The World Wide Web Consortium yesterday began the final review period for its patent policy.

While emphasizing royalty-free Web infrastructure standards, the W3C plan does allow for exceptions to the policy in rare circumstances, such as when a technology needs to be included in a specification but is not available on a royalty-free basis.

The policy, which is subject to a public review period through April 30, is intended to reduce the threat of blocking patents, in which a particular entity seeks royalties for implementations of W3C specifications because of a contributing technology. W3C Director Tim Berners-Lee will then decide whether to issue the policy as a formal W3C recommendation, the final stage of approval.

W3C, in formulating its policy, is attempting to prevent patent claims from inhibiting development of its industry specifications, said Daniel Weitzner, chairman of the patent policy working group in Cambridge, Mass., which developed the policy.

"What has happened recently is we have had more and more situations in which patent claims have impeded the development of new Web infrastructure," Weitzner said.

The patent policy requires patent disclosures by W3C members when they are aware of their patents being essential to implementation.

The policy provides that:
- All who participate in the development of W3C Recommendation agree to license essential claims, or patents that block interoperability, on a royalty-free basis.

- Under certain circumstances, working group participants may exclude specifically identified patent claims from the royalty-free commitment, with exclusions required shortly after publication of the specification's first working draft.

- Patent disclosures are required of W3C members and requested of anyone else who sees technical drafts and has actual knowledge of affected patents.

- Patent claims not consistent with W3C Patent Policy will be handled through dispute resolution process.

The narrow window for including non-royalty-free technologies is intended to preserve flexibility for unexpected situations. It is to be used in rare cases.

Participants in the working group include: AOL, Apple, HP, IBM, Intel, Lexmark, Microsoft, Motorola, Sun, Xerox and others.