Wikipedia:Categories, lists, and series boxes

Wikipedia offers five ways to create groupings of articles, and this guideline deals with three of those: categories, lists, and article series boxes. Each way has advantages and disadvantages, and one or more of these ways may be appropriate in a given circumstance. (The other two methods are: See also sections and Navigational templates).

These methods should not be considered to be in competition with each other. Rather, they are synergistic, each one complementing the other. For example, since editors differ in style, some favor building lists while others favor building categories, allowing links to be gathered in two different ways, with lists often leapfrogging categories, and vice versa. One should not be deleted in favor of the other. Instead, each should be used to update the other. This provides two core methods of navigating Wikipedia. See the navigation menu at the top of Contents. The "category camp" shouldn't dismantle Wikipedia's list-based navigation system, and the "list camp" shouldn't tear down Wikipedia's category system.

Because of this, increasingly, multiple entries to fields of knowledge are provided. Take "symphonies", for example:
 * Categories: Category:Symphonies
 * Lists: List of symphonies by name
 * Templates: template:Symphonies by number and name

Below is a comparison of how these techniques group information...

Categories
Example of a category page. Every page in the article namespace should have at least one category. Categories should be on major topics that are likely to be useful to someone reading the article.


 * Article: Michael Jackson
 * Useful category: Category:American pop singers
 * Not useful: Category:Musicians whose first name starts with M

A category is probably inappropriate if the answer to the following questions is "no":
 * Is it possible to write a few paragraphs or more on the subject of a category, explaining it?
 * If you go to the article from the category, will it be obvious why it's there? Is the category subject prominently discussed in the article?

An article will often be in several categories. Restraint should be used, however &mdash; categories become less effective the more there are on a given article.

An article should usually not be in both a category and its subcategory, e.g. Microsoft Office is in Category:Microsoft software, so should not also be in Category:Software &mdash; except when the article defines a category as well as being in a higher category, e.g. Ohio is in both Category:U.S. states and Category:Ohio. (A good way to understand this exception is that if an article exists, and then a category is created on the same subject as the article, it should not cause the article to be removed from any of its categories.)

Exceptions should also be considered when the article subject has a relevance to the parent category that is not expressed by the subcategory's definition. For instance, if Category:Guillotined French Revolution figures was the only subcategory of Category:French Revolution figures, it would not make sense to remove major figures of the French Revolution solely because of the means of their death.

Categories appear without annotations, so be careful of neutral point of view (NPOV) when creating or filling categories. Unless it is self-evident and uncontroversial that something belongs in a category, it should not be put into a category. Especially see Categorization of people.

An exception to the above rules is Category:Wikipedia maintenance, which contains categories intended to be temporary.

Every category should be a subcategory of some other category. You can start from the top of the category hierarchy at Category:Fundamental. If you think a good parent probably exists but you just can't find it, add your new category to Category:Orphaned categories.

For articles without any stable category, the Uncategorized tag can be used to bring attention to it, either on its own, or in the format (Example: )  There is also an automatically updated list at Special:Uncategorizedpages which displays uncategorized/stubbed articles; however it only updates once every few days, and only lists 1000 articles at a time. So it is always best to explicitly place an uncat tag, if you are uncertain how an article should be categorized.

Advantages of categories

 * 1) Auto-linking. Create a link to a category on an article page, and a corresponding link to that article will be visible on the category page.
 * 2) Multi-directional navigation. A category can contain multiple subcategories, and can also be part of several categories. Categories are organized within Wikipedia into a web of knowledge starting with Category:Categories.
 * 3) Categories are good for exploratory browsing of Wikipedia.
 * 4) They are less susceptible to external linkspam than other types of pages, because only Wikipedia articles can be members of categories.

Disadvantages of categories

 * 1) Categories impose additional load on the servers, because they can't be served from the cache.
 * 2) Category entries are arranged in alphabetical order only (though you can control the alphabetization). They cannot be organized into sections and subsections on a single page, each with it's own descriptive introduction.
 * 3) Categories are difficult to maintain:
 * 4) A category with hundreds of items cannot be moved except by editing hundreds of articles.
 * 5) Tracking changes to a category is effectively impossible:
 * 6) A category's edit history does not show when entries were added or removed from the category.  So there is no easy way to tell when an article is removed from a category - it simply disappears with no indication that it was ever there in the first place.
 * 7) Wikipedia's watchlist feature is useless for tracking changes to a category's membership, because those do not show up as edits to the page (because they don't even exist on that page -- they're at the bottom of each member page).
 * 8) Categories cannot contain invisible links (such as to talk pages), which cause edits to those pages to appear when the user clicks on "related changes".  (Thus:    )
 * 9) Categories do not support other forms of tracking, such as adding red links.  (Red links are useful as gap indicators and as task reminders to create those articles).
 * 10) Categories give no context for any specific entry, nor any elaboration; only the name of the article is given.  That is, listings cannot be annotated (with descriptions nor comments), nor referenced.
 * 11) Categories are not operational on most mirror sites.
 * 12) Alternative names for the same item can be included only by including redirects in the category.
 * 13) It is not obvious to new users that categories exist, how to add items to them, how to link new categories into existing schemes, nor point of view (POV) concerns.

Lists
Example of a list. Lists make one exception to policies and guidelines applicable to all main or article namespace pages: lists are self-referential by their very nature (the word "list" or "lists" in their titles refers to an entity on Wikipedia, not in the world-at-large), and therefore they are an exception to the Avoid self-references guideline.

Advantages of lists

 * 1) Lists are good for exploratory browsing of Wikipedia, and provide a useful alternative to the cumbersome category system - lists are often more comprehensive because each is maintained from a centralized location (at the page itself). See the top end of the list hierarchy at Lists of topics, Lists of basic topics, List of overviews, and List of glossaries.
 * 2) Lists are much easier to build (fill) than categories, because entries can be gathered, cut and pasted in from searches and other sources.  Brainstorming entries from one's personal education is much easier, because you don't have to hunt for the articles to place the tags on, you simply type the topics into the list.
 * 3) Lists can be embellished with annotations (further details). For example, a list of soccer world championship teams can include with each entry when each championship was won, who the champions defeated, who their coach was, etc.
 * 4) Lists can be referenced to justify the inclusion of listed articles.
 * 5) Lists can include items for which there are yet no articles (red links).
 * 6) List items can be sorted using a variety of methods. An article can appear several times or in different ways in the same list.
 * 7) Lists can be linked to specific sections of articles.
 * 8) Lists can include invisible links to discussion pages, so that clicking on "related changes" will include those (Format:   ).
 * 9) Lists can be more easily edited by newbies who are less familiar with Wiki markup language.
 * 10) Images can be interspersed throughout a list.
 * 11) Lists can be formatted in many different ways, to improve the presentation of the contents of the list.
 * 12) Templates (such as navigation boxes) can be included as portions of a list.

Disadvantages of lists

 * 1) A lengthy list may make a Wikipedia article longer than its recommended size
 * 2) New users who are creating articles may be completely unaware of any related list which needs to be updated
 * 3) Lists, especially about careers, awards, or commercial products, are often targets for unsourced or self-promotional additions, including external linkspam.

Article series boxes
Example of an article series box. Article series boxes (or navigational templates) are boxes with links to other related articles. Examples include presidents of the United States, movies in the Friday the 13th Series, or Narnia books. They may be used for small and more or less complete sets. The importance of the subject matter is not a consideration.

A series should have some ordering, whether chronological or otherwise. Alphabetical order is not preferable, as categories naturally arrange articles alphabetically, making a series box redundant. It is not enough that it is possible to organize the elements of a series into a structure &mdash; that structure should itself be useful. For example, a box for characters from Buffy the Vampire Slayer by the order of listing in the opening credits is an ordering but is not useful, because it is unlikely that people would actually want to read the articles in that order. A category should be used instead.

As with categories, all the articles in a box should substantially deal with the subject of the box.


 * Is the subject of this box something that would be mentioned on every article in the series?
 * Is a given article in the series likely to mention the article before or after it in the series outside of the box?
 * Are the elements of the box all going to generate articles substantial enough that the box will not look like an unmanageable blight on an otherwise tidy computer monitor?

If the answer to any of these questions is "no", a category or list is probably more appropriate.

If an article has more than one series box, it may be appropriate to convert some or all to categories.

For very long series, it is preferable to use incumbent series, which only show the elements of the series immediately preceding and succeeding the article.

Related pages regarding templates:
 * Series templates
 * Navigational templates''
 * Article series boxes policy (proposed)
 * Template standardisation

Advantages of article series boxes

 * 1) Provide a consistent look and navigation system for related articles (though not between different topics &mdash; there is no standard format; though see Template standardisation).
 * 2) Faster to navigate than a category.
 * 3) Give immediate information to equivalent elements
 * 4) For presenting a series of articles in a  chronological order, series boxes are often most appropriate. Example: template:Princess Royal (there are two Marys and two Annes in that list, which makes the chronological way of presenting these princesses an asset to a merely alphabetically ordered presentation of these same names)

Disadvantages of article series boxes

 * 1) Simple boxes can often be replaced with a category. It also can be difficult to give more detail than a category can give without the box becoming unmanageably large.
 * 2) Article series boxes can become ugly or pointless, e.g. by unsightly coloring schemes, size, number of them on the same page, etc.  For this reason article series boxes need to be self-evident, while they can't contain much text for definitions or explanations.
 * 3) Often inadvertently push a POV and suggest that one aspect of a topic is more important than others, being used to advertise obscure topics in prominent places, or asserting project proprietorship. Many templates go to Templates for deletion because they appear to push POV. Trying to remedy this by adding more series boxes might lead to the disadvantage described in the previous point.
 * 4) Can alter the page lay-out without the reason thereof showing on the page itself (e.g. when the series box contains a NOTOC instruction, an unclosed div, etc.)
 * 5) Article series boxes work best as un-substed templates. However, this increases server load.