Number: 239
Title: headlabel and taillable wrong way round
Submitter: Dylan Hall
Date: Sun Dec 29 22:23:37 2002
Subsys: Dot
Version: 1.8.9
System: x86-Linux-debian stable
Severity: minor
Problem:
I'm using graphviz to draw network diagraphs for an ethernet network. A "dot" file is created with a perl script, then passed to dot.

> dot -Tpng output.dot -o output.png

The resulting file appears to have the headlabel and taillabel switched on the edges between: "x11.engops.tsnz.net" and "x13.engops.tsnz.net" "s36-usya01-r31.engops.tsnz.net" and "a1"
Input: 

// topology information
graph "test" {
        edge [ color=red labelfontsize=8 ]
        "x12.engops.tsnz.net" [ shape="box" label="x12" ]
        "x12.engops.tsnz.net" -- "u12.engops.tsnz.net" [ headlabel="ge1/0" taillabel="1:3" ]
        "x12.engops.tsnz.net" -- "x13.engops.tsnz.net" [ headlabel="2:1" taillabel="1:6" ]
        "x12.engops.tsnz.net" -- "x11.engops.tsnz.net" [ headlabel="2:5" taillabel="3:6" ]
        "x11.engops.tsnz.net" [ shape="box" label="x11" ]
        "x11.engops.tsnz.net" -- "u11.engops.tsnz.net" [ headlabel="ge1/0" taillabel="1:3" ]
        "x11.engops.tsnz.net" -- "x13.engops.tsnz.net" [ headlabel="1:1" taillabel="1:6" ]
        "x11.engops.tsnz.net" -- "s36-usya01-r31.engops.tsnz.net" [ headlabel="1:2" taillabel="1:7" ]
        "x11.engops.tsnz.net" -- "s36-usya01-r31.engops.tsnz.net" [ headlabel="1:1" taillabel="2:8" ]
        "x13.engops.tsnz.net" [ shape="box" label="x13" ]
        "s36-usya01-r31.engops.tsnz.net" [ shape="box" label="s36-usya01-r31" ]
        "a1" [ shape="ellipse" label="CPE/Unknown" ]
        "s36-usya01-r31.engops.tsnz.net" -- "a1" [ taillabel="7:14" ]
        "a2" [ shape="ellipse" label="CPE/Unknown" ]
        "s36-usya01-r31.engops.tsnz.net" -- "a2" [ taillabel="8:14" ]
}
Output file: b239.png
Comments:
Is this a bug or am I doing something dumb?

[erg] The problem is that the graph libraries do not support notions of head and tail nodes for undirected graphs. The simplest fix is to use a directed graph. If you don't want arrowhead (the default for directed graphs, set dir=none for edges.

After further consideration, we decided to change the libraries to support an implied directionality with undirected edges.
Owner: north
Status: Fixed (15 January 2003)