need info about extensibility in other databases

Hi there,

after we have GiST with concurrency and recovery support
(thanks to PosGIS community for support) I'd trying to 
find info about level of extensibility support in 
other major RDBMS's like Relational Extenders of DB2, 
Cartridges in Oracle and (?) in MS SQL.

With current GiST one could develope new datatype, index access methods and
queries and everything will have automatically concurency and recovery
support. New datatype could be not just a subset of existing types, but
completely new.

What's about other RDBMS ?

btw, "GiST programming tutorial" is available in Russian,
http://www.sai.msu.su/~megera/postgres/talks/gist_tutorial.html
    Regards,        Oleg
_____________________________________________________________
Oleg Bartunov, sci.researcher, hostmaster of AstroNet,
Sternberg Astronomical Institute, Moscow University (Russia)
Internet: oleg@sai.msu.su, http://www.sai.msu.su/~megera/
phone: +007(095)939-16-83, +007(095)939-23-83