Yahoo will allow other Web sites to use its technology to build their own search services in a new revenue-sharing scheme announced on Thursday.

Yahoo said it would release the beta version of an API on Thursday that Web sites can use to build services based on its search infrastructure and algorithms, including the ability to rerank results and control how they are presented.

A publisher could use the API to build a search service that specializes in a particular topic, such as sports, for example. Or it could use the API to give users a better way to search the content on its Web site -- or potentially even to build a rival to Yahoo.

The API is part of what Yahoo calls its BOSS platform, for Build Your Own Search Service. The API will be available to any Web developer, along with tools for combining data from Yahoo's search indexes with data from other sources on the Web.

In the coming months it will roll out a "monetization platform," using its advertising system, that will allow Web sites to start generating revenue from the services they build. Yahoo plans to collect a share of the revenue from the sites that use its BOSS platform, said IDC analyst Karsten Weide.

"What Yahoo gets is two things," she said. "They get a cut of the ad revenue, and secondly it makes those Web sites beholden to Yahoo and not somebody else."

Rival search company Google already offers a service that allows Web sites to create custom search engines. But Yahoo contended that its BOSS platform will give an "unprecedented level of access" to its technology in a way that will "disrupt the search market," according to a statement.

Analysts said they don't expect the new offering to significantly boost Yahoo's share of the search market, however. "It will help, there's no doubt about that, but it's not gong to totally turn things upside down. Certainly not in the short term," Weide said.

Two Web sites have already been using BOSS to offer niche search services. Me.dium is a "social" tool that lets people at different computers search the Web and view Web pages as if they were together, while Hakia offers semantic search.

Those sites are examples of the type of specialized services that have not really taken off because Google continues to dominate all kinds of search, said Evan Andrews, search analyst at Jupiter Research. If other Web sites can take Yahoo's search technology and improve on it, then Yahoo might see an impact from this offering, he said.

"If they're able to align themselves with some major partners and collectively bring in traffic and monetize that, then [Yahoo] stands to chip away at market share," he said.

Yahoo said its service would also allow universities to do research into search engines in a way that they have not been able to before.

The offering continues Yahoo's Open Strategy announcement earlier this year, when it described a long term plan to be more open with its Web sites, services and applications. Yahoo's strategy is to "leverage third party contributions to improve their market position and improve their bottom line," Weide said.

Thursday's announcement is unlikely to affect Yahoo's ongoing discussions about a combination with Microsoft. "This has not been designed to annoy Microsoft even more, like the Google search announcement," Weide said. He was referring to a Yahoo agreement to start running some Google ads on Yahoo sites, a deal that some experts say was made in hopes of fending off a Microsoft acquisition .

Yahoo said the beta API and further details of the new service would be available online Thursday at a new BOSS section of its developer Web site.