intro text:
- what it is
- what it isn't
- in what elements it's used
- what content is valid, if simple

sections:
- content: Content
- attributes: Attributes
- examples: Examples
- best: Best Practices
- design: Design Notes
- processing: Processing Expectations
- html: Comparison to HTML
- docbook: Comparison to DocBook

display environments:
- rich display
- terminal
- print
- aural
