One of Microsoft’s biggest selling points for its cloud platform is that developers can use .Net, Visual Studio and other programming tools they already know to write Azure applications.

But that’s not the end of the story. Microsoft researchers are working on a next-gen cloud programming model and associated tools. As those who’ve downloaded the Microsoft codename tracker I update each month know, something codenamed “Orleans” was beleived to be Microsoft’s cloud programming model. But it’s only recently that I’ve found more details about what Orleans is and how it is evolving.

Blogger and cloud expert Roger Jennings was the one who first tipped me to the Orleans codename. Back in February 2009, he discovered a reference to the Orleans software platform, which described it as “a new software platform that runs on Microsoft’s Windows Azure system and provides the abstractions, programming languages, and tools that make it easier to build cloud services.”

So what is Orleans, exactly? Orleans is a new programming model designed to raise the level of abstraction above Microsoft’s Common Language Runtime (CLR). Orleans introduces the concept of “grains” as being units of computation and data storage that can migrate between datacenters. Orleans also will include its own runtime that will handle replication, persistence and consistency. The idea is to create a single programming model that will work on clients and servers, which will simplify debugging and improve code mobility.

Here are a few slides from a recent Microsoft Research presentation that describe the platform in more depth:

There are some interesting related references in these slides. “Volta,” mentioned in the first slide, was a Microsoft Live Labs project that disappeared with little explanation a couple of years ago. Volta was considered a competitor to the Google Web Toolkit and was designed to enable the creation of distributed applications. There’s also something called “DC#” in the third slide. I’m wondering if this might be “Distributed C#.) Any other guesses?

One of the leaders of the Orleans work seems to be Jim Larus, who previously worked on Microsoft Research’s Singularity micokernel operating system. These days, Larus is Director of Research and Strategy for Microsoft’s eXtreme Computing Group, which the company established “to push the boundaries of computing.” One of the places computing’s boundaries are being pushed the furthest is in the cloud, where vendors are racing to make their datacenters bigger, faster, greener and more performant.

There is no mention in any of the new materials I found as to Microsoft’s planned schedule for Orleans. I can’t even tell if Orleans exists as a research prototype or is simply slideware at this point. Maybe we’ll hear more about it at Microsoft’s upcoming cloud-focused Professional Developers Conference in late October… Meanwhile, if anyone has any more Orleans information, whether it be real details or guesses, let’s hear it.