We describe a package of practical tools and libraries for manipulating graphs and their drawings. Our design, which aimed at facilitating the combination of the package components with other tools, includes stream and event interfaces for graph operations, high-quality static and dynamic layout algorithms, and the ability to handle sizable graphs. We conclude with a description of the applications of this package to a variety of software engineering tools.

Hierarchical graphs and clustered graphs are useful non-classical graph models for structured relational information. Hierarchical graphs are graphs with layering structures; clustered graphs are graphs with recursive clustering structures. Both have applications in CASE tools, software visualization, and VLSI design. Drawing algorithms for hierarchical graphs have been well investigated. However, the problem of straight-line representation has not been solved completely. In this paper, we answer the question: does every planar hierarchical graph admit a planar straight-line hierarchical drawing? We present an algorithm that constructs such drawings in linear time. Also, we answer a basic question for clustered graphs, that is, does every planar clustered graph admit a planar straight-line drawing with clusters drawn as convex polygons? We provide a method for such drawings based on our algorithm for hierarchical graphs.

. Generating incrementally stable layouts is important for visualizing dynamic graphs in many applications. This paper describes DynaDAG, a new heuristic for incremental layout of directed acyclic graphs drawn as hierarchies, and its application in the DynaGraph system. 1 Introduction Effective techniques have been developed for some important families of graph layouts, such as hierarchies, planar embeddings, orthogonal grids and forced-directed (spring) models [1]. These techniques have been incorporated in practical user interfaces that display static diagrams of relationships between objects [19, 18, 17]. Static diagrams are not completely satisfactory because in many situations, the displayed graphs can change. Three common scenarios are: Manual editing. Most interactive graph drawing systems allow users to manually insert and delete nodes and edges. Layouts must be updated dynamically to reflect such changes. Browsing large graphs. When only static layout is available, browsin...

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We have a project currently underway that attempts to use 3D workstations to provide insight into programs, their structure and their execution, through the use of a variety of user-definable displays. We offer a variety of different presentation styles and utilize a variety of different layout methods and heuristics. This paper describes the underlying engine that we have developed to support this range of presentations.

and Demo) Michael Himsolt Universitat Passau, 94032 Passau, GERMANY himsolt@fmi.uni-passau.de Abstract. GraphEd is an extensible graph editor. Its powerful object oriented user interface supports all operations that are necessary for the convenient construction and manipulation of graphs. Graph grammars can be used as a macro system to create structured graphs. GraphEd's modular structure and the application interface support the easy integration of algorithm modules which are written in C, or can run external programs. The user may construct graphs interactively, select algorithms from a menu, and view the results of an algorithm directly on screen. Several graph layout algorithms assist the user to tidy graph drawings, and help the programmer to visualize results or debug complex algorithms. Actual applications range from standard graph algorithms over graph drawing algorithms, algorithm animation and combinatorial algorithms to front ends for circuit design systems. 1 Introduction...

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...

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this paper we propose a set of layout operations ensuring exible and convenient interactive editing of GRADE's CD and ER diagrams. The set of our operations includes several procedures oriented on processing of intermediate stages of layouts when incremental design of diagrams prevails. We have also integrated in a single system tools for both, fully automatic layout, and for only direct painting of graphic primitives. In this way we have lled to some extent the gap between the simple painting of separate diagram objects and the fully automatic drawing of entire diagram.

this article we describe the concepts we used for implementing an experimental system which controls the computer screen contents and its layout. We give two examples of different standard applications into which we included ADL successfully, namely hypertext for a window layout problem and graph-browser for a hierarchical graph layout problem within a particular window. The results show that automatic (and tool independent) display layout will be possible in the near future even in an interactive environment