Building Web Reputation Systems- P7

Building Web Reputation Systems- P7:Today’s Web is the product of over a billion hands and minds. Around the clock andaround the globe, people are pumping out contributions small and large: full-lengthfeatures on Vimeo, video shorts on YouTube, comments on Blogger, discussions onYahoo! Groups, and tagged-and-titled Del.icio.us bookmarks. User-generated contentand robust crowd participation have become the hallmarks of Web 2.0.
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Building Web Reputation Systems- P7Figure 4-4. A full user review typically is made up of a number of ratings and some freeform textcomments. Those ratings with a numerical value can, of course, contribute to aggregate communityaverages as well.PointsFor some applications, you may want a very specific and granular accounting of useractivity on your site. The points model, shown in Figure 4-5, provides just such a ca-pability. With points, your system counts up the hits, actions, and other activities thatyour users engage in and keeps a running sum of the awards.Figure 4-5. As a user engages in various activities, they are recorded, weighted, and tallied.This is a tricky model to get right. In particular, you face two dangers: • Tying inputs to point values almost forces a certain amount of transparency into your system. It is hard to reward activities with points without also communicating Simple Models | 71 to your users what those relative point values are. (See “Keep Your Barn Door Closed (but Expect Peeking)” on page 91.) • You risk unduly influencing certain behaviors over others: it’s almost certain that some minority of your users (or, in a success-disaster scenario, the majority of your users) will make points-based decisions about which actions they’ll take. There are significant differences between points awarded for reputation purposes and monetary points that you may dole out to users as cur- rency. The two are frequently confounded, but reputation points should not be spendable. If your application’s users must actually surrender part of their own intrinsic value in order to obtain goods or services, you will be punishing your best users, and you’ll quickly lose track of people’s real relative worths. Your system won’t be able to tell the difference between truly valuable contributors and those who are just good hoarders and never spend the points allotted to them. It would be far better to link the two systems but allow them to remain independent of each other: a currency system for your game or site should be orthogonal to your reputation system. Regardless of how much currency exchanges hands in your community, each user’s un- derlying intrinsic karma should be allowed to grow or decay uninhibited by the demands of commerce.KarmaA karma model is reputation for users. In the section “Solutions: Mixing Models toMake Systems” on page 33, we explained that a karma model usually is used in supportof other reputation models to track or create incentives for user behavior. All the com-plex examples later in this chapter (“Combining the Simple Models” on page 74)generate and/or use a karma model to help calculate a quality score for other purposes,such as search ranking, content highlighting, or selecting the most reputable provider.There are two primitive forms of karma models: models that measure the amount ofuser participation and models that measure the quality of contributions. When thesetypes of karma models are combined, we refer to the combined model as robust. In-cluding both types of measures in the model gives the highest scores to the users whoare both active and produce the best content.Participation karmaCounting socially and/or commercially significant events by content creators is prob-ably the most common type of participation karma model. This model is often imple-mented as a point system (see the earlier section “Points” on page 71), in which eachaction is worth a fixed number of points and the points accumulate. A participation72 | Chapter 4: Common Reputation Modelskarma model looks exactly like Figure 4-5, where the input event represents the numberof points for the action and the source of the activity becomes the target of the karma.There is also a negative participation karma model, which counts how many bad thingsa user does. Some people call this model strikes, after the three-strikes rule of Americanbaseball. Again, the model is the same, except that the application interprets a highscore inversely.Quality karmaA quality-karma model, such as eBay’s seller feedback model (see “eBay Seller FeedbackKarma” on page 78), deals solely with the quality of user contributions. In a quality-karma model, the number of contributions is meaningless unless it is accompanied byan indication of whether each contribution is good or bad for business. The best quality-karma scores are always calculated as a side effect of other users evaluating the contri-butions of the target.On eBay, a successful auction bid is the subject of the evaluation, and the results r ...