PALO ALTO, Calif., May 27 — For anyone who has hesitated before making a purchase on a Web site, uncertain which brand is preferable, Tacit Software is preparing to introduce an online service that will make it simple to pick the brains of friends and colleagues for opinions and expertise.

Tacit plans to start testing the service, called Illumio, next month. The service allows the user to mine the data on the computers of friends, business associates and others with shared interests on any subjects.

However, Illumio is not a search engine, like Google or Yahoo. The system works by transparently distributing a request for information on questions like "Who knows John Smith?" and "Are Nikon digital cameras better than Olympus?" to the computers in a network of users. The questions can then be answered locally based on a novel reverse auction system that Illumio uses to determine who the experts are.

The system is intended to extend a growing category of software that helps groups collaborate and work together more efficiently. Efforts to create systems that augment the intellectual power of work groups go back to the earliest days of computing technology development. The widespread availability of networks and Web browsers, however, has made such technologies far more accessible in recent years.

"The collaboration space is big and busy," said David L. Gilmour, president and chief executive of Tacit. "We don't consider ourselves a collaboration environment, rather we are about communication and search."

Currently, the privately held Tacit, which was founded in 1997, sells similar technology, known as ActiveNet, to corporate customers like Lockheed Martin, Northrop Grumman, Morgan Stanley and Sanofi-Aventis. The new Illumio version is intended to be used over the open Internet. It will be free for individual users and sold commercially to private groups, although the company has not announced pricing.

Software such as Illumio is representative of the rapid emergence of new markets for digital information, said Michael Schrage, a researcher at the Massachusetts Institute of Technology Sloan School of Management.

"This represents the eBayification of organizations," he said. "The reality is that organizations are run off of informal connections and tools such as this facilitate gray markets in information and interpersonal exchange."

Tacit's top achievement in its software for connecting people and expertise may be in a design that keeps personal information private.

"The biggest problem we had to solve was the privacy problem," Mr. Gilmour said.

Because the information used to determine if someone is an expert on a particular question stays on local computers, Tacit's executives said Illumio would avoid potentially troubling privacy questions. The Illumio software is installed on users' PC's, where it is connected through a software interface to either Microsoft or Google's desktop search programs that index local user content, including documents and electronic mail.

The anonymity offered by Illumio is a significant advantage over other social networking software services that place pressure on users to offer assistance.

The Illumio software uses a reverse auction model to restrict the answer to the best expert. In a reverse auction, sellers compete for the right to provide goods or services. For example, in response to the question, "Who knows John Smith?" each Illumio local system would independently determine who had the best relationship in the network based on parameters such as who had recently exchanged the most e-mail with John Smith.

If the local system found a strong relationship, the local Illumio client software would pop up a request on that user's screen asking whether the user wished to respond to the person asking the question. Initially only the strongest candidates would be notified locally of the query. If that user ignored the request, the reverse auction system would, in effect, lower the bar to ask the person with the next strongest relationship. Then, if there were no responses, the bar would be again lowered until an expert responded. It is possible that difficult questions would find no experts.

The system insures that experts remain anonymous until they agree to answer the query. When a user answers, the connection is made either through the Illumio system, by e-mail or by other channels such as instant messaging or telephone.

In addition to the keywords that make up the question, a user is permitted to send an accompanying message that will help people determine whether they have relevant information to a particular question.

Tacit hopes to market the service by providing Web masters with icons it calls "hot spots." For example, a person running a digital photography or similar Web site could place a hot spot on its home page and then anybody who wanted to join an Illumio network on digital photography could do so by simply clicking on the link.

If they already had the Illumio software, it would automatically add them to the group. If not, it would download and install both the indexing software and the Illumio client software. Illumio is currently available for Windows-based computers.

The potential of Illumio lies in its ability to help small groups of friends and associates tap expertise that they might otherwise not know existed, said Esther Dyson, publisher of Release 1.0, a computer industry newsletter and an Illumio investor. "This is searching your friends' heads as reflected in what's on their computers," Ms. Dyson said.