PresentationML
From Apache OpenOffice Wiki
PresentationML is the XML format used by Microsoft PowerPoint 2007 and that is part of the Office Open XML specification. It defines all the structure for the presentation related data. Pure graphic data (ie the content of the slide) is described using DrawingML.
Finding sample files
Use google and look for "download pptx".
Code organisation
oox/source/ppt/ contain the PresentationML specific code for the importer.
oox/source/drawingml is for DrawingML.