Microsoft banks Windows Phone 7 on Silverlight

Ubiquity, once more

Furthermore, there's the question of whether Microsoft will actually allow Silverlight to run on more non-x86 platforms - specifically ARM, which dominates mobile computing. In the PC world, Silverlight can talk to PowerPC in addition to x86 to run on Windows and Linux.

Also, there's the issue of application ubiquity - the Nirvana of the fragmented handset market. As a downloadable runtime, Silverlight can potentially run on a large number of devices by providing a consistent interface and set of APIs. That would mean Silverlight applications also run on a greater number of phones than is possible with the current Windows Mobile, which is pulled and pushed to work on different handset hardware and that relies on OEMs to ship it into the market.

With Silverlight 4, which is already in beta, there are signs that when it comes to the PC Microsoft is starting to tailor its player to machines running Windows. It's doing that using Internet Explorer and COM.

Already, Windows Phone 7 devices are displaying signs of lock-in - only at a hardware level, as phones will feature a back and a Bing button. The question is how far features like these tie into Silverlight and constrain the ability of applications written for Silverlight to run on different handsets without the need for modification by the developer.

Finally, as in most important matters, there's the matter of size: Silverlight is a 5MB download that takes up to 10 seconds. That's still too big and too slow for mobile, something even Microsoft noted ruefully when it released the Silverlight 4 beta last November.

Silverlight as a platform for native applications on Windows mobile phones has plenty of appeal for the user and developers. The only thing standing in its way is Microsoft - and how far the company's willing to go.®