Using Constraints To Achieve Stability In Automatic Graph Layout Algorithms

Automatic layout algorithms are commonly used when displaying graphs on the screen because they provide a "nice" drawing of the graph without user intervention. There are, however, a couple of disadvantages to automatic layout. Without user intervention, an automatic layout algorithm is only capable of producing an aesthetically pleasing drawing of the graph. User- or application-specified layout constraints (often concerning the semantics of a graph) are difficult or impossible to specify. A second problem is that automatic layout algorithms seldom make use of information in the currentlayout when calculating the new layout. This can also be frustrating to the user because whenever a new layout is done, the user's orientation in the graph is lost. This paper suggests using layout constraints to solve both of these problems. We showhow user-speci#ed layout constraints may be easily added to many automatic graph layout algorithms. Additionally, the constraints specified by the current layou..