Last updated: May 25, 2007 2:24 pm

Google's search policy puts the user in charge

There was a survey conducted in America in the 1980s that asked people a deceptively simple question: "Who was shot in Dallas?" For many who had lived through the national trauma of 1963, the deliberations of the Warren Commission, the theories about the grassy knoll and the magic bullet, there was only one answer: JFK. For others, who followed every twist of the Ewing family, the oil barons' ball and Cliff Barnes's drink problem, there was also only one answer: JR.

The point of the survey was to show how the same words can have very different meanings to different people depending on their background and their interests. It is the same idea that is driving Google's personal search service.

Our search algorithm is pretty sophisticated and most people end up with what they want. But there is inevitably an element of guesswork involved. When someone searches for "Paris" are they looking for a guide to the French capital or for celebrity gossip? When someone types in "golf" are they looking to play a round on the nearest course or to buy a Volkswagen car? An algorithm cannot provide all the answers.

But if an algorithm is built to take into account an individual's preferences it has much more chance of guessing what that person is looking for. Personalised search uses previous queries to give more weight to what each user finds relevant to them in its rankings. If you have searched for information about handicaps or clubs before, a search for "golf" is more likely to return results about the game than the car. If you have been checking out the Louvre, you are less likely to have to wade through all the details of a particular heiress's personal life.

This makes search more relevant, more useful and much quicker. But it is not for everybody. As the Financial Times has pointed out this week, personalised search does raise privacy issues. In order for it to work, search engines must have access to your web search history. And there are some people who may not want to share that information because they believe it is too personal. For them, the improved results that personalised search brings are not matched by the "cost" of revealing their web history.

The question is how do we deal with this challenge? Stop all progress on personalised search or give people a choice? We believe that the responsible way to handle this privacy issue is to ask users if they want to opt in to the service. That is why Google requires people to open an account and turn on their personalised search functionality. They do not have to give a real name to open a Google account, but even if they cannot be identified, we think they should have to give explicit consent before their web history is used. Unless they do, they will simply have the standard Google search service.

Our policy puts the user in charge. It is not something Google seeks to control. At any time they can turn off personal search, pause it, remove specific web history items or remove the whole lot. If they want, they can take the whole lot to another search engine. In other words personalised search is only available with the consent ofthe user.

If you think of search as a 300chapter book, we are probably still only on chapter three. There are enormous advances to be made. In the future users will have a much greater choice of service with better, more targeted results. For example, a search engine should be able to recommend books or news articles that are particularly relevant - or jobs that an individual user would be especially well suited to.

Developing more personalised search results is crucial given how much new data is coming online every day.The University of California Berkeley estimates that humankind createdfive exabytes of information in 2002 - double the amount generated in 1999. An exabyte is a one followed by 18 noughts. In a world of unlimited information and limited time, more targeted and personal results can really add to people's quality of life.

If you type "Who was shot in Dallas?" into Google today, the results are as divided as the survey's respondents a quarter of a century ago. But with personalised search you are more likely to get the "right" result for you. Giving users the chance to choose a search that is better for them as individualsis something we are proud of andwill continue to build on. After all, the web is all about giving people - you and me - more choice and more information.

The writer is global privacy counsel for Google

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