[p2p-hackers] Re: Memory and reputation calculation

[Tim Benham]

> From: MULLER Guillaume <muller at emse.fr>
> Date: Fri, 10 Dec 2004 09:33:39 +0100
> To: p2p-hackers at zgp.org
>
> Hi all,
>
> Right, I would have cited Dellarocas' papers also because he is the only=20
> one I know that worked on this subject.
>
> However, IMHO, his claim that size of history doesn't matter is false.=20
> He took this conclusion in very a specific domain that is eBay-like=20
> market-places with very specific assumption (cf. cited paper).
>
> My idea is that size of history DOES matter. Let's imagine a system=20
> (even eBay-like) where every agent *knows* that the history is a list of=20
> the X last encounters experiences. Then it is easy to see that cheating=20
> 1/X times  is a strategy that pays off (particularly in systems where=20
> ratings might be noisy).
>
> IMHO, the key point with respect to the history is that others should=20
> not be able guess its size. If it has a fixed size, I believe it doesn't=20
> matter if (and only if) other can guess its size (and therefore cannot=20
> use strategy as described above).
>
> However, I'm sorry I didn't have time to make any experimentations, but=20
> I'd like to hear if anybody has.

(1) You'll never eliminate cheating.

(2) Making the size of the history file a secret is probably unworkable. 
Better to make deletion from the history non-deterministic, so the longer a 
record has been been in the list the more likely it is to get dropped. A 
potential cheater would never be certain when the incriminating evidence 
would be gone. 

If which records were disreputable was known then their lifetime could be 
extended.

cheers,
Tim