53. A computer readable medium storing a computer program which when executed by at least one processor transforms an input hierarchical data structure to an output hierarchical data structure at a transformation engine, the computer program comprising sets of instructions for: at the transformation engine, receiving the input hierarchical data structure, said input hierarchical data structure comprising input data sets, each input data set comprising at least one key value pair, wherein a key value pair includes a key and an associated value for the key; at the transformation engine, transforming said input data sets in the input hierarchical data structure to output data sets in the output hierarchical data structure based on a particular transformation template, wherein the set of instructions for transforming said input data sets to the output data sets comprises a set of instructions for using said particular transformation template: (i) to identify input data sets of the input hierarchical data structure to transform; and (ii) to modify content of the identified input data sets differently by: modifying a key associated with a particular key value pair in an identified input data set when said particular transformation template specifies a modified key for said particular key value pair; modifying a value associated with a particular key value pair in an identified input data set when said particular transformation template specifies a modified value for said particular key value pair; and modifying a key and a value associated with a particular key value pair in an identified input data set when said particular transformation template specifies a modified key and a modified value for said particular key value pair; and storing said output data structure.
54. The computer readable medium of claim 53 , wherein the set of instructions for transforming said input data sets to the output data sets further comprises a set of instructions for using said particular transformation template to specify an output process defining a mapping function for converting a key in the input hierarchical data structure into a different key in the output hierarchical data structure.