Currently there is no way to specify language when using our XmlaDataProvider but we have added such task to our todo list for implementation. I have updated your Telerik points for spotting this limitation.
I am afraid that currently there is no easy way to visualize pivot data with our chart. As soon as we have something ready we will blog about it.
Regarding you question about data access, as long as you can provide a list of data elements to our LocalDataSourceProvider you should have no problem display any data that is suitable for pivoting. For example, you can easily connect to an SQL server using RIA Services
. If the structure of your data is unknown until you actually get it you could use ICustomTypeProvider to creaate object with properties that are created dynamically. You might want to check out the following blog post which illustrate how ICustomTypeProvider can be used: Using ICustomTypeProvider in Silverlight 5 to Display JSON Data
and Using ICustomTypeProvider in Silverlight 5 beta with JSON and ASP.NET MVC 3
the Telerik team