Document Tags and Tag Groups

Hi Folks,

I'm trying to utilize tags to filter search results like it is described in this article.

My problem is that document could be assigned to one tags group only, but I'd like to have tags from a several groups, e.g. brand, type, etc.

If you'll check database structure, you'll figure out that the relation is not document -> tag group -> tags, but document -> group and document -> tags. With this structure it looks like tags group could be omitted and this is, actually, what I've tried to do.

I've added DocumentTags field to the form tab, as it is described in documentation, but the result has disappointed me: in case there is no tags group specified for particular document - tags selectors comes up blank, or if I just type in my tags, they are added to the DocumentTags field in CMS_Document table, but no records added to the CMS_Tag table; and if there is some tags group specified for the document I'm allowed to select (or add new) tags only within that tags group.

So the question is: does anyone have an idea how I can add tags from different tag groups to the one document?

Thanks in advance!