Google today announced the availability of a new open-source browser plug-in, Google Gears, that promises developers the ability to create applications that work within a browser — even without Internet connectivity.

Carl Sjogreen, senior product manager for Google, said Google Gears is focused on solving the problem of offline access for Web applications. Once an application is using Google Gears, it handles all the details of locally caching the content for when a user is offline, and will handle the synchronisation of the cached content when the user returns online.

Sjogreen gave the example of the Google Reader: “You install the browser plug-in, you configure all the feeds subscriptions that you are interested in reading — then you can basically unplug the Internet connection, read your news offline, maintain your subscriptions and when you go online again, it will download any news items and update your subscriptions”. The Google Reader is available from today with Google Gears-enabled offline capabilities.

Gears is supported across Internet Explorer, Firefox, Safari and Opera browsers on Windows, Mac OS X and Linux platforms. “We’re trying to make it as cross-browser as possible; obviously there are some cross-browser Javascript issues that are beyond the scope of this particular problem,” said Sjogreen, “but Gears is very consistent across browsers”.

Google plans to work closely with all members of the Web community to converge upon a standard so developers have one consistent API for offline functionality, Google said in a statement. Among the first of Google’s partners is Adobe, which will be offering the Google Gears API in its upcoming Apollo platform.

The plug-in will be around 500K in size and include an SQLite database as a backend. Developers will interact with it using SQL and Javascript; Sjogreen described Google Gears as “a really, big cookie with a SQL interface that you can access from Javascript”.

The information stored in Google Gears is dependent on the developer, according to the search engine giant.

“Because it’s a core technology, it can be used in different applications in different ways … [in] some applications you can really imagine it being completely seamless, every bit of the application is available offline.

“There are other applications which may involve a significant amount of data that you are searching over and some server side processing that is required — not all capabilities of an application may be ‘offlineable’,” Sjogreen said.

Google said the new technology will be able to work with Web applications using AJAX, which doesn’t easily work with caches.

The amount of hard drive space required to run the new technology is said to depend on the number of Google Gears-enabled applications being used and how those applications make use of the offline data.

“Virtually every application that you use on the Internet and every Web site you use on the Internet could take advantage of offline capability,” he said.

“More and more of everyone’s day-to-day life is moving into applications online in a Web browser, and we think that Google Gears is the critical factor in the evolution of Web applications because it addresses a minor anxiety.

“Look at the applications that people use most often, examples like e-mail, calendaring, communication applications of that sort, things that many of us use day-in, day-out and often need access to when we are offline. That sort of personal information application will be very interesting to enable them in an offline fashion,” he added.

Google is hoping to garner comments and contribution from the community to help improve Gears, and has made it available in its early stages so that developers and users can test the capabilities and limitations of the plug-in.

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