Microsoft on its Windows Dev Center posted a design case study that compares and contrasts iPad app development with Windows 8 Metro-style app development.
"In this case study we want to help designers and developers who are familiar with iOS to reimagine their apps using Metro style design principles. We show you how to translate common user interface and experience patterns found in iPad apps to Windows 8 Metro style apps. We draw on our experience building the same app for the iPad and for Windows 8. We use common design and development scenarios to show how to leverage the Windows 8 platform and incorporate Metro style design principles," the case study explains.
The case study isn't a how-to, and is more of a visual comparison, showing how an iOS-based photo journal app works and looks on the iPad as compared to a Windows 8 tablet.
The article focuses on the differences in layout and navigation; commands and actions; orientation and views; notifications; and touch gestures.
The article also touches on contracts. A Windows 8 contract, as Microsoft describes it, "is like an agreement between Windows and one or more apps. Contracts define the requirements that apps must meet to participate in these unique Windows interactions." Developers of Metro-style apps -- a k a WinRT-based apps -- are encouraged to make use of these contracts.
Metro style apps use contracts and extensions to declare the interactions that they support with other apps and with Windows. Microsoft in its "App contracts and extensions" documentation describe the app contracts and extensions that Windows 8 Consumer Preview supports:
"App to app picking: Designed to "help users pick files from one app directly from within another app"
Play To: Helps users play digital media to connected DLNA devices from within an app
Search: Adds a search pane to an app "so users can search not only your app's content but content from other apps as well," according to Microsoft's description. "Users can also transfer the search query itself to other apps."
Settings: Provides in-context access to settings that affect the user's experience with an app
Share: Meant to help users share content from your app with another app or service, and vice versa. "Participating in the Share contract means that you don't have to write extra code or provide other developers with an SDK for your app just to share content," Microsoft explained.
You can read the full Design case study: iPad to Windows 8 Metro style app here