IBM and Yahoo have updated their free enterprise search software, in the wake of new competition from mutual rival Microsoft.

IBM's OmniFind Yahoo Edition receives several enhancements. Users can now generate up to five separate indexes of documents, enabling searches of a particular set as well as the entire repository.

It also now supports additional custom search fields, such as from HTML tags or document metadata.

"If you've created a Word document with customer metadata fields, it will be able to extract it," said Aaron Brown, IBM's director of search and content discovery. IBM also said the software is now easier to install as a Windows service.

OmniFind Yahoo Edition is based on the open-source Lucene project. The update includes the latest version of the Lucene core, according to Brown: "It helps us close the loop with the community, because we've contributed a lot of IBM code back into Lucene."

However, the update does not include any scalability improvements, and remains limited to searching 500,000 documents per instance, Brown said.

Brown said the updates were primarily guided by feedback from customers. The software has been downloaded about 25,000 times, according to IBM. Yahoo and IBM released the first version of the search engine about one year ago.

Microsoft's recent entry into the stand-alone enterprise search market has been seen as potentially disruptive for certain vendors, such as Coveo, but not for search companies offering high-end, specialised products.

Like IBM, Microsoft is adopting a multi-tier strategy around search. Both companies are giving away an offering in the hopes of attracting customers, who will eventually desire greater capabilities and pay for commercial products.

Microsoft's new products, Search Server 2008 and Search Server Express 2008, which is free, will be generally available in the first half of 2008, according to the company.

Brown said Microsoft's move was not unexpected: "We obviously didn't have any inside information. I can't say I was entirely surprised, given where the market is moving."

He said there is "a lot of traction" in Europe for OmniFind Yahoo Edition right now, adding that a range of organisations are using the product, from a small US public school district to a global electronics company, which he did not name.