A method of generating computer instructions for creating instances of a hierarchical data format from a flat record stream, the flat record stream containing data in a flat format and containing at least some data redundancy. The method uses a computing device having at least a processor, a memory, a display device and an input device. The method includes allowing a developer to use the input device to create a graphical representation of the hierarchical data format, and allowing a developer to use the input device to create a graphical representation of a mapping between the flat format and the hierarchical format. The method further includes generating, at the processor, computer instructions which when executed on a computer cause the computer to create from the flat record stream instances of the hierarchical format, wherein the instances of the hierarchical format remove the data redundancy.