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Abstract

A graph drawing algorithm produces a layout of a graph in two- or three-dimensional space that should be readable and easy to understand. Since the aesthetic criteria differ from one application area to another, it is unlikely that a definition of the ``optimal drawing'' of a graph in a strict mathematical sense exists. A large number of graph drawing algorithms taking different aesthetic criteria into account have already been proposed. In this paper we describe the design and implementation of the AGD--Library, a library of {\bf A}lgorithms for {\bf G}raph {\bf D}rawing. The library offers a broad range of existing algorithms for two-dimensional graph drawing and tools for implementing new algorithms. The library is written in \CC using the LEDA platform for combinatorial and geometric computing (\cite{Mehlhorn-Naeher:CACM,LEDA-Manual}). The algorithms are implemented independently of the underlying visualization or graphics system by using a generic layout interface. Most graph drawing algorithms place a set of restrictions on the input graphs like planarity or biconnectivity. We provide a mechanism for declaring this precondition for a particular algorithm and checking it for potential input graphs. A drawing model can be characterized by a set of properties of the drawing. We call these properties the postcondition of the algorithm. There is support for maintaining and retrieving the postcondition of an algorithm.