Google's Android mobile operating system was designed for smartphones, but it is increasingly being adopted by consumer electronics companies to power a range of new devices, including tablets and e-book readers. As we discovered when we looked at some of the upcoming Android tablet products a few months ago, the platform isn't natively suited for the tablet form factor and will need some refinement in order to deliver a top-notch user experience on devices that aren't smartphones.

Google mobile products director Hugo Barra recently acknowledged this issue in a statement to TechRadar. He says that Android 2.2, codenamed Froyo, is simply not designed for the tablet form factor. He also commented that the Android Market won't be available on tablets that deviate too far from the conventional Android user experience, because such devices won't be able to properly run Android applications.

Google's Android compatibility definition, which describes the mandatory hardware and software features that a product has to support in order to ship with the Android Market, poses challenges for tablet vendors because it stipulates some hardware requirements that may not be practical for tablets—such as requiring devices to have a built-in camera and GPS. As we explained earlier this year, the purpose of such requirements in the compatibility definition is to protect the platform from fragmentation by ensuring that devices which are intended to run third-party software share a baseline level of functional and behavioral compatibility.

A problem that has emerged as Android is expanding to new form factors is that it may be difficult in some cases to adapt the platform to work well on non-smartphone devices without falling afoul of the compatibility definition. Despite the challenges, some vendors like Samsung are building compelling tablet-sized Android products that conform with Google's requirements. As TechRadar points out, this works because the Samsung Galaxy Tab is basically an oversized phone rather than a conventional tablet.

An odd twist in the Android compatibility story is the fact that upcoming products based on the Google TV platform will be able to run Android applications despite the fact that such devices won't even come close to fitting within the constraints of the Android compatibility definition. One one hand, we have a radically new set-top form factor that will supposedly run Android applications, and on the other hand, we have a Google product director saying that Android isn't a good fit for non-smartphone devices and that those devices may pose insurmountable application compatibility challenges in some cases.

Google open source and compatibility program manager Dan Morrill recently weighed in on this issue on the official Android Developers blog. Although Google's official Android documentation on supporting multiple displays doesn't even address sizes that are larger than four inches, he says that existing applications generally behave properly on larger screens. He also says that it won't be difficult for developers to make custom layouts that will allow applications to take advantage of the extra space when it's available.

In his view, the challenge posed by the Google TV product and other radically different form factors can be overcome if developers simply specify Android Market filters in their application's manifest file. This will cause their applications to only show up in the Market on devices that are capable of supporting all of the application's functionality. An application that relies on SMS and the camera, for example, could simply be excluded from the Android Market on Google TV.

"You can use our built-in tools to handle these cases and control which devices your app appears to in Android Market. Android lets you provide versions of your UI optimized for various screen configurations, and each device will pick the one that runs best," he wrote. "Android Market will make sure your apps only appear to devices that can run them, by matching those features you list as required (via tags) only with devices that have those features."

This approach will work, but it will create a certain kind of fragmentation that the Android compatibility definition was intended to prevent. Despite Google's efforts to ensure hardware uniformity between devices, it seems like fragmentation is inevitable. What is most puzzling is the lack of consistency in Google's message about Android on non-smartphone form factors.

It's possible that Android 3.0 will bring solutions to some of these problems. There are already rumors circulating that it will boost tablet support and be better suited for non-phone form factors. If Google's compatibility program can evolve to function as effectively for new devices as it has for smartphones, we could see Google's little robot show up in a lot more places.