Can anyone point to examples of forms that require one or the other of
something? For instance, a contact form where either email -or- phone
is required. The context is I have a web app that has search fields
in which some combination of elements is needed. There could be as
many as a dozen different search criteria, and out of those there are
up to four "primary" fields and only one of which needs to be filled
in (doesnt matter which one, they have equal weight).