prog/lib to draw graphs

[Florian Lindner]

Hello,
I'm looking for a program or python library to draw graphs.
They should look like the that:


/--------\                         /--------\
| Node A | ------ belongs to ----> | Node B |
\--------/                         \--------/

Which is a result of the function call like that:

connectNodes(firstNode, secondNode, description, lineStyle)
connectNodes("Node A", "Node B", "belongs to", dashed)

It should have a open scalable vector format as output (DVI, SVG, PDF, ...)
and should be able to make automatic optimal placement of the items.
Do you know something like that?
Thx,
Florian