Paul Crowley (ciphergoth) wrote in trustmetrics,

A quick explanation of TrustFlow

TrustFlow does not look at interests, who reads your journal, or any other such thing. It looks only at "friends" lists. It's trying to determine who is closest to who based on who lists who as a friend.

Imagine this. Everyone on LJ has a bucket that can hold 500 tokens. We start off with every bucket empty. The order in which TrustFlow lists people is the order in which each person manages to fill their own bucket.

You are the source of tokens; you get tokens one at a time. First, you put them into your own bucket, until that bucket is full. Bang, you are top of your own list. You then give more tokens to your friends, in strict rotation; imagine a parent handing out a bag of sweets to kids "one for you, and one for you and one for you, and a second for you and a second for you...". Each of your friends places the token in their own bucket. Finally, after you've given out 500 tokens for each of your friends, all their buckets fill one after another, and they all join the list.

Since all that is totally predictable, we don't bother to list you or your friends, because it's after that that things get interesting.

You get a token. Since your bucket is full, you pass it to a friend. But their bucket is full too, so they pass it to a friend in turn; like you, they issue the tokens they get to their friends in strict rotation. Each token ends up in the bucket of someone who isn't on the list. Keep going like this, and eventually someone's bucket will fill up. They become the next person to join the list. From then on they, like you and your friends, pass on any more tokens they get to their friends. Keep going until we have 50 full buckets, and list the order the buckets fill up.

That's basically it. There's a slight complication to do with dead ends but that doesn't matter much for the basic understanding.

Here's some of the consequences.
  • Supposing Alice and Bob are on your friends list. Alice has two friends; Bob has 20. All other things being equal, each of Alice's friends gets 10 tokens for every token one of Bob's friends get, because Alice and Bob are receiving just as many tokens but Alice is sharing them between fewer people.
  • If many of your friends list me, I will get more tokens.
  • If you list Alice and Bob, and Alice lists Bob, then in addition to the tokens he gets from you, Bob will sometimes get tokens from Alice. As a consequence Bob's friends get a few more tokens.
  • Who your friends are matter only once you get on the list. It doesn't matter if my friends list is just the same as yours, it doesn't affect my ranking at all; my friends list matters only once my ranking is decided.
  • The "Trust" in "TrustFlow" is there because it's really meant for a different situation - one where you list people to indicate that you trust them. That's emphatically not the case on LiveJournal - LJ was just a handy platform on which to try the ideas out. It doesn't measure trust here, more the sorts of qualities which lead to putting someone on your friends list, which is generally acquaintance and interestingness.
  • The "Flow" is there because the trust starts from you, and "flows out" down the links to your friends, and then onto their friends.
I hope that helps answer some of the questions people have had!
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