Reputation & Trust

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Denis GilletAdrian Holzer

“what is generally said or believed about a person’s or thing’s character.”

Reputation

“the extent to which one is willing to depend on another in a situation with a feeling of security, even in the face of possible negative consequences.”

TRUST

How is trustworthiness measured?

Trust in physical world

Derived from

personal experience

Influenced by received referrals from others

Trust related information

shared within local

communities

Trust in online environments Real-life evidences of trust are missing

Need adequate

electronic substitutes

for traditional cues

Trust related information shared on a global scale

A reputation score is associated with an item

The score is calculated by aggregation of all people’s trust opinions

The score is visible to the entire community

The score represents the trustworthiness

Examples

The reputation system incites sellers to be honest

Buyers use sellers’ reputation scores to assess the quality of sellers’ service

Sellers gain reputation when receiving positive ratings

Buyers provide a rating score to sellers

Rank reviewers (Advisor, Top Reviewer, Category Lead) Trust network (trust/distrust a person)

a professional community for eGovernment, eInclusion, eHealth

(L. Page, “The PageRank Citation Ranking: Bringing Order to the Web”, Technical Report, 1998)

Define different contexts

Specify a user’s reputation score depending on a

particular context

A user’s reputation score in Computer Science is high

Her reputation score in Chemistry is low

with current systems

Problems

Raters don’t directly benefit from rating items

Low incentive for providing rating

!

People hope to get a positive rating in return

Positive rating bias

!

Some people provide unfair ratings due to personal reasons

Unfair ratings

People with low reputation scores change their identities and enter the community as newcomers

Change of identities

POSSIBLE SOLUTIONS

Bias toward positive ratingsAllow anonymous ratings

Give extremely low reputation score to newcomers

Effective incentive mechanisms are needed

Exclude or give low weight to presumed unfair ratings, using statistical analysis

Low incentive for providing rating

Unfair ratings

Change of identities