> For the complete documentation index, see [llms.txt](https://docs.opendatadiscovery.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.opendatadiscovery.org/developer-guides/api-reference/relationships.md).

# Relationships

`RelationshipController` exposes three endpoints. The same payloads are surfaced on the source and target dataset's detail pages — when a dataset participates in any relationships, those are listed under the dataset's relationships cluster. For the cardinality model (`ONE_TO_EXACTLY_ONE` / `ONE_TO_ZERO_OR_ONE` / `ONE_TO_ONE_OR_MORE` / `ONE_TO_ZERO_ONE_OR_MORE`), the per-adapter ingestion coverage, and the ERD vs graph relationship distinction, see the [Relationships](/features/data-modelling/relationships.md) page.

| Method + Path                                                         | Operation                  | What                                                                                                                                                                                                                          |
| --------------------------------------------------------------------- | -------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `GET /api/relationships?page=N&size=M&type=ERD\|GRAPH\|ALL&query=...` | `getRelationships`         | Paginated list with optional type filter and free-text query. The `query` matches the relationship's own name (case-insensitive substring) — **not** the source or target dataset name. Returns `DataEntityRelationshipList`. |
| `GET /api/relationships/erd/{relationship_id}`                        | `getERDRelationshipById`   | Full ERD relationship details (source / target / cardinality / owner).                                                                                                                                                        |
| `GET /api/relationships/graph/{relationship_id}`                      | `getGraphRelationshipById` | Full graph relationship details (source / target node, edge metadata).                                                                                                                                                        |

{% hint style="warning" %}
**The `{relationship_id}` path parameter is the relationships-class data entity id, not the row id of the relationship itself** — supplying the relationship's own primary key returns **HTTP 404**. Always round-trip through the `id` returned by `GET /api/relationships`, which is the value both detail endpoints expect. The full explanation is on the [Relationships feature page → Known operator caveats](/features/data-modelling/relationships.md#known-operator-caveats).
{% endhint %}

{% hint style="warning" %}
**The list endpoint carries no per-resource permission — any authenticated caller enumerates every visible relationship.** As of 0.28.0 it applies the catalog's default visibility rules (soft-deleted, hollow, and excluded-from-search relationship entities are hidden, matching `GET /api/dataentities`); on 0.27.x and earlier it was a full enumeration of the relationship class with no visibility filtering at all. It still does not filter by owner, namespace, or tenant — do not treat it as an access-filtered surface. See the [Relationships feature page → Known operator caveats](/features/data-modelling/relationships.md#known-operator-caveats) for the visibility and authorization detail.
{% endhint %}

## See also

* [API Reference hub](/developer-guides/api-reference.md) — the full per-feature index.
* [Relationships](/features/data-modelling/relationships.md) — feature description, cardinality model, per-adapter ingestion coverage, ERD vs graph distinction.