2009/2/13 PJ Fitzpatrick <[email protected]>:
> Hi,
>
> You mention a very critical point about the network. I worked on the launch
> of an online exchange many years back and a lot of the success has to do
> with how many users you get. However i'm also of the opinion that the actual
> matching algorithmn can have a critical bearing on the success as well.

I'm closer to the data-centric viewpoint myself, as expressed by Anand Rajaraman

http://anand.typepad.com/datawocky/2008/03/more-data-usual.html

> For example assume you can only match with someone who is the exact opposite
> to yourself. I have A and want B and you have B and want A. To find matches
> you then need a lot of users. If however you widen it out to allow say 3
> people to match then you could have a match created if the following occurs.
> -I have A and want B
> -Another user has B and wants C
> -Yet another user has C and wants A
>
> So by allowing these higher order matches you get a much better chance of
> matches actually happening for a smaller number of participants. In my local
> barter website i have taken this to the extreme that i have no limit on the
> number of people that can be matched in such a chain. All i do is, at some
> fixed interval(currently expected to be weekly), i take all the orders and
> try to come up with the matches that maximises (or attempts to maximise as
> it is unlikley i would get the global maximum) the amount of business done
> on the exchange. Of course things becomes impractical if the number of users
> is very high but as i said it is a local barter website.

If I understand correctly, this algorithm tests an element of a set
not just with other elements but with all subsets of elements in the
set which it isn't in? I understand the reasoning, but the the number
of tests for a set of N elements is 2^(N-1)-1. Yikes.

> Anyway one of the reasons i posted this in the first place was to see what
> people though and to see is some other people would be interested in
> participating in an Open Source Project on it. I remember a while back there
> was talk of some project in the Python Ireland group.

I would certainly be interested in helping to develop a project aimed
at creating a knowledge base like this, though I don't know how much
effort I could commit to. Of course the first problem such a site
would face is deciding which stack to use :P

> Also a similar concept could be applied to books. I already have got the
> domain www.ihavereadthebook.com.

Amazon allow third party use of their recommendation engine. You might
want to have a look at that if/when your book project kicks off.

-- 
steev
http://www.daikaiju.org.uk/~steve/

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