User:Adelas/Category discussion
In the graphic below, I have created a fake category system that has toys sorted by color and by texture. Within color, there are subcategories for primary and secondary colors; and within the primary colors, there are red and blue things. (I didn't add any more secondary colors for space reasons)
The important item is the Red & Blue ball.
Technically, the Red & Blue ball is is neither all-red nor all-blue. It has a little of the aspects of both color categories, but doesn't fit neatly into either. If you feel that it absolutely HAS to go into the bottom-most category EVERY time, you will end up putting it in both categories Red and Blue, and someone looking for entirely blue things will be incorrectly told that the Red & Blue ball is a blue thing.
It also doesn't need a special Red and Blue category of its own, because if just put it into THE LOWEST CATEGORY INTO WHICH IT APPROPRIATELY FITS, then you can appropriately put the Red & Blue ball into the Primary Colors category. It's not in the lowest category of all, but it's in the lowest one that it properly fits within.
Furthermore, the goal is to specifically put the item in as few categories as possible.
In the second option above, the red train and red ball are included in the Red category, which is included in the Primary Colors category, which is in the By Color category, and of course within Items. It is within those higher-level categories already, BECAUSE the lower categories are inside the higher categories.
If each item is placed in EVERY category that applies to it (see image below), you end up with a HUGE amount of manual entering of categories.... and manual changing of categories if that is needed. If Red Train is removed from your list, in the example above, it only needs to be removed from two places: Red and Smooth, and then it's automatically out of Primary, Color, and Item. However, in the example below, it would need to be manually removed from every single one of those categories.
That's not such a big task when you're talking about a database with seven items in it, but with the thousands of pages on this wiki, and the amount of changes we see at each update, this can be a big problem.
Sometimes multiple categories aren't avoidable: Having an item in multiple categories is only a problem if they're redundant categories or closely connected in the same branch of the category tree.
In the examples above, no matter where the Red and Blue ball is in the color part of the tree, its texture is not being recorded there, and if it's important to sort the items by texture, the Red & Blue ball needs to have a second category over in the texture area of the tree. We don't consider that to be a redundant, unnecessary second category, because it's a completely different branch from the colors.