Cardinality of inputs

Right now, we have support for 1 or 0-or-more documents as input.
What's missing is support for 1-or-more and 0-or-1.

I can think of some reasons for 0-or-1 (an optional configuration
input, for example), but I can't think of any uses for 1-or-more.

But we don't have any atomic steps which need the missing options, so
we're considering a change that would only be used by some future (or
extension) atomic steps or by pipeline authors.

For pipeline authors, it seems that you'd have to handle the
optionality anyway, so handling the case of more than 1 when you
expected 0 or 1 wouldn't be a burden.

Absent more compelling arguments for changing the status quo, I don't
think any change is likely to be made.

If we do make a change, there was clear sympathy for a position which
says that neither of the two existing cases should be made more
difficult. That is, exactly 1 should be the default and 0-or-more
should require at most one attribute.

With that in mind, does anyone want to advance arguments for change
in this part of the spec?

                                        Be seeing you,
                                          norm

-- 
Norman Walsh <ndw@nwalsh.com> | Everything should be made as simple as
http://nwalsh.com/            | possible, but no simpler.