Open XML is an open ECMA 376 standard and is also approved as the ISO/IEC 29500 standard that defines a set of XML schemas for representing spreadsheets, charts, presentations, and word processing documents. Microsoft Office Word® 2007, Microsoft Office Excel® 2007, and Microsoft Office PowerPoint® 2007 all use Open XML as the default file format.
The Open XML file formats are useful for developers because they use an open standard and are based on well-known technologies: ZIP and XML.
The Open XML Format SDK 2.0 is built on top of the System.IO.Packaging API and provides strongly typed part classes to manipulate Open XML documents. The SDK also uses the .NET Framework Language-Integrated Query (LINQ) technology to provide strongly typed object access to the XML content inside the parts of Open XML documents.
Open XML Format SDK 2.0