According to http://blogs.zdnet.com/microsoft/?p=1159:
A handful of Microsoft’s top developers are working to create a new programming language, code-named “D,” which will be at the heart of the Microsoft’s push toward more intuitive software modeling.
D is a key component of Microsoft’s Oslo software-oriented architecture (SOA) technology and strategy. Microsoft outlined in vague terms its plans and goals for Oslo in late fall 2007, hinting that the company had a new modeling language in the works, but offering no details on what it was or when the final version would be delivered.
D will be a declarative language aimed at non-developers, and will be based on eXtensible Application Markup Language (XAML), sources, who asked not to be named, said.
Sources close to Microsoft confirmed the existence of D, which they described as a forthcoming “textual modeling language.” In addition to D, sources said, Microsoft also is readying a comlementary editing tool, code-namd “Intellipad,” that will allow developers to create content for the Oslo repository under development by Microsoft.