[NTG-context] Custom XML Export

I'm using ConTeXt's export to XML feature, but I'd like more control over the XML output. Is there a way to define a TeX command that will output a specific tag (<tag>content</tag>) around some text in the output? Ideally I'd like to write a completely custom XML printer; it would be very simple, but would allow me to define what tags I want for different things. Is there a way to change the behaviour of the existing one, or could you recommend a starting point for writing a new one? Many thanks, Toby