IBM and Linden Labs, the operator of the Second Life virtual world, said on Tuesday they will work on ways to eventually let people use a single online persona in different online services.

Interoperability is emerging as a key goal of the nascent virtual world industry, which attracting hundreds of millions of dollars in investment on the hopes that video-game graphics and rich 3-D environments will supplant flat Web pages.

Currently, people who create a character, or avatar, in one virtual world cannot take that identity into another service.

Designing a detailed avatar can take well over an hour, so a closed system discourages customers from abandoning that investment. But it is also a barrier to growth since few people bother to start the process anew in multiple virtual worlds.

An open system would let people create one avatar that would keep the same basic appearance and customer data no matter where it was in cyberspace.

It is going to happen anyway, said Colin Parris, IBM vice president of digital convergence. If you think you are walled and secure, somebody will create something that's open and then people will drain themselves away as fast as possible.

Linden Labs, whose Second Life is one of the market leaders with about half a million active users, is betting that an open system will reward interesting worlds with more customers and punishes dull ones with an exodus of users.

But such a virtual passport system may be years away, if it doesn't first fall prey to the kind of conflicting interests that occasionally bog down efforts to draw up standards in the fast-changing technology industry.

IBM's Parris said the effort would first focus on studying situations where the ability to travel between virtual worlds is most in demand. The nuts and bolts of how to make different software work together will come later.

IBM and Linden announced the partnership ahead of a virtual worlds conference that starts in San Jose, California on Wednesday and is expected to discuss the formation of industry standards and other issues.

Most participants are start-ups but the event has also attracted services and hardware heavyweights like IBM and Cisco, as well as software and entertainment giants Microsoft and Sony.

The event itself is seen as something of a coming-of-age milestone for an industry that is starting to be taken seriously as a provider of useful business tools and not just a quirky offshoot of the video game sector.

Conference organizers say some three dozen companies that offer virtual worlds or related software and services have attracted about $200 million in investment over the past year -- a figure that rises to $1 billion if you count Disney's purchase of kid-oriented online world Club Penguin, and Intel's acquisition of Havok, whose physics software is widely used to make virtual objects behave realistically.

Software