Node Diagram Framework

Hi all,

I was just recently tasked by a client to make a simple node diagram web-app. Essentially the user will drag nodes onto a canvas that can take up to 8 inputs and has 8 outputs. Each node will take an input number, do some math on it and output another number. These nodes can be chained together to produce a final calculated number. For anyone familiar with Matlab or even a node editor in things like Maya, Shake, Nuke etc. this is kinda what I am going for.

I am planning on doing this with Flex and AS3.

What I am looking for is a open source diagramming framework that I can leverage to accomplish this without having to write everything from scratch. Essentially having the node components and the line connections between them already programmed allowing me to extend it to fit the needs of my application. I did some searching and found a few commercial options, but nothing that is basic enough for me to use and extend.

Anyone have any ideas on this topic?

Thanks everyone!