Hm, "
hard
active"
datbases,
the
Rete, TREAT, and
LEAPS
algorithms, the old HiPAC,
VenusDB, and
Sentinel
projects. Interesting stuff, but yes, seemingly very little that's
usefull to RDBMS users in the real world. Most of the research papers
also seem to be old, not much in the last five years or so. It's not
clear whether anyone's working on this stuff at all right now.
It would be nice to have this kind of Rete-algorithm
capability in an RDBMS like Oracle or PostgreSQL. I don't know how
triggers are implemented in Oracle exactly, but they definitely are
not as sophisticated as rule-based systsms which use the Rete
algorithm. I ran into this back when I was implementing an online
bond trading site (which worked, but never even remotely approached
the size of the NYSE!).
I forget the exact error, but Oracle does not allow recursive
trigger execution. So, if you have programmed trades in the system,
and you execute one order which changes system information (like
"volume of this security traded today"), which could then cause
another trade to execute - you have a problem. One can imagine ways
to program around this limitation in Oracle, but a more general
solution for such scenarios may call for something like the
"coupling modes" introduced by HiPAC. At the time, our approach was
simply to Not Do That; we avoided adding any features that would cause
recursive trigger execution.
