Ability to navigate within sub-components of documents containing specialized content
examples: math, music, genomic or chemical markup
Why an Expert Handler?
1. AT doesn't know how to deal with specialized content directly;
2. specialized components have content which needs to receive focus at different levels of granularity; for example a numerator within a numerator, an expression, a term, a bar of music, etc.
Each level of granularity needs to be able to provide the AT commands to inspect and navigate to and from "items" -- by word, bar, expression, clause, term, etc. -- depending upon the type of content being expressed.
Three system components need to interact:
1) the user agent or editor,
2) the AT, and
3) the expert handler