A recent NY Times article that is lighting up the search blogosphere called Google Keeps Tweaking Its Search Engine by Saul Hansell provides some insights on how the Google ranking system works. For anyone that has ever spent some time tweaking ranking metrics, this is an article worth checking out. Here are some snippets:
“Someone brings a query that is broken to Amit, and he treasures it and cherishes it and tries to figure out how to fix the algorithm,” says Matt Cutts, one of Mr. Singhal’s officemates and the head of Google’s efforts to fight Web spam, the term for advertising-filled pages that somehow keep maneuvering to the top of search listings.
Some complaints involve simple flaws that need to be fixed right away. Recently, a search for “French Revolution” returned too many sites about the recent French presidential election campaign — in which candidates opined on various policy revolutions — rather than the ouster of King Louis XVI. A search-engine tweak gave more weight to pages with phrases like “French Revolution” rather than pages that simply had both words.
At other times, complaints highlight more complex problems.
Mr. Singhal introduced the freshness problem, explaining that simply changing formulas to display more new pages results in lower-quality searches much of the time. He then unveiled his team’s solution: a mathematical model that tries to determine when users want new information and when they don’t. (And yes, like all Google initiatives, it had a name: QDF, for “query deserves freshness.”)
THE QDF solution revolves around determining whether a topic is “hot.” If news sites or blog posts are actively writing about a topic, the model figures that it is one for which users are more likely to want current information. The model also examines Google’s own stream of billions of search queries, which Mr. Singhal believes is an even better monitor of global enthusiasm about a particular subject.
As an example, he points out what happens when cities suffer power failures. “When there is a blackout in New York, the first articles appear in 15 minutes; we get queries in two seconds,” he says.
Mr. Singhal says he tested QDF for a simple application: deciding whether to include a few news headlines among regular results when people do searches for topics with high QDF scores. Although Google already has a different system for including headlines on some search pages, QDF offered more sophisticated results, putting the headlines at the top of the page for some queries, and putting them in the middle or at the bottom for others.