1. A computer-implemented method for maintaining consistency of a data structure, the method comprising: retrieving, at a computing device, the data structure from computer-readable memory, the data structure comprising a model including a plurality of objects and references between objects; receiving, at the computing device, first user input indicating a set of first changes to the model, each change in the set of first changes comprising one or more primitive operations, each primitive operation being executable to modify the model; applying changes of the set of first changes to the model to provide a first modified model; receiving, at the computing device, second user input indicating a set of second changes to the model, each change in the set of second changes comprising one or more primitive operations, each primitive operation being executable to modify the model; comparing the set of first changes to the set of second changes to identify a conflicting operation; applying one or more inverse operations to the first modified model to provide a second modified model, the one or more inverse operations corresponding to the conflicting operation and to one or more changes occurring after the conflicting operation; removing the conflicting operation from the set of first changes; defining a subset of first changes, the subset of first changes comprising the one or more changes occurring after the conflicting operation; reconciling one or more changes in the subset of first changes based on removal of the conflicting operation to provide a reconciled subset of first changes; defining an updated model by applying changes of the reconciled subset of first changes to the second modified model; and storing the updated model in computer-readable memory.