source /> before it enters the system. An ABS Rules PDF, a USCG section, a yard's
internal standard, a prior vessel's drawing package, a vendor datasheet, and a
research dataset all enter here and get tagged first.

This is the first layer because rule authority, version, ownership, and licensing
determine what the system is allowed to trust, cite, retrieve, and export.

## Source roles

| Source type                      | Role                                | How Forge handles it                                                                |
| -------------------------------- | ----------------------------------- | ----------------------------------------------------------------------------------- |
| ABS Rules and Guides             | Authority-bearing engineering rules | Used as structured rules, not generic PDFs; rule version and effective date tracked |
| USCG CFR                         | Regulatory requirements             | Applied with filters for vessel type, service, flag, tonnage, and operating context |
| Prior vessel records             | Evidence (precedent)                | Available for retrieval but never sufficient on their own to authorize a decision   |
| Research datasets, vendor papers | Reference                           | Useful for context, never sufficient for a decision                                 |

## What L0 outputs

Every source leaves L0 tagged with:

* `source_id`
* `authority_level` (authority / evidence / reference)
* `rule_version_id`
* `tenant_id` (which yard owns it)
* `doc_type`, `market_sector`, `topic`
* `access_policy`

## Why it is first

If you do not know what a document is and how much it can be trusted *before* you
reason over it, every downstream conclusion is suspect. L0 makes trust an explicit,
recorded property of every input, which is what lets later layers cite sources with
confidence.

Related: [Sources vs. Decisions](/concepts/sources-vs-decisions).