Bottom Level Data
  Raw Characters (8bits)
  Raw Graphics (Future)
  Raw Bits (Future)
  Pointers to Raw character, graphics, or bits. (32 bits)
  Index into raw (n-tuple)

Actual datatype definitions are in src/data.h

There is an inheritance hierarchy of what can point at what.
  Proper subset relation
  Example 
	Document
	 Chapter
	  Section
	   Paragraph
	    Text
  Or
	Document
	 Text
  Never
	Text
	 Chapter

Possible types
  See Scribe
  Document
  Text
  Chapter
  Sentence
  Display list?

Display indexes into various parts of the document, and into various
other sub-documents.

Page binding is upon display.

Propagation
  Efficiently knows when to stop
  Propagates macroscopic changes
    Moving paragraphs
  Propagates microscopic changes
    Correcting the spelling of a word  (perhaps by sharing text?)