> ## Documentation Index
> Fetch the complete documentation index at: https://base-a060aa97-docs-add-b20-spec.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# IPolicyRegistry.compositePolicyChildIds

> Generated B20 reference for compositePolicyChildIds(uint64).

[Related concept](/base-chain/specs/upgrades/beryl/b20/specification/concepts/policies-and-scopes)

## Signature

```solidity theme={null}
function compositePolicyChildIds(uint64 policyId) external view returns (uint64[] memory);
```

| Field               | Value                             |
| ------------------- | --------------------------------- |
| Selector            | `0x7c40df74`                      |
| Canonical signature | `compositePolicyChildIds(uint64)` |

## Description

Returns the child-policy set of the composite `policyId`.
Dev: Child-policies are listed in the order they were last written.
Dev: Returns an empty array for simple policies, built-in sentinels, unknown IDs, and
malformed IDs. Never reverts.
Dev: An empty return unambiguously means "not a composite".
Dev: The registry preserves the caller's ordering verbatim and neither sorts nor
de-duplicates.
Param: policyId Policy to query.
Return: Child policy IDs, or an empty array.

## Access control

Read-only or ERC-20-standard access rules unless the NatSpec states otherwise.

## Policy interaction

This is part of the singleton PolicyRegistry surface used by B20 policy scopes.

## Example

```solidity theme={null}
IPolicyRegistry(target).compositePolicyChildIds(arg0);
```

## Related

* [IPolicyRegistry reference](/base-chain/specs/upgrades/beryl/b20/specification/reference/interfaces/IPolicyRegistry)
* [Constants & addresses](/base-chain/specs/upgrades/beryl/b20/specification/reference/constants-and-addresses)