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

# Field paths and dependencies

> Address nested state and model dependency edges in the DAH-backed runtime.

All state operations use string paths. Dots describe nested objects and array positions:

```text theme={null}
registrant.name
event.schedule
guests.0.email
guests.0.invitation.send_at
```

## Parent hierarchy

`set_field("guests.0.email", value)` ensures intermediate nodes such as `guests` and `guests.0` exist. It also adds parent-to-child dependency edges for each path segment.

```python theme={null}
from core.state.canonical.state import CanonicalState

state = CanonicalState()
state.set_field("guests.0.email", "grace@example.com")

assert set(state.get_children("guests")) == {"guests.0"}
assert set(state.get_children("guests.0")) == {"guests.0.email"}
```

The ordering of returned child paths is not documented; compare sets if order does not matter to your application.

## Explicit dependencies

Use `add_field_dependency()` for an additional single-source dependency:

```python theme={null}
state.set_field("registrant.email", "ada@example.com")
state.add_field_dependency("registrant.email", "status")

assert "status" in state.get_children("registrant.email")
```

The underlying directed acyclic hypergraph also supports multi-source hyperedges. That structure is exposed through `get_dah()` and is currently an internal-oriented API; see [DAH-backed storage](/architecture/dah-storage) before depending on it directly.

## Node identity

Paths are the public lookup keys. Each node also receives a UUID, available through `get_field_uuid(path)`. UUIDs are useful for graph identity but should not replace paths in user-facing or persisted contracts unless your application explicitly manages that mapping.