Mikito Harakiri wrote:
>
> Well, "connect by" is [admittedly not especially elegant] way to
> express transitive closure. Now, are there any queries that can be
> expressed with "Recursive With" but not with transitive closure?
I think there are. It is known that on an ordered domain FO(TC) (first
order logic plus transitive closure) can express exactly all NSPACE[log
n] queries and FO(LFP) (first order logic plus a least fixpoint
operator) exactly all PTIME queries. The latter class is known to be
strictly greater than the first.
Received on Thu May 12 2005 - 17:45:23 CDT
