The current API for tags isn't optimal. Some operations are done in tag/lib.php, some in blog/lib.php, some in blocks/... This aims to clean up the current API, makit it easier to expend the tags functions in moodle.

I'm sending a first file, containing only documentation and prototypes. I'm trying to come up with something that does the job, but is as minimal as possible.

Missing from this file are:

• tag_selection_box(...): a function to display the "tag selection box", so that all forms display the same interface to the user (which is currently not the case: user interests and blog posts have different ways of getting tags)
• tag_get_links(...): a function to return the tags along with the html links to them
• ...?