[foaf-dev] FOAF-based whitelisting project

Tom Heath tom.heath at gmail.com
Mon Mar 12 23:55:12 UTC 2007

[resending an earlier message; must learn to use reply-all; thanks
Dave for the tip-off]

Hi Dave,

> > I quite like the idea of a 0-1 score (rather than 0-100), and in
> > common with Steve's mail that's just arrived, I'm also skeptical about
> > negative trust ratings; what would we *actually* do with them?. Surely
> > all we need is a score somewhere between 0 and 1, or NULL where we
> > don't have any data?
> Yes, but how do you relate a 0-1 score with a foaf:knows that has no
> value in it?  Do we have some setting that equate foaf:knows to 0.8
> trust and foaf:interest to 0.4 and foaf:spouseOf to 0.9 (as examples)?

I'm sure Kjetil will correct me if I'm wrong (quite possible ;), but
my understanding was that the trust metric(s) would be based on
network distance - the further away in the network, the lower the
score. So, someone three foaf:knows away may have a score of 0.2 (or
whatever), whereas someone I foaf:know could be 0.9 by default. I'm
very dubious about the value of refining/defining relationships at a
more fine-grained level, as apart from something like a family history
application where the nature of the relationship is *the* most
important feature, it's not actually clear what we'd do with the
information. If I have a rel:significantOther, the meaning of that in
functional terms varies wildly depending on the context. Without
further primary research, finer-grained definitions of relationships
are useless for this application IMO. In contrast, I imagine we can
all agree that as a rule of thumb we trust people we know (not to send
us spam) more than we do an average stranger, but that trust decays
with greater network distance.

> Do we have some setting that equate foaf:spouseOf to 0.9

You only trust your spouse 0.9 to not send you spam?? ;)

> And then would the setting be system-wide, or per user that is issuing
> the trust query, or does the truster/knower in the relationship set what
> he wants his foaf:knows to mean, or can the truster/knower specify
> specific values for each relationship if he wants to be detailed and
> precise?

I envisage something very simple whereby the system uses a common
heuristic to compute the trust metrics, but that users set the trust
threshold that the senders of incoming messages must exceed if their
messages are to be delivered. This threshold setting could be done in
terms of 0-1, or in terms of hops in the network, depending on which
is most usable, and what metrics are developed in the end. Kjetil or
others might well have more to add.

Hope that's clear, and preferably useful in some way :)



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