To use the beta program, a participant starts an application called a viewer, the best example being the Second Life client. The viewer renders the virtual world and provides the controls for the avatar. Just like using a Web browser to log in to a website, the viewer is where a log-in request is initiated.
The log-in request is sent to the agent service, which stores things like the avatar’s profile, password, and current location. As part of the beta, Linden Lab has implemented a proprietary version of the agent service running on a test grid. The avatar service now contacts the region service for the right placement of the avatar in the virtual world.
The region service is basically the Web server of virtual worlds. It is responsible for simulating a piece of the virtual landscape and providing a shared perspective to all avatars occupying the same virtual space. A collection of regions is called a grid. Linden Lab has proprietary code running all the Second Life regions. The OpenSim project provides source code that, when built, allows anyone to run his or her own region service.
From that point on, there is a three-way communication between viewer, agent service, and region service to provide the user’s in-world experience. When the user wants to move to another region, he issues a teleport command in the viewer, and the same process happens. But in this case, the user is not required to log in again, even if the destination region is running on a non-Linden Lab server.
Last fall, Linden Lab formed the Architecture Working Group (AWG), which is the driving force behind the Open Grid Protocol–the architectural definition of interoperability. The team decided that the first step was to focus on the areas of log in and teleport. “We started with authentication information and being able to seamlessly pass the log-in credentials between two grids run by different companies,” says Levine. “Many people ask me, ‘Why did you start there?’ Well, you can’t do all the rest until you get logged in.”
Miller says that in the next 18 months, a user can expect to see a lot of activity in the area of content movement. “How do I move content that is mine, purchased or created, between worlds safely and securely? The AWG has a lot of great thoughts on how this could work,” he says.
Brian White writes a virtual world blog, Virtual White: An Exploration of Virtual Worlds.