Tool for generation of function or data flow diagrams

I am looking for a command line tool which can generate function flow diagrams from some textual description (any sort of markup language would do).

The idea is to document the data connections between some components. The resulting diagrams shall resemble the following. This is mostly for own internal doc. so it doesn't really need to generate fancy diagrams. Blocks with annotation, connections with annotation and maybe some notes is definitely sufficient.

http://www.automation.com/images开发者_如何学Go/article/mathworks/MathWorks_Simulink_robot_arm_simulation_model.png

http://www.randservice.com/images/screen2.jpg

Thanks a lot in advance,

Paul

Check out: GraphViz -- It generates graphs out of a list of vertices and edge definitions

Also, check out IPE, a vector drawing program that can create exactly what you want, but it will be a manual process.