Interview: how Google tweaks rank algorithm

nbauman writes: "New York Times interview with Amit Singhal, who is in charge of Google's ranking algorithm. They use 200 "signals" and "classifiers," of which PageRank is only one. "Freshness" defines how many recently changed pages appear in a result. They assumed old pages were better, but when they first introduced Google Finance, the algorithm couldn't find it because it was too new. Some topics are "hot". "When there is a blackout in New York, the first articles appear in 15 minutes; we get queries in two seconds," said Singhal. Classifiers infer information about the type of search, whether it is a product to buy, a place, company or person. One classifier identifies people who aren't famous. Another identifies brand names. A final check encourages "diversity" in the results, for example, a manufacturer's page, a blog review, and a comparision shopping site. If the user has signed in to Google, they can tell whether a search for "dolphins" is by a football fan or marine biologist. Examples of problems that Google identified and tweaked the algorithm to avoid: a search for "french revolution" returned too many results about the French presidential elections. A search for "teak patio palo alto" didn't return a store called the Teak Patio. http://www.nytimes.com/2007/06/03/business/yourmon ey/03google.html Inside the Black Box By SAUL HANSELL, June 3, 2007"