Since I'm now a few weeks behind on my reviews (the date of this post is when I started writing it...), probably everyone who cares about Google Gears has heard about it by now, so I'll keep this short. Chris talked about the design goals for Gears, for both end users and developers. For end users it boiled down to providing a seamless experience between periods of online and offline activity. For developers the goal was to build incrementally on existing skills and techniques - leveraging all those newly learned Ajax skills rather than replacing them, "preserve existing knowledge and momentum" was the exact phrase. Google themselves plan to support all the major desktop browsers with extensions and plugins, but the implementation is an open standard (an open source) so if you feel the need to have it implemented on your platform of choice you can go ahead and do it yourself.

On to the technical details, Gears has three major components:

• Local Server - basically a local proxy, your application files go into a ManagedResourceStore, which has a manifest, so all your app files can be versioned together, and ResourceStore for any other random web resources your user may access
• Database - an SQLite database with a javascript API
• WorkerPool - a method for supporting javascript concurrency through Erlang-style lightweight processes, no shared memory and communication through message passing

If it was just the LocalServer by itself, this would still have been a useful extension - that's all that's really needed to make your web app work offline, but the Database and WorkerPool components enable a whole different approach to web application development. WorkerPool makes it much easier to write applications which do client side data intensive processing, and Database allows you to build applications which sync back to a central server periodically (similar to how .Net CF + SQL Server Compact applications are intended to work now). Expect to see some startups with innovative products based on Gears in the next few months.

Several code examples and clear explanations, an excellent talk as befits what is obviously a key technology for Google - 5 out of 5.