Thanks to both of you for your answers.
Actually my question had not so much to do with the files, but with a database that belongs to a plugin. Let's say I install a table in version 1.0.0 of the plugin. At some point I decide that I need another field in the table (version 1.0.1). The install therefore has to check if it has to add the whole table (I don't want to use the force option, because that would delete any data in the table) or if it only has to add the new field.
I will use the information in the config file to get the version and then add the necessary tables/fields.
Ivan
-----
Iyengar Yoga Resources /
GT Plugins