5. A data processing system comprising a processor and accessible memory, the data processing system particularly configured to perform the steps of: loading a first language definition and a second language definition; loading a transformation definition corresponding to the first language definition and the second language definition, wherein the transformation definition maps a first construct of the first language definition to a second construct of the second language definition; loading a validation rule definition, wherein the validation rule definition defines a successful transformation between the first construct and the second construct and indicates whether the transformation definition produces a valid transformation between the first construct and the second construct; and applying the validation rule definition to the transformation definition to produce a validation result indicating whether the transformation definition produces a valid transformation between the first language definition and the second language definition; and storing the validation result.
5. A data processing system comprising a processor and accessible memory, the data processing system particularly configured to perform the steps of: loading a first language definition and a second language definition; loading a transformation definition corresponding to the first language definition and the second language definition, wherein the transformation definition maps a first construct of the first language definition to a second construct of the second language definition; loading a validation rule definition, wherein the validation rule definition defines a successful transformation between the first construct and the second construct and indicates whether the transformation definition produces a valid transformation between the first construct and the second construct; and applying the validation rule definition to the transformation definition to produce a validation result indicating whether the transformation definition produces a valid transformation between the first language definition and the second language definition; and storing the validation result. 8. The data processing system of claim 5 , wherein the transformation definition is an extensible stylesheet language file specifying an extensible stylesheet language transformation.