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

> ## Agent Instructions
> To act on Atlan objects, use the Atlan MCP server at https://api.atlan.com/mcp or the SDK. To install or publish skills from a terminal, use the `aireg` CLI; `aireg --map json` prints its command map. The `atlanai` CLI is deprecated. Run a read-only identity check before any write.
> The docs MCP server at /mcp searches these docs only. It cannot read or change Atlan objects.
> SDK packages: Python `atlanai` (PyPI) and TypeScript `@atlanai/sdk` (npm). Show Python first, then TypeScript.
> These docs cover Atlan AI Registry, Atlan's hosted product. The AI registry specification and aireg CLI are maintained separately. /open-source lists publicly reachable signed installers and explains that the source repository and hosted CLI reference currently require GitHub access. Do not claim the repository or its reference docs are publicly accessible. Use these docs for Atlan-specific setup such as the adapter, sign-in and workspaces.

# Ontology

> Give agents one shared model of your business, so they know what a customer or an order is before they query your data.

<Badge color="orange">Preview</Badge>

Ontology is one shared model of your business that agents read before they query your data. Data and platform teams define customers, orders, and their relationships so agents share the same meaning.

You describe the model once, publish it as a fixed release, and map it to your warehouse tables. Agents then ask for just the part of the model a task needs.

```mermaid theme={null}
flowchart TD
  O["Ontology and binding releases<br/>definitions and table mappings"]
  A["Your agent"]
  W[("Your warehouse")]
  O -- "context through MCP" --> A
  A -- "query with its own connection" --> W
```

The running example on these pages is a retail company. Its model has four object types (Customer, Order, Product, Store) and two links: a Customer places an Order, and an Order contains Products.

## How it works

Logical definitions follow five steps. The context tools read published releases.

| Step | What happens | Where |
| - | - | - |
| 1. Draft | Add object types, properties and links as drafts. Context retrieval excludes drafts. | Studio **Definitions** |
| 2. Validate | Studio checks all drafts together and lists errors and warnings. | Studio **Publish** |
| 3. Release | Publish a semantic version such as `1.0.0`. A release never changes. | Studio **Publish** |
| 4. Bind | Map the release's types, properties and links to tables, columns and joins. | Studio **Data bindings** |
| 5. Agent context | Agents fetch a small, ranked slice of one exact release, with the mapped table names. | MCP tools, Studio **Agent context** |

## What you can do

<CardGroup cols={2}>
  <Card title="Model your business" icon="diagram-project" href="/ontology/tutorials/first-ontology">
    Add types and links, then publish your first release.
  </Card>

  <Card title="Map the model to tables" icon="table" href="/ontology/concepts/bindings">
    Tell agents which tables, columns and joins hold each type.
  </Card>

  <Card title="Give agents bounded context" icon="robot" href="/ontology/how-tos/use-with-agents">
    Agents fetch only the definitions a question needs.
  </Card>

  <Card title="Govern policy records" icon="scale-balanced" href="/ontology/how-tos/manage-records">
    Keep policies and controls with effective dates.
  </Card>

  <Card title="Review drafts from agents" icon="user-check" href="/ontology/how-tos/review-agent-drafts">
    Agents propose definitions; a person approves the save.
  </Card>

  <Card title="Automate with the API" icon="code" href="/cookbooks/how-tos/ontology">
    Import, validate and publish releases from scripts.
  </Card>
</CardGroup>

## Get started

<Card title="Build your first ontology" icon="rocket" href="/ontology/tutorials/first-ontology">
  Publish a retail model and inspect its agent context in 15 minutes.
</Card>

## Key concepts

* **[Object type](/ontology/concepts#object-type)**: a kind of business thing, such as Customer, with its properties.
* **[Link type](/ontology/concepts#link-type)**: a named relationship between two types, such as Customer *places* Order.
* **[Release](/ontology/concepts#release)**: a published, unchangeable snapshot of the model that agents read.
* **[Bindings](/ontology/concepts/bindings)**: a published mapping from one release to tables, columns and joins.
* **[Knowledge record](/ontology/concepts#record)**: a policy or control stored with the dates it is in force.

## Studio or API

Ontology Studio and the API share the same release rules, so you can start in one and continue in the other.

| Task | In Studio | Through the API |
| - | - | - |
| Create an ontology | **New ontology** | Create it in Studio first |
| Add definitions | Form or JSON editor, or **Import file** | `POST /ontology/v1/imports/preview`, then `/imports/apply` |
| Validate and publish | **Publish** page | `POST /ontology/v1/validations`, then `/releases` |
| Map to data | **Data bindings** | `POST /ontology_binding/v1/validations`, then `/releases` |
| Read context | **Agent context** | MCP tools, or `POST /ontology/v1/context-queries` |

## Common tasks

| I want to… | Go to |
| - | - |
| Learn the terms before I start | [Ontology concepts](/ontology/concepts) |
| Build a model step by step | [Build your first ontology](/ontology/tutorials/first-ontology) |
| Tell agents where each type lives in the warehouse | [Bindings](/ontology/concepts/bindings) |
| Connect an agent and choose the right tool | [Use Ontology with agents](/ontology/how-tos/use-with-agents) |
| Store policies with effective dates | [Manage knowledge records](/ontology/how-tos/manage-records) |
| Approve definitions an agent drafted | [Review agent-drafted definitions](/ontology/how-tos/review-agent-drafts) |
| Publish from a script or CI job | [Publish an ontology through the API](/cookbooks/how-tos/ontology) |
| Look up a field or limit | [Ontology data model](/ontology/references/data-model) |

## Availability and limits

* **Preview, opt-in app.** An administrator installs the **Ontology** app; it is not part of default onboarding. Bindings need the **Ontology Binding** app too. See [Install and manage apps](/registry/apps/how-tos/install-apps).
* **No data copy.** Ontology stores definitions and a small set of governed policy records. Customer, order and other warehouse rows stay in your warehouse.
* **No SQL runs.** Neither Ontology nor bindings connect to a source, generate SQL or run a query. Agents query with their own connection.
* **Actions are described, not run.** An action type records what an operation needs and changes. Nothing executes it.
* **Release size.** One release holds up to 256 definitions.

## Reference

* [Ontology data model](/ontology/references/data-model): every definition kind, field and limit.
* [All MCP tools](/tools/mcp/references/tool-catalog): the six Ontology tools agents call.
* [Public API](/api/references/api-reference): the `/ontology/v1` and `/ontology_binding/v1` operations.

## Troubleshooting

See [Ontology errors](/cookbooks/troubleshooting/ontology) for import, validation, publication and context errors.


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