It is possible to extend xml-psychiatrist to do things I never anticipated. I've tried to make sure that the standard matchers do everything that you could reasonably hope to do, but I can't be sure of that. Therefore, you can create new matchers if you so desire. This section documents how to make new matchers.
All matchers are subclasses of the matcher class (see 4.1). The main work is done in the match method:
match matcher node matched-p
node--an xmls node.
matched-p--a boolean specifying whether or not matcher matched node.
You can get examples of matchers by looking at the source code.