This post will focus on the data model used by this type of application. We need to understand how data is modeled if we plan to architect a cloud-based back-end.
The next few screens will talk a lot about SampleDataGroup and SampleDataItem objects. These are the core data objects used by a Windows 8 Metro Grid Application.
I thought this an awesome introduction to the XAML Metro Grid App project template, specifically how the data works. If you've created a test app off that template but are not really sure where to start or are thinking about doing so, this is a must read article.