5 Graph Description Language (GDL) - Absint

5.6.5 Combination of Features
Figure 28: Example 11, tree layout, smanhattan_edges: yes
The following example (see Figure 29) is taken from [GKNV93] and shows the dependencies of
different shell programs. A combination of aiSee features has been used to visualize it. There is
a time scale to indicate the origin of the programs. The shells themselves are nodes that have to
be placed at the same rank as their birth dates. The level attribute is used to set the nodes at these
positions. In addition, the time axis should be positioned at the left side of the shell dependence
graph. This is achieved by the horizontal_order attribute at some of the nodes. However, this
attribute doesn’t work unless the graph is connected, which is why three invisible edges are created.
Like any other edges, invisible edges influence the positions of the nodes. They pull their adjacent
nodes together. To avoid this effect on the invisible edges, the priority of the invisible edges is set to
zero and the priority of the visible edges to 100. There are many ways to change the priority. The
priority attribute can be set, and the factors layout_downfactor, layout_downfactor and layout_downfactor
as well. The real priority of a downward edge is the product layout_downfactor
x priority.
The Bourne shell should be positioned to the left of the Mashey shell and the csh shell to the
right of the Mashey shell. Therefore, the level two nodes receive a horizontal order. However, csh
is on level three, and only its edge crosses level two. Therefore, the horizontal_order attribute is
set for this edge as well. Now the edge is drawn to the right of the Mashey shell.
Default attribute specifications are used for the height, width and border width of nodes and for
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