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

# ConnectionValueTypeUnexisting validation rule

> Validates that all connection value types defined in the data model exist. Ensures the data model can be deployed to CDF.

This rule checks that all connection value types defined in the data model exist.

## Why it matters

If a connection value type does not exist, the data model cannot be deployed to CDF.
This means that the connection cannot function.

## Example

If the `WindTurbine` view has a connection property `windFarm` with value type `WindFarm`, but the `WindFarm` view is not defined,
the data model cannot be deployed to CDF.

## Further reading

* [Validation rules](/cdf/deploy/neat/validation/index)