WANITA SHERCHAN, IBM Research-Australia
SURYA NEPAL and CECILE PARIS
CSIRO ICT Centre
Presented by Jacob Couch
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Trust is considered to be a psychological state of
the individual, where the trustor risks being
vulnerable to the trustee based on positive
expectations of the trustee’s intentions or behavior.
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Cognitive
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Emotive
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Behavioral
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Trust is considered to be a bet about the future
contingent actions of the trustee.
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Considered a level of expectation within a group.
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Cognitive
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Behavioral
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Emotive builds over time
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Inherently personalized
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Based on previous experience
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Direct Trust
–Based
on interactions between users of a system.
–Strength
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is determined based on frequency.
Recommended Trust
–Experiences
of Direct Trust are reflected to neighbors
based on experience and sociability
“The expectation that a device or system will
faithfully behave in a particular manner to fulfill its
intended purpose”
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–TPM
Trust Types/Facets
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Calculative
Relational
Trust Properties
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Context Specific
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Dynamic
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Propagative
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Non-transitive
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Composable
Emotional
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Cognitive
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Institutional
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Subjective
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Dispositional
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Asymmetric
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Self-reinforcing
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Event Sensitive
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“Calculation on behalf of the trusted designed
to maximize the trustor's stakes in the
interaction”
Typical economic model
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Trust built up over time.
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Typically used in employee relationships
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“The perceived outcome of direct interpersonal
relationships [sic]”
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“Trust based on reason and relational
behavior”
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Information channels
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Norms
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Sanctions
“Positive referrals … increase cognitive trust in
the trustee”
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“Trust derived from a provided environment
that encourages cooperation and penalizes
misbehaviors [sic]”
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“...over the course their lives, people develop
generalized expectations about the
trustworthiness of other people”
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Context Specific
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Dynamic
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Propagative
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Non-transitive
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Composable
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Subjective
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Asymmetric
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Self-reinforcing
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Event Sensitive
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“Trust is context specific in its scope”
Would you trust your mechanic to be your
dentist?
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“Trust can increase or decrease with new
experiences”
As a relationship decays, the amount of trust
typically decreases
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“Alice trusts Bob who in turn trusts John”
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Alice can derive some amount of trust on John
Trust can be based on the friend of a friend
mode, but it is not transitive
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“Alice trusts Bob who in turn trusts John”
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This does not imply that Alice trusts Bob
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Alice trusts Bob and Charlie. Charlie trusts
John. Bob trusts John
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Trust through propagation can be composed to
create a greater trust.
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Social trust is subjective to the rater.
If Alice thinks that Bob's opinions are good,
John may not think that Bob's opinions are
good.
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Trust is asymmetric between members of a
relationship.
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The amount that Alice trusts Bob is not the same
amount Bob trust Alice
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“Members act positively with other members
whom they trust.
“if the trust between two members is low... it is
unlikely that they will interact”
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“Trust take a long time to build, but a single
high-impact event may destroy it completely”
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Statical/machine learning
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Artificial Neural Networks
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Hidden Markov Models
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Heuristics
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Behavior based
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Social pattern to associate with similar others
Social properties include race, ethnicity, age,
religion, eduction, occupation...
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The concept of the “Kevin Bacon” effect.
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All persons are connected within 6 degrees
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Most modern social networks use friend of a
friend as a boundary of private information.
The underlying, but not necessarily correct,
assumption is that friendships are transitive.
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No universal agreeable definition
“. . . a collective resource that facilitates
cooperation at the small group level. . . . no
longer resides with an individual but exists
through relationships between actors . . . is
based on the density of interactions . . . ”
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Aspect of social capital that represents
cooperative infrastructure.
“By analogy with notions of physical capital
and human capital—tools and training that
enhance individual productivity— ‘social
capital’ refers to features of social organization
such as networks, norms, and social trust that
facilitate coordination and cooperation for
mutual benefit.”
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Attitudes
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Behaviors
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Experiences
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“And individuals degree of like or dislike”
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Affect
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Behavior
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Emotional response that indicates personal
preference
Tendency of an individual
Cognition
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Beliefs about an object
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Perception of members through interactions
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Must be measured through feedback
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Patterns of interactions
Trust is the community is measured by the
frequency of interaction
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Network Structure/Graph-Based Trust Models
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Interaction-Based Trust Models
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Hybrid Trust Models
Requires feedback from user on interactions
● Golbek proposes FOAF rating on a scale of 1-9
● Ziegler/Hang propose method to calculate trust
between two groups of people on aggregate of
ratings
● Caverlee proposes feedback rating mechanism
after each social interaction
● Maheswaran proposes social trust based on
ratings plus social network connectivity
Bases model purely on interactions of members
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Nepal proposes model on popularity trust and
engagement trust
Adali proposes model based on conversation
trust and propagation trust
Combines Network structure and Interactions
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Trust Based Recommendation Models
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Provide per object recommendations to user
Visualization
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Provide visualization to user to show
trustworthiness of members for general
consumption


Computer Science trust is normally numerical
and comparing against a threshold,
Sociological and psychological responses
should also be evaluated.
Properties such as asymmetry, selfreinforcement, and event sensitivity are
typically not evaluated in the trust equation.


Evaluation of Tie-Strength
Visualization of Trust
◦ Can be used to help service providers identify
healthy and unhealthy networks

Resistance to malicious attacks in P2P
systems
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Trust models in modern online social networks
are still very primitive
Human social network properties can be
ported to online social, thus allowing the use of
existing sociological research
Social capital can be used to cultivate trust of
an online social network