First things first: WTF is DII??? It's the "Document Interoperability Initiative" that Microsoft launched. The workshop will be a day filled with presentations from a variety of people, including members of the Office product groups at Microsoft and developers and consultants from several other companies (basically like the one held in Redmond a few weeks ago).
Together with Julien Chable, I'll be doing a talk on "Document Interop from an Open Source perspective - PHPExcel and OPENXML4J". Both our open-source products PHPExcel and OPENXML4J will be highlighted with some background and technical demos. We will prove that OpenXML documents provide interoperability between platforms (Windows / Linux) and technologies (.NET, PHP and Java).
Hope to see you there next tuesday!