Simple schema question

[Dan Shriver <dshriver@sharemedia.com>]

In specifing a schema is there a way to say an object MUST have
x or Y?

I know x and Y is:

MUST (x $ Y)

but is there an "OR" type construct that works on a set of
attributes?

Example: must (a,b,c and either d or e) may (f)

(MUST (a $ b $ c $ (d || e))
 MAY (f))