Maybe if you tell us what you are trying to do (give code if you can) we can figure out what (if anything) might be missing.

For example, finding a "previous node" isn't always possible using just the node graph. If two or more nodes connect to this node, which one is previous? However, it is trival to store the number of the last node in the entity, so they know which node they visited last.

Also, as JCL pointed out, paths can go both ways. This can be very handy in some cases, for example: it might be valid for an AI to jump off a roof into a pool, but it isn't valid for him to jump from the pool back onto the roof.


In short, I think you might be looking for the wrong tools to solve a problem.