Tag
type: Class
comment: Tag is the keyword which users add to one object

Comment
type: Class
comment: Comment is what the tagger adds to the object or tag during the tagging

Source
type: Class
comment: Source is the place where the object is hosted. It can be delicious, flickr, youtube, etc.

Vote
type: Class
comment: Tagging can be viewed as voting. Vote can be the number of different taggers tagging a bookmark, a photo or a video as favoriate.

Date
type: Class
comment: Date is the time stamp o fte tagging behavior. Format is "MmmYY"

Tagger
type: Class
comment: Tagger is the user who tags object

Tagging
type: Class
comment: Tagging is the concept which is created to link other concepts. Itself does not have any real meaning

Object
type: Class
comment: object is the thing which tagger is tagging. It can be bookmarks, photos, videos, musics, books, slides, etc.