'Xen' programming language unites C#, XML and SQL programming languages. ""I am currently working on language and type-system support for bridging the worlds of object-oriented (CLR), relational (SQL), and hierarchical (XML) data, and of course first class functions," explains Mejer."
Mejer's paper, Unifying Tables, Objects, and Documents explains this idea more fully. Beware the Haskell programmer. Some of the syntax reminded me of Groovy. ExtremeTech also have an article.