Trust Network

1
Jennifer Golbeck, Bijan Parsia, James Hendler
Trust Networks on the Semantic Web
Ratings and Ontology
Calculating Trust
Trust Network

• Using our Trust Ontology (an extension of FOAF),
  users create trust ratings for their
  acquaintances
• Individuals are identified by email address
• Ratings are made on a scale of 1-9
• Ratings can be made in general, or with respect
  to a specific concept
• ltPerson rdfID"Bob"gt
• ltmbox rdfresource"mailtojoe_at_example.com"/gt
• lttrustsSomewhat rdfresourceJoe/gt
• lttrustsHighlyRegt
• ltTrustsRegardinggt
• lttrustsPerson rdfresource"Dan"/gt
• lttrustsOnSubject
• rdfresource"http//example.com/ontAutoRepai
  r"/gt
• lt/TrustsRegardinggt
• lt/trustsHighlyRegt
• lt/Persongt

Trust from the source to sink is calculated using
a BFS based algorithm.
where tij is the trust between node i and node
jn is the number of nodes in the graph

• If there is a direct edge connecting source to
  sinkthat value is used as the trust value
• If there is no direct edge
• Find all paths from source to sink (
• Find the max flow on each of those paths
• Use a weighted average of the maximum trust
  capacity of each path as given in the formula
  above

TrustMail
Trust Web Service

• Via a web service that hooks in to a spidered
  graph of the network, users can
• Write their own applications that use the trust
  network
• Create their own trust metrics based on the
  properties of the graph
• Submit class files with their own code to be used
  in existing applications that use the service

Built on Mozilla Messenger, TrustMail displays
the senders trust rating next to each message.
This provides something akin to the opposite of
a spam filter a relevance rating that allows
users to sort messages to see those from the most
trusted individuals first. Consider two research
groups collaborating on a project. The professors
in charge of each group know one another, and
each knows her own graduate students, but neither
knows the students from the other group. With
TrustMail, messages from studentsin one group to
members of the other group will be recognizable
and highly rated because of the intermediate
link between professors. Calculated trust values
can be overridden by simply creating a personal
rating for a given individual. This is always
used in place of the network rating.
TrustBot
Using the web service as a back-end, we have
created TrustBot. This is an IRC bot running on
irc.freenode.net what allows users to access and
control the in-memory graph. They can query, get
help and explanations, and reload the graph after
making changes to their local files