Which Pointer Model?
The OAC model seems to propose, for HTML, an ID-based scheme (OAC Presentation, Slide 19), XPointers for XML, lines for raw text and, finally, the usual pixel-based rectangle for 2-dimensional targets:
Our own proposal, based on the Adobe Digital Edition schema (and as adopted by Mantano) uses the XPointer shorthand notation for HTML:
There is definitely room for improvement (and for a discussion) here. Our goal should be to present a unified method which encompasses video and audio content, too.