1. A system for maintaining data integrity during editing of multi-dimensional data, comprising: a planning data repository system containing multi-dimensional data having complex relationships; a calculation engine associated with the planning data repository for implementing data integrity in response to a request, the calculation engine including: an optimizing module for optimizing a back-solving based on a parent/child table giving relationships and dependencies between one or more target cells and other cells in a sub-cube of the multi-dimensional data, and a back-solving module for implementing the back-solving in response to a change request for a cell in the sub-cube, including a module for setting a value of a specific cell in the sub-cube based on the optimization to meet a requirement in the change request.