ROW features

I have implemented the ROW keyword, but am not sure that I've gotten
what the spec intends to be the full scope of functionality. It may be
that I've missed the main point completely :)

If someone has the time and interest I'd appreciate it if they would go
through the SQL99 spec and see what they deduce about the ROW keyword
and the underlying functionality which goes along with it. It seemed to
enable (at least) having an explicit keyword to introduce row clauses
(thus eliminating the ambiguity between a single-column row and a
parenthesized expression) and that is what I implemented. But I get
hints from reading the spec that there may be more involved, including
(perhaps) something like name/value pairs in a row expression.

afaict the spec is not at all verbose about this, and is very dense and
obtuse where it does discuss it. So more pairs of eyes would be greatly
appreciated...

- Thomas