I attended a Microsoft presentation last night on the new ADO.NET Entity Framework which was released on Monday (11 Aug 08) as part of VS 2008 SP1 and .NET Framework 3.5 SP1.
The essential idea is to allow developers to use LINQ to work against a conceptual model of the database instead of the physical model.
The Entity Framework uses two XML mappings
SSDL - Store Schema Definition Language (the physical schema)