This is a beta version of the Excel 2010 XLL Software Development Kit (SDK). The SDK exposes all relevant Excel 2010 functionality to XLL add-in developers, and introduces two new "power UDF" capabilities – Asynchronous user-defined functions (UDF), and HPC function remoting.
You can expect an updated version of this SDK after the final release of Microsoft Office 2010. The purpose of the SDK is twofold:
- To make sure that all relevant Excel 2010 functionality is available to XLL add-in developers. This includes all new worksheet functions, and the ability to create 64-bit versions of XLL add-ins.
- To introduce two exciting new "power UDF" capabilities: Asynchronous UDFs; and remoting function calls to HPC (High-Performance Computing) clusters.
Asynchronous UDFs are exactly what they sound: you can create a user-defined function (UDF) which starts some asynchronous process (such as sending out a request) and immediately returns. Excel tracks the pending result. When the result becomes available, the add-in sends it back to Excel through a call-back function. This lets you send out many external requests at the same time, to be concurrently run on external resources.
In addition, if you have a High-Performance Computing cluster (aka a "grid"), you can register existing, synchronous functions as "cluster safe", and have Excel automatically send calls to them to be executed remotely and asynchronously on the cluster – without needing to rewrite the functions as asynchronous.