lightweight distributed trust propagation
TRANSCRIPT
Lightweight Distributed Trust Propagation
(daniele quercia & stephen hailes & licia capra)
What I do...
Research @ ...
What I research...
Reputation Systems for Mobiles
Daniele Quercia
Situation: People exchange
digital content
Daniele Quercia
Problem: Content overload
Daniele Quercia
Proposal: Accept content only from reputable people
Daniele Quercia
Take two devices…
A B
Daniele Quercia
A B
Shall I accept content from B?
Daniele Quercia
A B
A should set its initial trust for B
Daniele Quercia
A B
A should set its initial trust for B
Yes, but how?
Daniele Quercia
Traditional way: Trust propagation ?A B
C
Daniele Quercia
That way works on the Web and has been tested on “binary” ratings
Daniele Quercia
If that way is tested on 3-level ratings
Conclusion: A needs a new way for propagating its trust in B
Conclusion: A needs a new way for propagating its trust in B
But which way?
Our proposal
Daniele Quercia
1
?A B
C2
AB
AC CB
Daniele Quercia
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?A B
C2
1 2
?
Put trust relationships in a new graph & label graph nodes
AB
AC CB
Daniele Quercia
1
?A B
C2
1 2
?
Put trust relationships in a new graph & label graph nodes
AB
AC CB
Define a “good” function that rates AB
f
Daniele Quercia
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?A B
C2
1 2
?
build_graph(trust_relationships, AB)
AB
AC CBf
find_f
<build_graph>
A B
DC3
2
1
1
2
?
A B
? ?
2 3
1
0.5 1
M M
A B
DC3
2
1
1
2
?
A B
? ?
2 3
1
0.5 1
M M
What are those ?
Remember, we’ll define f We will see that f rates neighbouring nodes alike
It’s a neighbour of AB;
therefore, it rates as AB does?
Remember, we’ll define f We will see that f rates neighbouring nodes alike
It’s a neighbour of AB;
therefore, it rates as AB does?
Find relationships that rate as AB does
Remember, we’ll define f We will see that f rates neighbouring nodes alike
It’s a neighbour of AB;
therefore, it rates as AB does?
2 Types
of those relationships
1. The relationships with same rater (A)
A B
DC3
2
1
1
2
As long as B and D behave alike
A B
DC3
2
1
1
2
2. The relationships with same rated node (B)
As long as A and C rate alike
OK, 2 Types
Taking those relationships, one comes up with …
…a graph!
A C
A B
A D C B
2 3
1
0.5 1
M M
</build_graph>
<find_f>
A C
A B
A D C B
2 3
1
0.5 1
M M
Take f that returns the ratings already there ( )& similar ratings for neighbouring nodes
A C
A B
A D C B
2 3
1
0.5 1
M M
2 3
More formally, …
We find f that minimizes that loss!
</find_f>
Daniele Quercia
1
?A B
C2
1 2
?
build_graph
AB
AC CBf
find_f
Does it work? Useful, Robust, Fast, “Light”?
Daniele Quercia
Useful? Tested on real data (Advogato: > 55K user ratings)
Daniele Quercia
Useful? Tested on real data (Advogato: > 55K user ratings)
Daniele Quercia
Robust?
Daniele Quercia
Robust?
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Fast and “Light”?
Daniele Quercia
Fast and “Light”?
For propagating AB (worst case)
Transmit 30KB& run for 2.8ms
Daniele Quercia
All this on …
Daniele Quercia
All this on …
Daniele Quercia