Commons talk:Categories

Spinning off new categoriesEdit

At what stage should a new category be spun off? Consider the following example. Suppose that I find the category "Public libraries in the United States" has become too large. That category could then be broken down into 51 sub-categories – one for each state (counting Washington DC as a state). Since the United States and Luxembourg are both sovereign independent states, should I also break the category "Public libraries in Luxembourg" down into a number of sub-categories – one for each administrative sub-division of Luxembourg. I think that the answer is "No", but why not? The real answer, I believe, lies in the size of the resultant categories.

May I suggest that a as a guideline well-defined category that contains fewer than 10 images should not be broken up, one that contain 100 images should be broken up while discretion should be used for a category with between 10 and 100 images. Martinvl (talk) 07:14, 31 March 2016 (UTC)

The concept is reasonable, but putting hard numbers to it is a mistake as that may be interpreted as "must do" not "consider doing". It depends on the situation - sometimes a large number in a single category is OK, but sometimes a much lower number is not tolerable.
Also bear in mind these concepts are not always straightforward subdivisions of one large concept. For instance if there are just 5 images in "Libraries in Luxembourg" there still might be a real need for "Libraries in Luxembourg City", because "Buildings in Luxembourg City" has hundreds of files.--Nilfanion (talk) 10:06, 31 March 2016 (UTC)
There is no hard and fast guidelines of when to break down categories. Sometimes it is useful to create a category with only one file in it. Also, just because you subdivide the libraries in the US does not mean you have to do the same in other countries. Also remember that most categories will get more photos with time, so they will need to be split up eventually anyways. --Sebari (talk) 22:35, 31 March 2016 (UTC)


Images often get categorized by date for no good reason, spamming date categories with irrelevant images. I propose that the text under categorization tips is supplemented. To the text that reads

"when?: when did the depicted events happen, or when was the image created? When was the image taken? This is especially important for historical images. An example would be Category:Warsaw in September 1939, Category:April 2010 in Northern Ireland"

could be added something like:

"Note, however, that categorizing by date is not appropriate for most images. A date-category should contain images that are typical for that time and place. Date-categories are not useful if they contain random events, and they easily become crowded if we use them often. We should ask ourselves what images somebody may expect if they look into a category." --Jonund (talk) 17:28, 13 May 2016 (UTC)

I am not a friend of date categories and hope that with the advent of Wikidata-like structured data Commons (in work), we can get rid of them. (In a few years.) That said, currently date categories serve two separate purposes: dating specific events and showing how something looked like in a general era. Personally, I like the current wording for that reason and am Symbol oppose vote.svg Oppose to changing it. --Sebari (talk) 19:47, 13 May 2016 (UTC)
That's exactly what these categories should be used for. The problem is that they are often cluttered with irrelevant images. A flower, a person, a logo, a bird are not interesting when you search by date. And a lot of motives may or may not be interesting. A building should be categorized according to date of construction, but usually they are categorized according to when the image was taken, and they look the same over long periods. A street view is often relevant, but if you have a lot of street views it would be proper with a selection. A rock concert is relevant if it is a well-known band, etc. Date-categories are often meaningful only when they describe a specific place or thing. --Jonund (talk) 08:46, 14 May 2016 (UTC)
In practice, the date categories do get flooded with photographs taken on that date. That is useful meta-data to record, and date categories are the only real way we have of doing so right now. If a high-level date category is swamped with photographs taken on that date - just split out the photographs - like how Category:April 2010 photographs is separated from Category:April 2010.
With regards to the examples you mention, the date can be somewhat significant to all those things. Its useful to know a picture of a flower was taken in April, its useful to know a portrait of a person was taken in 2009 etc. If your starting point is the date, you won't care for those files. But if your starting point is the subject, you may find the date useful to narrow down your search.--Nilfanion (talk) 09:03, 14 May 2016 (UTC)
I think it's better to have the date in the description field. In some cases (for instance large categories), subcategories by date are proper for portraits.--Jonund (talk) 18:00, 14 May 2016 (UTC)
The advantage of including the date as a category is it allows searching. If everything in Category:Albert Einstein is in date categories, it is much easier to use existing tools to find any photographs of him in 1945. If its just recorded in the description, its much harder to find things.--Nilfanion (talk) 12:31, 15 May 2016 (UTC)
How often does somebody need an image from a specific year? Most categories are small enough to find the right image easily, and the thumbnails usually give a hint of the approximate year. Large categories, however, may be fit for subcategories by date. (Besides, it's difficult to search by multiple categories.) I'm not advocating a prohibition of date-categories, only discouraging unnecessary and excessive use. --Jonund (talk) 16:04, 15 May 2016 (UTC)
Date categories can be very useful for intersections, such as those produced with catscan. As you say, when categories get large its natural to create sub-categories for <subject> in <date>, but that doesn't make it worthless to include date information when those subcats are not needed. Sure its not particularly high value (I don't add them to my own uploads), but its not incorrect to do so. Its probable that if you went around removing date categories en masse from things you don't see it as valuable on (such as flowers), you would probably get reverted and warned by multiple users. With that in mind I'd Symbol oppose vote.svg Oppose the change.
If you want to get a broader consensus, please raise this matter somewhere with higher traffic (such as the village pump).--Nilfanion (talk) 17:38, 15 May 2016 (UTC)
Return to the project page "Categories".