An incremental approach to aesthetic graph layout

In CASE tools, software representations-dataflow diagrams and entity-relationship diagrams, for example-change or are changed interactively during software evolution. The displays of these representations should only change minimally so that the user can follow and validate the process. This can be achieved by having a layout approach that respects the current node positioning and draws new edges without disturbing any of the existing nodes or edges. New nodes may not overlap existing nodes and only cause any overlapped edges to be redrawn. This incremental graph layout problem is addressed here. A practical algorithm and its implementation, which efficiently routes edges according to the criteria of no node overlap and (heuristically) minimum crossings, bends, and length of edges, are discussed.