Algorithms and Bounds for Drawing Directed Graphs

In this paper we present a new approach to visualize directed graphs and their hierarchies that completely departs from the classical four-phase framework of Sugiyama and computes readable hierarchical visualizations that contain the complete reachability information of a graph. Additionally, our approach has the advantage that only the necessary edges are drawn in the drawing, thus reducing the visual complexity of the resulting drawing. Furthermore, most problems involved in our framework require only polynomial time. Our framework offers a suite of solutions depending upon the requirements, and it consists of only two steps: (a) the cycle removal step (if the graph contains cycles) and (b) the channel decomposition and hierarchical drawing step. Our framework does not introduce any dummy vertices and it keeps the vertices of a channel vertically aligned. The time complexity of the main drawing algorithms of our framework is $O(kn)$, where $k$ is the number of channels, typically much smaller than $n$ (the number of vertices).Comment: Appears in the Proceedings of the 26th International Symposium on Graph Drawing and Network Visualization (GD 2018

The Graphlet System (System Demonstration)

. Graphlet is a portable, object oriented toolkit for graph editors and graph drawing algorithms, and is the successor of the GraphEd system. Graphlet is based on LEDA and Tcl/Tk. Algorithms can be implemented in C++ and LedaScript, a new scripting language based on Tcl/Tk. The GML format is a portable file format for graphs. The implementation and visualization of graph algorithms is an important area in research and applications. There is a growing number of systems to support this process. LEDA [8] and GraphBase [7] concentrate on the implementation of a library of graph algorithms. Systems like daVinci [4], DynaDAG [11], D-ABDUCTOR [14] and EDGE [10] concentrate on graph visualization and/or graph editing, while CABRI [3], GD-Workbench [2], GraphEd [6], the Graph Editor Toolkit [9] or VCG [13] combine an editor and a library of algorithms. The scope of these systems ranges from small and on-purpose systems to large, complex ones. However, the user interfaces of many systems are not..

Implementing Graph Algorithms with GraphEd (Extended Abstract)

We present an overview of the application interface of GraphEd, an extensible graph editor system. GraphEd's algorithms are written in C and use the Sgraph data structure. The user may construct graphs interactively and select the algorithms from a menu. GraphEd communicates with other programs via a simple, yet sophisticated file format. Already implemented applications range from standard graph algorithms over graph drawing algorithms, combinatorial algorithms up to front ends for circuit design systems

An Interchange File Format for Graphs

This paper describes a interchangable file format for storing graphs in a file, as it is used by the GraphEd system. This format combines an adjacency list with embedded graphical information. It is designed as an extendible format and provides facilities such that other programs can easily add their own information in their own format. 1 Introduction With the devopment of several graph editors and graph manipulation packages, such as GraphEd [2, 3], EDGE [7], VEGA, vcg [6], gem, dot, graphbase [5], or daVinci [1], several formats for storing graphs have been implemented. However, nearly each tool uses its own format, and almost all of them are pairwise incompatible. Exceptions are VCG which uses EDGE's format, and gem uses GraphEd's format. As a consequence, it is quite difficult to exchange graphs between different tools. Not only the syntax is different, there are also several semantic differences: ffl Some formats support only directed or only undirected graphs. ffl Some formats..

GraphEd: A Graphical Platform for the Implementation of Graph Algorithms (Extended Abstract and Demo)

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. Graphs 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

GraphEd: A Graphical Platform for the Implementation of Graph Algorithms (Extended Abstract and Demo)

and Demo) Michael Himsolt Universitat Passau, 94032 Passau, GERMANY [email protected] 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..

Hierarchical Graphs for Graph Grammars (Extended Abstract)

) Michael Himsolt University of Passau 94032 Passau Germany [email protected] Abstract We present HGraph, a data structure for hierarchical graphs which is conceptually based on node and edge replacement graph grammars. HGraph provides three ways to operate on hierarchical graphs : . By graph replacement steps, . By explicit insertion and deletion of nodes, and . By explicit declaration of hierarchy levels. Representations of the graph where parts of the hierarchy are masked can be easily computed. All operations can be carried out efficiently. Applications are all types of structures that are too complex to be viewed as a whole, and need some hierarchical decomposition. In particular, HGraph will be used in the Graph Ed system to handle graph grammar derivations interactively. 1. Hierarchical Graphs Graphs are flexible data structures and can be used to model many types of structures. Examples include data base schemata, Petri nets, VLSI and electrical circuits, data flow..

A View to Graph Drawing Algorithms through GraphEd

We compare a collection of graph drawing algorithms implemented in our Graph Ed system. We report on our experience from running these algorithms on a large number of examples both from the literature and by our own, and present our evaluation of the practical relevance of the algorithms and layout criteria. The representation of complex structures as graphs is widespread. Graph drawing has gained increasing importance in many areas of Computer Science, but has proved to be a difficult task. Our Graph Ed system is an approach to support solutions to this problem. Graph Ed has been used by practitioners for database design, Petri nets and electrical circuits. One of its major applications is the implementation and evaluation of graph layout algorithms. With its capabilities to create and edit graphs, Graph Ed provides an effective environment to create and test large sets of examples. Since all drawing algorithms are built into one tool, it is easy to compare the effect of differ..

An Experimental Comparison of Force-Directed and Randomized Graph Drawing Algorithms

We report on our experiments with five graph drawing algorithms for general undirected graphs. These are the algorithms FR introduced by Fruchterman and Reingold [5], KK by Kamada and Kawai [11], Tu by Tunkelang [13] and GEM by Frick, Ludwig and Mehldau [6]. Implementations of these algorithms have been intergrated into our GraphEd systems [9]. We have tested these algorithms on a wide collection of examples and with different settings of parameters. Our examples are from original papers and by our own. The obtained drawings are evaluated both empirically and by GraphEd's evaluation toolkit. As a conclusion we can confirm the reported good behaviour of the algorithms. Combining time and quality we recommend to use GEM or KK first, then FR and Tu and finally DH

Portable Graph Layout and Editing

The Graph Layout Toolkit and the Graph Editor Toolkit are portable, flexible toolkits for graph layout and graph editing systems. The Graph Layout Toolkit contains four highly customizable layout algorithms, and supports hierarchical graphs. The Graph Editor Toolkit is a tightly coupled interactive front end to the Graph Layout Toolkit