"This specification defines the OEBPS Container Format (OCF). OCF is a general-purpose container technology. This specification describes the general-purpose container technology in the context of encapsulating OEBPS publications and OPTIONAL alternate renditions thereof. It is however anticipated that the general-purpose container technology described herein will ultimately be used in other bundling applications."
So, what does that mean? Basically, that if you want to create a document in ePub format, you've got to follow this specification.
