A method of creating computer instructions for transforming inbound instances, being instances of an inbound data format, into outbound instances, being instances of an outbound data format. At least one of the inbound and outbound data formats has a number of segments arranged in a hierarchical manner. 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 inbound data format on the display device and allowing the developer to use the input device to create a graphical representation of the outbound data format on the display device.