hi everyone,
i need to take advise about making decision upon the following..

We currently use two databases, the HSQLDB and MS Access.

HSQLDB Database(http://hsqldb.org/):
- accessed with Java
- we don't know how to access it in Python
- bulky storage format
- version upgrade frequently cause backwards compatibility problems
- multiple files sometimes cause confusion

MS Access Database:
- accessed with Visual Basic
- somewhat oversized file format
- Windows only

We are looking at a new database package to replace the MS Access database, and possibly the HSQLDB database as well. Possible options are below:

Postgres
PostGIS (location database only)
MySQL
SQLite

We want to be able to access the database using Python or Java, though Python is the first priority for testing. To explore the candidates, it would be best to install and test the packages using a small Python program that does the following:

1) Creates a new database
2) Adds data to the database
3) Changes data in the database
4) Queries the database
5) works on Windows and Linux
6)With PostGIS, we are interested in free software for visualizing and manipulating our data from the database. For example, if we could perform interpolation from a digital elevation model, and view plots with contours, this could be advantageous.

Please suggest me which open source database could be the best possible selection among those listed above..

Thanks in advance.