Revision as of 10:27, 4 September 2007

Definition

"Reputation-based systems are used to establish trust among members of on-line communities where parties with no prior knowledge of each other use the feedback from their peers to assess the trust worthiness of the peers in the community." (http://whatifacomputerlies.blogspot.com/2007/04/reputation-system-in-p2p-network.html)

See also our entry on Reputation - Portability

Characteristics of Reputation

From: Manifesto for the Reputation Society by Hassan Masum and Yi–Cheng Zhang

URL = http://www.firstmonday.org/issues/issue9_7/masum/index.html

"Reputation is context–specific. A Ph.D. degree, medical license, or award of merit is meant to certify particular abilities. When a credit agency evaluates your financial history and generates a reputation, the context is your ability to repay loans; this ability may be correlated with but is quite distinct from more general character traits. And reputation could refer to any of these more general traits, like one’s sense of humor or ability to work in a team.

Since there is no absolute objective reputation quantity stamped on people’s foreheads, measurable proxies are necessary, such as book sales rankings, citations in academic papers, Web site visits, and readership of blogs. (Not coincidentally, they have similar highly asymmetric power–law distributions. Many distributions of wealth and of readership of non-electronic resources also follow power–law distributions, a fact noted in Zipf (1949) more than half a century ago.)

Reputation is a surrogate — a partial reflection representing our "best educated guess" of the underlying true state of affairs. Active evaluation by looking behind surface signals can corroborate or disprove reputations, while indiscriminate use degrades their reliability. The challenge is to encourage active evaluation, but also to use it efficiently since it will always be in limited supply.

Emerging information tools are making it possible for people to rate each other on a variety of traits, generating what is really a whole set of reputations for each person. (Information technology is also indirectly increasing the need for such reputations, as we have to sift through more and more possibilities.) You may mentally assign a friend a bad reputation for being on time or returning borrowed items promptly, while still thinking them reliable for helping out in case of real need. No person can be reduced to a single measure of "quality."

So people will have different reputations for different contexts. But even for the same context, people will often have different reputations as assessed by different judges. None of us is omniscient — we all bring our various weaknesses, tastes, bias, and lack of insight to bear when rating each other. And people and organizations often have hidden agendas, leading to consciously distorted opinions.

Reputations are rarely formed in isolation — we influence each others’ opinions. Studying the structure of social connectivity promises to reveal insights about how we interact, and thinking about simple quantities like the average number of sources consulted before an opinion is formed will help us to better filter these opinions.

Are reputations only for people? No, their scope is far wider:

They can be for groups of people: companies, media sources, non–governmental organizations, fraternities, political movements.

They are often used for inanimate objects: books, movies, music, academic papers, consumer products. Typically, whenever we talk about the "quality" of an object with some degree of subjectivity, we can also speak of its reputation, usually as assessed by multiple users — bestseller lists are a simple example.

Finally, ideas can have reputations. Belief systems, theories, political ideas, and policy proposals are the bedrock of public discussion. The waxing and waning of idea–reputations directly affects their likelihood of implementation, and thus the environment that we all share

(http://www.firstmonday.org/issues/issue9_7/masum/index.html)

Design Characteristics

See Table 1 and 2 at http://www.firstmonday.org/issues/issue9_7/masum/index.html

General Definition

From http://www.artsjournal.com/artfulmanager/main/005829.php:

"trust metric = an attempt to measure, assign, and convey trustworthiness among millions of strangers. As you might expect, most trust metrics work on two primary variables:

1) the evidence of your actions in the on-line space (the comments you post, the time you spend reading or participating, the transactions you complete, etc.) and

2) the assessment by other people of that evidence (did you say something smart, did you deliver the product you promised, or did you not, etc.)." (http://www.artsjournal.com/artfulmanager/main/005829.php)

Technical Definition

From the Open Privacy project:

"Reputation: A value that represents the collective opinion of some reference. A reputation is really just another name for an Opinion, as it is the calculated opinion of a Reference by the issuing Reputation Calculation Engine. Reputations are ephemeral, and the weight applied to an Opinion representing the reputation of some Reference is subjectively applied by the end user (person or program) that requests it. As Principals add their Opinion to a Reference, it accrues (positive or negative) reputation capital that has several useful properties:

Secure: Reputations cannot be subverted, and the source of reputation assertions can always be traced. This provides non-repudiation as well as the mechanism with which to decide which reputation information to trust.

Transitive: Reputations are transitive (within the constraints of a well-defined domain). For example, if A trusts B as a source of local news, and B trusts C for local news, then it could be determined that A trusts C for local news." (http://www.openprivacy.org/opd.shtml)

Reputation in P2P Systems

"Generally the reputation system in P2P network follows four steps.

Step 1: a requestor r locates available resources sending a broadcast Query message to ask for the files it needs to download. Other peers will answer with a QueryHit message to the requesting node to notify that they have the requested resource.

Step 2: Upon receiving a set of QueryHit messages, r selects an offerer o and polls the community for any available reputation information on o sending a Poll message. As a result of step 2, r receives a set V of votes, some of which express a good opinion while others express a bad one.

step 3: revaluates the votes to collapse any set of votes that may belong to a clique and explicitly selects a random set of votes for verifying their trustworthiness.

step 4: the set of reputations collected in step 3 is computed into an aggregated community-wide reputation value. Base on this reputation value, the requestor r can take a decision on whether accessing the resource offered by o or not.After accessing the resource r can update its local trust on o (depending on whether the downloaded resource was satisfactory of not)." (http://whatifacomputerlies.blogspot.com/2007/04/reputation-system-in-p2p-network.html)

Examples of Reputation Systems

Applications

From: Manifesto for the Reputation Society by Hassan Masum and Yi–Cheng Zhang

URL = http://www.firstmonday.org/issues/issue9_7/masum/index.html

"The process of filtering information to distill a smaller yet more refined set of usable, verified, trustworthy judgements is not easy. But it is doable. And it is both more feasible and more necessary now than ever before, due to information proliferation, technological advances, and pressing socio–economic problems. Indeed, we already see many types of reputation systems emerging, especially online:

Slashdot has grown to be a prime tech news site largely because of its inspired combination of open contribution and bottom–up filtering, using a modest amount of effort distributed over a large number of people — ranking the thousands of daily comments so one can choose to read just a few gems or all contributions. Similar communities are arising with different focuses, and figuring out why some fail while others succeed will teach us valuable design lessons.

URL = http://slashdot.org/moderation.shtml

Amazon, the online bookselling pioneer that has grown to be a juggernaut, early on made a decision to let users themselves rate each item, optionally accompanied by comments. Browsing through these ratings, suggestions, and warnings can be a gold mine of useful tips, one that is hard to replicate.

eBay uses reputations at the heart of its online auction system, for ranking buyer and seller honesty. Without this feedback, weeding out the bad apples who renege on deals would be far more difficult.

URL = http://pages.ebay.com/help/feedback/evaluating-feedback.html

Google uses derived reputations from Web page interlinking to decide which search results are most relevant, which proved so effective that it has rapidly grown to become a global information utility. It has no "community boundaries," but extends use of reputation to the Web in its entirety.

BizRate and ePinions provide ratings of businesses, seeking to identify those with better product quality and customer service. Both depend on feedback from many consumers, summarizing the experiences of many and in turn influencing future purchasing decisions of consumers in a virtuous feedback loop."

(http://www.firstmonday.org/issues/issue9_7/masum/index.html)

Other examples:

- The Flickr interestingness algorhythm at http://www.flickr.com/explore/interesting/

Dedicated Reputation Systems

Reputation Systems specific to Second Life

P2PRep

"P2PRep is a reputation-based protocol runs in a completely anonymous P2P networks. In P2PReP, local reputation management and community-wide reputation management are two different levels. Local reputation is defined as one single peer’s opinion of one other peer’s reputation, based on its formal experience. The community reputation means the aggregated general opinion given by multiple peers. P2PRep is generally combine these two factors together.

P2Prep works well in the environments of the percentage of malicious peers’ increasing and decreasing by changing well-behaved ones to rogues ones and changing rogue ones into well-behaved ones. As to the turn over case in peers’ population, P2PReP confirms its robust-ness showing a percentage of malicious downloads greater about 1% than scenario with no change." (http://whatifacomputerlies.blogspot.com/2007/04/reputation-system-in-p2p-network.html)

Discussion

Why Reputation is Important

John H. Clippinger on Identity, Reputation, and Social Currency

"Rating and reputation system are a natural and universal artifact of all forms of human cooperation.

Reputation systems are an especially important aspect of social cooperation because they are attached to an individual and form the basis for whether they can be trusted and accepted. A reputation is really the collection of tags that are assigned to an individual or entity to reflect assessments of their competence or status within a specific social network. Given that individuals play different roles in social networks - they can serve variously as connectors, gatekeepers, truth-tellers and enforcers - reputations are tied to roles within social networks.

In eBay, for example, a seller acquires a reputation score given to them by their buyers. Different reputation score levels not only make it more likely that others will do business with them, but it confers a certain status among other members of the eBay community. To encourage participation, many online games depend upon accumulated scores, levels, roles and ratings of players. So do many peer production undertakings such as Wikipedia, Slashdot and open source software development.

Reputation systems are, in fact, linked to all aspects of human endeavor - sports with its performance statistics, education with its grades and degrees, social standard with its board and club memberships. Credit scores are a familiar type of reputation system that is now integral not only to receiving credit, but to participating in society and the economy at large. Credit scores are based upon financial behaviors that are thought to predict the likelihood of default or late payment.

It is not difficult to see how important reputation tags are in small traditional societies where once a reputation is acquired, it may be very difficult to change. Honor-based societies depend upon reputation tags as the principal governance mechanism for defining and enforcing a social order. "Honor killings" of a daughter or sister in order to preserve a familiar reputation suggest the power of reputation in Human Nature. Even in online communities, reputation tags are the motivator and governor of behaviors. People take seriously the reputation scores of an eBay seller/buyer, the accumulated scores of a player of online games, or the number of friends and ratings one has in the online social networks of Linkedin, Orkut, Friendster, Facebook, or My Space.

Identity is not something that can be self-defined. It is granted and modulated by one's roles, relationships, and reputations in a variety of social networks. One's identity (whether it be an individual person, group or organization) is closely tied to reputation tags and roles in social networks. How you see yourself depends upon how other see and rate you.

Reputation tags affect an individual or group's ability to participate within and across different networks, thereby becoming the basis for granting/revoking certain privilege and decision rights. Since reputation tags can be measures of competence by a socially credible third party - e.g., religious, educational, financial, political, trade or professional institutions - they play a very powerful role in governing social mobility and enabling/thwarting interactions between different social networks. By providing information about information - who or what it is, where it came from, as well as marking the rights and privileges for accessing, exchanging, altering, or forwarding goods, services and information, tags are the true control points in self-organizing networks." (http://onthecommons.org/node/723)

See what John Clippinger has to say on Social Currencies, from the same essay.

Reputation is not a collective right

Peter St. Andre argues that reputation is not socially constructed, not tied to collective rights over the individual, but an emergent property of the network:

"It is true that all individuals who wish to productively interact within a community benefit from the existence of reputation as a signalling mechanism; but that does not mean that reputation is a matter of collective interest or group belonging. Reputational signals are used always by individuals within a community and make it easier for those individuals to decide with whom to interact. Thus the benefits of reputational effects are dispersed among all members of the community. But it is a serious error of reification to therefore conclude that the group or community or collective realizes benefits, possesses rights, or pursues actions.

Consider again the analogy to prices. The emergence of prices from economic transactions between buyers and sellers benefits all members of the economic community that is concerned with the product or service at hand (and even members of economic communities concerned with other classes of goods and services, whose prices in turn are affected by the prices of goods and services in the first community). But prices are not therefore the property of all the economic actors in that community, they are not a collective creation of the community, and the group does not have rights to those prices. The same is true of reputation, and it is critically important to recognize the emergent nature of reputation if we are not to be led astray into notions of collective rights that will be inimical to individual participation in online communities." (https://stpeter.im/?p=1427)

For a counter-argument see Beth Noveck's Creating a Legal Framework for Online Identity.

More Informaton

Insightfull commentary by Clay Shirky at [1]