FIXME: Needs work
XML parsing components. The names of most of the files use the convention _.
may be parse - actions are performed during the parse walk - an XML tree is created first, then actions are pe4formed during a tree walk.
may be doc - the entire document is parsed while inherited actions are performed echo - the action is to output the original XML input tree - the action is to build an XML tree and return it schema - Output the Rust code for a schema