Jackie,
> I am interesting in PostGis and postgreSQL and want to do something on
> it. My idea is to build a Spatial Database Cache to accelerate GIS
> applications .So I want to ask you some question and hope to get your
> answer.
You should probably try the PostGIS mailing list:
http://postgis.refractions.net/mailman/listinfo/postgis-users
... I don't think that anyone here will be able to answer you.
--
Josh Berkus
PostgreSQL @ Sun
San Francisco