getting close...
i did more work on the exyus engine today. focused on cleaning up the caching experience. first, i cut about 20 lines of code out of each implementation class (SqlXmlHandler, XmlPageHander, XmlTemplateHandler, HtmlPostHandler, XmlFileHandler, GetHandler). that's because i was able to take repetitive code and factor it into a single routine. nice stuff.
second, i found that moving the MediaTypes collection from an instance array into metadata (custom attribute in C#) worked really well - except for one case. in a few classes, i just allow the default content type to rule things. that means i make to declarations when getting an instance of the resource class. this also means i haven't been adding a MediaTypes attribute to these classes - bad idea.
looks like i need to always has this on the class. that makes sense as it will be needed for the ClearCache routine as well. i can deal with that tomorrow.