Yahoo is opening up its search platform so that external developers can create search applications that tap the vendor's search infrastructure. The company said that it is also expanding access to the Overture ad network to more developers.

With the launch of the Yahoo Developer Network, Yahoo is providing access to APIs for a variety of its search services, including web, image, video, news and local search. The company is also broadening access to the Overture APIs, which have been available to high-volume advertisers for several years. Now, other types of Overture users, such as search-engine marketers and smaller advertisers, will be allowed access to the APIs.

"Yahoo can't be everything to everybody," said Eckart Walther, head of product management for Yahoo Search. "This is the first time we're providing formal APIs to developers to write new search applications that run on top of our infrastructure. There are hundreds of ideas (for search applications) we haven't thought of that will be enabled by these APIs."

For example, a developer could create a tool that allows users to display Yahoo search results in a different way, he said. Or the webmaster of a site focused on a particular area or city could use the APIs to build functionality into the site that delivers either automatically or on demand a list of local restaurants obtained from the Yahoo Local service, he said.

The Yahoo Developer Network, offers registered developers a variety of features, such as access to the APIs, sample code, discussion groups, mailing lists and a section that showcases applications created by developers.