Need UI Advice

[mendhak]

Let's start this by looking at the image of the graph I have attached here.

The nodes on the graph represent "topics" and the lines represent "relationships" between those topics.

My question is essentially, "How would I represent this on a web page?"

Before that though, let me explain what the web page will do.

The web page will start by displaying a choice between the initial nodes 1 and 2.

When the user picks node 1, he will be presented with all the relationships available from that node (relationship = line). Once a relationship is picked, the nodes related are shown. And then its relationships, and so on.

The user eventually selects a node and assigns it a "weight" (the purpose of which is irrelevant to our discussion).

At any point, the user may decide that a relationship exists between 1 and 5, and decides to add it.

Or, a user may decide that a new topic can be related to another topic, such as 8 and 9 as shown, and he will decide to add it.

With these 'constraints' (features?) in mind, how would I go about designing a UI for this? In my second attachment, I have shown a very simplistic UI. It is linear, the user selects only one node, and each node/relationship is being represented by a dropdown box.

How would you represent this? What do you think would make it better?