Microsoft has released a preview of it LINQ to XSD technology. Like LINQ to XML, this provides query capabilities for XML documents. The difference here is that while LINQ to XML works over arbitrary XML in a late-bound fashion, LINQ to XSD is strongly typed.
The documentation, available separately, has a lengthy discussion on the design of the tool with a focus on the validation rules.
In traditional Microsoft fashion, tools are integrated into Visual Studio to generate the XSD-compatible types.
Unlike LINQ to XML, LINQ to XSD is not planned for the Orcas release. It is still in the early stages and Microsoft's XML Team is soliciting feedback.
LINQ to XSD requires the May LINQ CTP.