Now that the Open XML is an international standard, work continues on our contributions to make the it accessable to developers. No longer called Microsoft SDK for Office Open XML, the new SDK is called Open XML Format SDK to reflect that Microsoft is a contributor.
The April Connumity Technology Preview (CTP) can be downloaded from Open XML Format SDK. The final version is expected in June.
The Open XML Format SDK Technology Preview simplifies the task of manipulating Open XML packages. The Open XML Application Programming Interface (API) encapsulates many common tasks that developers perform on Open XML packages, so you can perform complex operations with just a few lines of code. Using this API, you can programmatically generate and manipulate Word 2007 documents, Excel 2007 spreadsheets, and PowerPoint 2007 presentations. The programming model uses managed code, so it's safe for server-side scenarios.
The Open XML API will release in two versions. Open XML API Version 1.0 is the updated version of the CTP in June 2007 and will only contain the Open XML Packaging API. Open XML API Version 2.0 will contain all of the Open XML API components, including the Open XML Packaging API with further updates. It will enforce validity of the content either in the original Open XML documents or being generated through this API. The purpose of this plan is to give out the long awaited Go-Live license of the existing Open XML Packaging API to external developers.
To find out more details about the SDK, see Erika Ehril's blog posting Announcing the Open XML Format SDK April CTP.