Defining displayed 3D content from external source?

Not sure where to begin here, and it may well be the best answer will be pointers to the correct parts of the API. I'm a rank newbie with Unity and don't know quite where my interest applies.

Here goes...

What I want to do is display a rotatable dynamic 3D graph with clickable nodes. A really big graph. The existance and position of various nodes can change in real time, and all of that information would be fed in from an external source (as yet not completely defined).

Can Unity 3D support this kind of external definition in real time of what is being rendered? If so, where would I begin looking for the right "hooks" so I can evaluate what the capabilities and limitations are? Right now I'm not really sure even where to begin.

Many thanks in advance!