private static boolean areStructFields(Field currentField, Field nextField) {
        return (currentField.getDataType() instanceof StructDataType) &&
                (nextField.getDataType() instanceof StructDataType);
    }
Validates the changes between a current and next document type used in a document database.

@author toregge
config-model/src/main/java/com/yahoo/vespa/model/application/validation/change/search/DocumentTypeChangeValidator.java