• let users view maps with (hopefully any desired) sort
  and filter criteria
• let users rate every possible aspect of a map
• have an interface between users and the server, so that
  the server can take into account if a map is playable (maybe
  for a certain mode) or not, or how many spawn points are
  in the map etc.

CREATE TABLE `t_tags` (
  `filename` varchar(255) CHARACTER SET ascii COLLATE ascii_bin NOT NULL,
  `tag` varchar(255) CHARACTER SET ascii COLLATE ascii_bin NOT NULL,
  `tagvalue` mediumtext COLLATE utf8_bin NOT NULL,
  `note` mediumtext COLLATE utf8_bin,
  `user` varchar(255) CHARACTER SET ascii COLLATE ascii_bin NOT NULL,
  `timestamp` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  PRIMARY KEY (`filename`,`tag`,`tagvalue`(78),`user`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_bin

1. The table is not necessarily final -- if you see any problems with
   it, please tell me!
   .
2. mediumtext = VARCHAR(65535).
   .
   I somewhere read that mediumtext is is stored externally,
   in the file system. I don't know if that is good performance-wise
   -- and I don't know if that matters at all, regarding the relatively
   few entries this database has to handle (250 maps at first, then
   maybe growing to max. 1,000 or something). Where is the limit
   for in-database-storage and external storage? Is it 255 chars?
   Then I'm gonna leave it this way, because 255 is definitely too
   small. This is not SMS or twitter. =)
   .
3. tagvalue(78): primary key can be 1,000 chars max, and
   with an UTF8 char taking up up to 3 chars, there were only
   78 chars left.
   .
4. Why does "SHOW CREATE TABLE" show a single create
   statement incl. "PRIMARY KEY"? I thought composite
   primary keys had to be added after the create statement?
   But I'm not sure about that.
   .
5. The default engine is MyISAM, but I'm not sure about the
   implications of picking a certain engine. What I would like
   to have is something (probably) transaction based.
   Reason: I want to be able to cancel the last N actions
   (editing, creating, deleting, ...) of user $BADUSER. Do you
   think that is possible? And which engine would I need for
   that? InnoDB?

CREATE TABLE `t_taginfo` (
  `tag` varchar(255) CHARACTER SET ascii COLLATE ascii_bin NOT NULL,
  `format` tinyint(3) NOT NULL,
  `description` mediumtext COLLATE utf8_bin NOT NULL,
  PRIMARY KEY (`tag`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_bin