The foundation for XPS (OpenXPS), OOXML and a number of other formats is a common ZIP-based container. This container is defined by the Open Packaging Conventions and is standardized in ISO/IEC 29500-2 and ECMA 376-2. (We often refer to Open Packaging Conventions as OPC, or just ‘packaging’.)

Want to learn more? The packaging team are now blogging: you’ll find them at http://blogs.msdn.com/opc/