# LibTmux.Query.ToOptional

- **Package:** libtmux-haskell
- **Language:** Haskell
- **Kind:** data type
- **Source:** https://github.com/libtmux/libtmux-haskell/blob/663e212622a02aa74a9bdc8ff71e2b45fcb1d4d5/internal/LibTmux/Internal/Query.hs#L75
- **Page:** https://libtmux.org/en/haskell/latest/reference/libtmux-query-t-tooptional/

```haskell
data ToOptional parent child
```

An observed optional relationship, used with [`optionalRelated`](/en/haskell/latest/reference/libtmux-query-v-optionalrelated/).
 Known absence is separate from an unavailable relationship.