Jaideep Singh, cofounder of the new people-search engine Spock, says he wants to build a profile for every person in the world. To do this, he plans to combine the power of search algorithms with online social networks.

Singh says he got the idea for Spock while looking for people with specific areas of expertise among his contacts in Microsoft Outlook. Although he has two or three thousand people listed, he could only find people he was already thinking about.

Spock is designed to solve that problem by allowing users to search for tags--such as "saxophonist" or "venture capitalist"--and then view a list of people associated with those tags. Singh could have manually entered tags for each of his contacts into Microsoft Outlook, but capturing every interest of each particular individual would be time-consuming. Spock uses a combination of human and machine intelligence to automatically come up with the tags: search algorithms identify possible tags, and users can vote on their relevance or add new tags. Registered users can add private tags to another person's profile to organize their contacts based on information that they don't want to share. For example, a contentious associate might be privately labeled as such.

The social-network component of the website introduces an element of crowd commentary into the search process. George W. Bush is tagged "miserable failure," with a vote of 87 to 31 in favor of the tag's relevance as of this writing. Users aren't allowed to vote anonymously, and the tag links to the profiles of people who voted.

Singh hopes social networks will also help with one of the main problems in people search: teaching the system to recognize that two separate entries refer to a single person--a problem called entity resolution. For example, a single person might have a MySpace page, a Linked In profile, and a write-up on a company website. Steven Whang, an entity-resolution researcher at Stanford University, says that there are several aspects to the problem: getting the system to compare two entries and decide whether they are related, merging related entries without repetition, and comparing information from a myriad of possible sources online. Finally, Whang says, there is a risk of merging two entries that should not be merged, as in the case of a name like Robin, which is used by both men and women.

Many of the people-search engines try to get around these problems by encouraging people to claim and manage their own profiles, although Whang notes that this is a labor-intensive approach. Although there are many sites where people could claim their profiles, Singh says he thinks one engine will eventually dominate, and people will make the effort to claim profiles there. Bryan Burdick, chief operating officer of the business-search site Zoominfo, says that 10,000 people a week claim their profiles on Zoom, in spite of having to provide their credit-card numbers to do so.

Singh has also introduced the Spock Challenge, a competition to design a better entity-resolution algorithm. He says that 1,400 researchers have already downloaded the data set, and they will compete for a $50,000 prize, which will be awarded in November.