1. In a data visualisation configuration system, a method of creating one or more modifiable data interface objects that are used to represent data values for visualization in a graphical representation, the method comprising the steps of: detecting an instruction to create a new modifiable data interface object from a list of parent modifiable data interface objects, creating a proxy modifiable data interface object as the new modifiable data interface object for each parent modifiable data interface object associated with the instruction, and enabling the proxy modifiable data interface object to be available for modification, where the proxy modifiable data interface object refers to its associated parent modifiable data interface object.