Some restrictions exist regarding the Attributes of a VariableType or a Variable used as an InstanceDeclaration with regard to the data type of the Value Attribute.

When a Variable used as InstanceDeclaration or a VariableType is overridden or instantiated the following rules apply:

1. The DataType Attribute can only be changed to a new DataType if the new DataType is a subtype of the DataType originally used.
2. The ValueRank Attribute may only be further restricted
3. ‘Any’ may be set to any other value;
4. ‘ScalarOrOneDimension’ may be set to ‘Scalar’ or ‘OneDimension’;
5. ‘OneOrMoreDimensions’ may be set to a concrete number of dimensions (value > 0).
6. All other values of this Attribute shall not be changed.
7. The ArrayDimensions Attribute may be added if it was not provided or when modifying the value of an entry in the array from 0 to a different value. All other values in the array shall remain the same.