After adding couple of items in the collections we decided that we want only basic/simple Dublin Core metadata element set with 15 elements. I've deactivated and than also uninstall Dublin Core Extended plugin, but items are still described with extended metadata set, as you can see here http://www.cacak-dis.rs/kolekcije/items/show/4
I've also tried with modifying code, but it doesn't work.
Just to add that we are using Omeka version 1.0beta
This is unusual, but it is not a bug, at least in terms of the plugin. It's expected behavior to retain the extended Dublin Core terms after disabling the plugin. But it is true that uninstalling the plugin after it has been disabled should delete the metadata.
Rather, this may be a bug in our overall plugin functionality. I wrote a ticket, here: https://omeka.org/trac/ticket/832
For now, try this: re-activate the plugin and uninstall it while it is active.
Thanks, re-activating and than uninstalling the active plugin erased related metadata.