---
title: validation
framework: Create ML
role: symbol
role_heading: Instance Property
platforms: [macOS 14.0+]
path: createml/mlactivityclassifier/modelparameters-swift.struct/validation-swift.property
---

# validation

The validation data source.

## Declaration

```swift
var validation: MLActivityClassifier.ModelParameters.Validation { get set }
```

## Discussion

Discussion If you don’t specify validation data, the training process automatically sets aside a random subset of the training data as the validation data.

## See Also

### Accessing the training parameters

- [validationData](createml/mlactivityclassifier/modelparameters-swift.struct/validationdata.md)
- [batchSize](createml/mlactivityclassifier/modelparameters-swift.struct/batchsize.md)
- [maximumIterations](createml/mlactivityclassifier/modelparameters-swift.struct/maximumiterations.md)
- [predictionWindowSize](createml/mlactivityclassifier/modelparameters-swift.struct/predictionwindowsize.md)