On Fri, Jul 08, 2005 at 10:03:57 -0400, Darren Alcorn <dalcorn@gmail.com> wrote:
> Here is a link that has a description. There is also a lot of
> examples (of syntax as well) on Oracle's website.
>
> http://www-db.stanford.edu/~ullman/fcdb/oracle/or-objects.html#nested
So they are permitting sets as a data type and then proceed to use a
misleading example (polygons are ordered sets of points).
Postgres already provides mechanisms to do the same thing using custom
datatypes. What it looks like they provide in addition is efficient(?)
relational (i.e. set) operators and foreign key constraints.