Brion and Trevor just wrote up design documents you want to see:

http://www.mediawiki.org/wiki/Visual_editor/software_design "This document specifies the information models and technologies required to interact with Wikitext visually.... [t]his project, like this document, is in a research and design phase." Covers:

* Project status * Objectives * Constraints * Normalization * Document model ** Elements ** Blocks ** Content * Transactions ** Block transactions ** Document transactions ** Wiki transactions * Wikitext Representations * Linear Addressability

http://www.mediawiki.org/wiki/Wikitext_parser/Stage_1:_Formal_grammar discussing low-level tokens and structures:

* Tightly-bound tags * Brace structures * Loose structures * Line type tokens * Free/magic markup * Character references * Raw characters

http://www.mediawiki.org/wiki/Wikitext_parser/Stage_2:_Informal_grammar discussing loose structure assembly and separate nesting levels

Thanks, guys!