In Simile Exhibit is an attribute called ex:columnFormats. After googling for a while, the best list of valid values I can find is from Simile's wiki...
ex:columnFormats
list of format expressions
comma separated list of format expressions, e.g., "list, image, date { mode: short }"
...So, list, image, and date are valid. I've discovered that url is valid.
Where is it documented what the complete list is?
Wow... crickets... even got a tumbleweed badge for this one.
Does no one use Simile? Maybe that is a sign.