BLAG is a batch application which reads an input file describing the topology of the graph to be drawn, applies the algorithms and the constraints specified in a configuration file, and generates an output files defining a layout if the input graph (i.e. providing coordinates for its nodes and bends).

BLAG is provided as a plug-and-play "server" for novice developers and for advanced developers with standard graph-drawing needs. The BLAG is also the easiest way to enhance legacy applications with graph-drawing capabilities. Finally, application developers can read the source code of BLAG as an example of how easy and effective the GDT Graph API is.



  1. The topology of the graph to be drawn is loaded from the input file.
  2. The layout directives and constraints to be applied are loaded from the configuration file.
  3. Preconditions are checked against the layout algorithm specified in the configuration file (an error message is generated when any of the preconditions is not satisfied).
  4. Three output files are generated, with the same name of the input one, and with three different extension: a .gdt file (in the standard GDT format for drawable graphs), a .exp file (in a simplified export format, specifically designed to interface external applications), and a .fig file (the own file format of the application "xfig" under Unix).

Last update : July 31, 2002
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