1. A device for causing a manipulation performed on an object as an image of a mapping of at least a part of graph data including nodes and edges to be reflected in the graph data, the device comprising: means for accessing a graph repository storing the graph data; means for specifying, from among nodes in the graph data that are related to the object being modified by the manipulation, a shared node that may be related to another object as well; and means for reflecting the manipulation in the graph data while preventing the shared node from being modified.