1. A computer-implemented method for transforming data, the method comprising: providing a transformation directive in a business object data type definition statement, the transformation directive specifying one or more transformations to be applied to data to convert the data into a format which conforms to predetermined restrictions before the data is stored in a variable of the business object data type being defined; interpreting the at least one transformation directive by a runtime framework; applying the transformation to data which is assigned to a variable of the business object data type that was defined; checking the transformed data to determine if the transformed data conforms to the predetermined restrictions; and storing the transformed data in the variable.