ModelMap<Item> getChildren()
}

class PluginRules extends RuleSource {
    @Defaults void setDefaultFileSize(@Each FileItem file) {
        file.size = 1024
    }

    @Rules void applyValidateRules(ValidateRules rules, @Each DirectoryItem directory)  {}
}
apply plugin: PluginRules

abstract class ValidateRules extends RuleSource {
    @Validate
    void validateSizeIsPositive(ModelMap<FileItem> files) {