In a structured tagging system, children should automatically receive the tag from parents as well.

Example:
Programming > JavaScript
Programming > Css

Anything tagged either js or css should automatically receive the appropriate parent tag.

Tags and folders

Tags are essentially virtual folders already

So, tags should have the option to be turned into 'primary tags' or folders via a checkmark

Any item can only contain one primary tag

All child/parent tags will be converted to primary tags (essentially making that trunk of the tree a folder trunk)

A parallel folder structure will be created for all the tags under which the files tagged with the tag will now live

If a file results in multiple primary tags after turning a tag into a primary tag either

• conflict has to be decided manually, and only selected primary tag is kept
• both tags will stay on item, it will exist in one directory as actual file, in one as symlink to actual file

Tags can be 'related' to one another not just through child/parent but sibling (or 'cousin') relationships, though i dont know how this wouldbe visualized / affect the structual tree