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Every page in the article namespace should belong to at least one category. Categories should be major topics that are likely to be useful to someone reading the article.

Every page in the article namespace should belong to at least one category. Categories should be major topics that are likely to be useful to someone reading the article.

:'''Article:''' [[Michael Jackson]]

:'''Article:''' [[Directory:MyWikiBiz]]

:'''Useful category:''' [[:Category:Pop singers]]

:'''Useful category:''' [[:Category:Companies]]

:'''Not useful:''' ''Category:Musicians whose first name starts with M''

:'''Not useful:''' ''Category:Companies whose first name starts with M''

Questions to ask to determine whether it is appropriate to add an article to a category:

Questions to ask to determine whether it is appropriate to add an article to a category:

If the answer to either of these questions is no, then the category is probably inappropriate. Note that it is always appropriate to add articles to categories that fit into well established taxonomies. For example, every article about a musical album is categorized in some <nowiki>[[Category:Artistname albums]]</nowiki> category, which is in turn categorized in [[:Category:Albums by artist]].

If the answer to either of these questions is no, then the category is probably inappropriate. Note that it is always appropriate to add articles to categories that fit into well established taxonomies. For example, every article about a musical album is categorized in some <nowiki>[[Category:Artistname albums]]</nowiki> category, which is in turn categorized in [[:Category:Albums by artist]].

===Some general guidelines===

===Some general guidelines===

#Categories are mainly used to browse through similar articles. Make decisions about the structure of categories and subcategories that make it easy for users to browse through similar articles.  

#Categories are mainly used to browse through similar articles. Make decisions about the structure of categories and subcategories that make it easy for users to browse through similar articles.  

#An article will often be in several categories. Restraint should be used as categories become less effective the more there are on any given article.

#An article will often be in several categories. Restraint should be used as categories become less effective the more there are on any given article.

#Articles should not usually be in both a category and its subcategory. For example [[Golden Gate Bridge]] is in [[:Category:Suspension bridges]], so it should not also be in [[:Category:Bridges]]. However there are occasions when this guideline can and should be ignored. For example, [[Robert Duvall]] is in [[:Category:Film actors]] as well as its subcategory [[:Category:Best Actor Academy Award winners]]. See #5 for another exception. For more about this see '''[[Wikipedia:Categorization/Categories and subcategories]]'''

#Articles should not usually be in both a category and its subcategory. For example [[Golden Gate Bridge]] is in [[:Category:Suspension bridges]], so it should not also be in [[:Category:Bridges]]. However there are occasions when this guideline can and should be ignored. For example, [[Robert Duvall]] is in [[:Category:Film actors]] as well as its subcategory [[:Category:Best Actor Academy Award winners]]. See #5 for another exception. For more about this see '''[[Centiare:Categorization/Categories and subcategories]]'''

#Check to see where siblings of the article reside. If there are few if any articles in a category, the article probably belongs in one of the subcategories.

#Check to see where siblings of the article reside. If there are few if any articles in a category, the article probably belongs in one of the subcategories.

#Articles should be placed in categories with the same name. However, the article and the category do not have to be categorized the same way. The article can also be placed in categories populated with similar articles. The category can be put into categories populated with similar subcategories. For an example of this see [[George W. Bush]] and [[:Category:George W. Bush]].  

#Articles should be placed in categories with the same name. However, the article and the category do not have to be categorized the same way. The article can also be placed in categories populated with similar articles. The category can be put into categories populated with similar subcategories. For an example of this see [[George W. Bush]] and [[:Category:George W. Bush]].  

===Categories vs. Lists vs. Info boxes===

===Categories vs. Lists vs. Info boxes===

For alternative methods of grouping articles, and the circumstances in which they should be used, see [[Wikipedia:Categories, lists, and series boxes]].

For alternative methods of grouping articles, and the circumstances in which they should be used, see [[Centiare:Categories, lists, and series boxes]].

===Categories applied to articles on people===

===Categories applied to articles on people===

A separate wikipedia page [[Wikipedia:Categorization of people]] was created to help you in designing, applying and checking categories that are used for articles on people.

A separate Centiare page [[Centiare:Categorization of people]] was created to help you in designing, applying and checking categories that are used for articles on people.

===Categories do not form a tree===

===Categories do not form a tree===

Each Wikipedia article can appear in more than one category, and each category can appear in more than one parent category. Multiple categorization schemes co-exist simultaneously. In other words, categories do not form a strict hierarchy or [[tree structure]], but a more general [[directed acyclic graph]] (or close to it; see below).

Each Centiare article can appear in more than one category, and each category can appear in more than one parent category. Multiple categorization schemes co-exist simultaneously. In other words, categories do not form a strict hierarchy or [[tree structure]], but a more general [[directed acyclic graph]] (or close to it; see below).

Nevertheless, parts of the category graph will be tree-like, and it may be convenient to think of parts of the category graph as being like multiple overlapping trees. When applying the guidelines above, consider each tree to be independent of the overlapping trees. A person browsing through a hierarchy should find every article that belongs in that hierarchy. This can lead to a good deal of debate as to what the hierarchies actually are. To clarify the structure of the hierarchy and help people browse through it, you can add a classification to each category. For more about this, see [[Wikipedia:Classification]].

Nevertheless, parts of the category graph will be tree-like, and it may be convenient to think of parts of the category graph as being like multiple overlapping trees. When applying the guidelines above, consider each tree to be independent of the overlapping trees. A person browsing through a hierarchy should find every article that belongs in that hierarchy. This can lead to a good deal of debate as to what the hierarchies actually are. To clarify the structure of the hierarchy and help people browse through it, you can add a classification to each category. For more about this, see [[Centiare:Classification]].

===Cycles should usually be avoided===

===Cycles should usually be avoided===

Although the MediaWiki software does not prevent [[cycle (graph theory)|cycles]] (loops), these usually should be avoided. Cycles can be confusing to some readers, they can challenge some automated searching processes and they can grow quite large. For example, in January 2006 a 22-member category cycle was discovered and eliminated.  

Although the [[Directory:MediaWiki|MediaWiki]] software does not prevent [[cycle (graph theory)|cycles]] (loops), these usually should be avoided. Cycles can be confusing to some readers, they can challenge some automated searching processes and they can grow quite large. For example, in January 2006 a 22-member category cycle was discovered and eliminated.  

However, acceptable loops also exist. Self-referencing systems such as the [[meta-]] fields naturally create cycles that provide many examples. This type of cycle involves making a category one of its own subcategories. A real-world example of a self-referencing system is “education about education,” such as:

However, acceptable loops also exist. Self-referencing systems such as the [[meta-]] fields naturally create cycles that provide many examples. This type of cycle involves making a category one of its own subcategories. A real-world example of a self-referencing system is “education about education,” such as:

==How to put an article into categories==

==How to put an article into categories==

Adding an article to a category is as simple as editing the article and adding a link to the category. For instance, to add ''[[Felis silvestris catus]]'' article to the "fluffy creatures" category, you would edit the article and enter <tt><nowiki>[[Category:Fluffy creatures]]</nowiki></tt> at the bottom. The appeal of categories is that unlike lists, they update themselves automatically, and you don't have to edit the category to add an article to it. However, categories are not a substitute for [[Centiare:list|list]]s, and you will find that many articles belong to both lists and categories.  

Adding an article to a category is as simple as editing the article and adding a link to the category. For instance, to add ''[[Felis silvestris catus]]'' article to the "fluffy creatures" category, you would edit the article and enter <tt><nowiki>[[Category:Fluffy creatures]]</nowiki></tt> at the bottom, but ''before'' [[Wikipedia:Interlanguage links|interlanguage links]]. The appeal of categories is that unlike lists, they update themselves automatically, and you don't have to edit the category to add an article to it. However, categories are not a substitute for [[Wikipedia:list|list]]s, and you will find that many articles belong to both lists and categories.  

When adding an article to a category, or creating categories, one should be careful to use the correct categories and subcategories. Horizontal categorization, directly below, refers to placing an article in the correct category while vertical categorization refers to placing an article in the correct ''sub''category.

When adding an article to a category, or creating categories, one should be careful to use the correct categories and subcategories. Horizontal categorization, directly below, refers to placing an article in the correct category while vertical categorization refers to placing an article in the correct ''sub''category.

to find the most appropriate place.  

to find the most appropriate place.  

In the "vertical" dimension, Wikipedia has traditionally been more frugal, placing articles only in the most specific categories they reasonably fit in. Thus, if there is a [[:Category:American film actors]], [[John Wayne]] would go there and not in [[:Category:Film actors]] or [[:Category:American actors]]. However, there is a school of thought that argues that, because different users may be interested in different categories, and because placing articles in multiple categories takes up minimal additional space, in some cases one should place articles in all the categories that apply.  

In the "vertical" dimension, Centiare has traditionally been more frugal, placing articles only in the most specific categories they reasonably fit in. Thus, if there is a [[:Category:American film actors]], [[John Wayne]] would go there and not in [[:Category:Film actors]] or [[:Category:American actors]]. However, there is a school of thought that argues that, because different users may be interested in different categories, and because placing articles in multiple categories takes up minimal additional space, in some cases one should place articles in all the categories that apply.  

<!-- For example, [[Elizabeth_II_of_the_United_Kingdom|Queen Elizabeth]] should not be listed directly under People, but 'Category:Monarchs of the United Kingdom' might be a good place for her. We know that all Queens of the United Kingdom qualify as Famous Britons and as Royalty, and all of those folks qualify as People. Sometimes there's a good reason to assign an article to two categories, one of which is a direct or indirect subcategory of another. For a well-argued case study, see [[John Lennon]]. -->  

<!-- For example, [[Elizabeth_II_of_the_United_Kingdom|Queen Elizabeth]] should not be listed directly under People, but 'Category:Monarchs of the United Kingdom' might be a good place for her. We know that all Queens of the United Kingdom qualify as Famous Britons and as Royalty, and all of those folks qualify as People. Sometimes there's a good reason to assign an article to two categories, one of which is a direct or indirect subcategory of another. For a well-argued case study, see [[John Lennon]]. -->  

For more about this see '''[[Wikipedia:Categorization/Categories and subcategories]]'''

For more about this see '''[[Centiare:Categorization/Categories and subcategories]]'''

==How to create categories==

==How to create categories==

===Category naming===

===Category naming===

Categories follow the same general naming conventions as articles, for example do not capitalize regular nouns. For specific conventions related to categories, see [[Wikipedia:Naming conventions (categories)]].

Categories follow the same general naming conventions as articles, for example do not capitalize regular nouns. For specific conventions related to categories, see [[Centiare:Naming conventions (categories)]].

Whatever categories you add, make sure they do not implicitly violate

Whatever categories you add, make sure they do not implicitly violate

the [[WP:NPOV|neutral point of view policy]]. If the nature of something is in dispute (like whether or not it's fictional or scientific or whatever),

the [[Centiare:Main page|Main page]] [[NPOV|neutral point of view policy]]. If the nature of something is in dispute (like whether or not it's fictional or scientific or whatever),

you may want to avoid labelling it or mark the categorization as

you may want to avoid labelling it or mark the categorization as

disputed. Most categorizations are pretty straightforward, though.

disputed. Most categorizations are pretty straightforward, though.

== How to delete a category ==

== How to delete a category ==

Please refer to [[Wikipedia:Categories for discussion]]

Please refer to [[Centiare:Categories for discussion]]

== How to rename a category ==

== How to rename a category ==

Please refer to [[Wikipedia:Categories for discussion]]

Please refer to [[Centiare:Categories for discussion]]

==Organizing categories==

==Organizing categories==

==Other requirements==

==Other requirements==

===Wikipedia namespace===

===Centiare namespace===

Categories relating to the [[Wikipedia:project namespace|Wikipedia namespace]] should be added only to the [[Wikipedia:talk page|talk page]] of articles. For example, tags suggesting the article [[:Category:To do|needs work]] would be placed on the talk page as they are relevant to editors and not an aid to browsing in the way ordinary categories are.

Categories relating to the [[Centiare:project namespace|Centiare namespace]] should be added only to the [[Centiare:talk page|talk page]] of articles. For example, tags suggesting the article [[:Category:To do|needs work]] would be placed on the talk page as they are relevant to editors and not an aid to browsing in the way ordinary categories are.

===User namespace===

===User namespace===

Categories relating to the User namespace should be added only to Wikipedia-specific categories. Users should ''not'' add their user pages to article namespace categories such as [[:Category:People]] or other subcategories, [[:Category:Biologists]] etc, which are reserved for pages in the article namespace. However, it is appropriate to add a user page to ''Wikipedia-specific categories'' such as [[:Category:Wikipedians]] or other similar subcategories such as [[:Category:Wikipedian musicians]]. (See also [[m:Help:Category]] for guidelines on category "pollution").

Categories relating to the User namespace should be added only to Centiare-specific categories. Users should ''not'' add their user pages to article namespace categories such as [[:Category:People]] or other subcategories, [[:Category:Biologists]] etc, which are reserved for pages in the article namespace. However, it is appropriate to add a user page to ''Centiare-specific categories'' such as [[:Category:Centiare]] or other similar subcategories such as [[:Category:Centiare musicians]]. (See also [[Help:Category]] for guidelines on category "pollution").

If you copy an article to your user namespace (for example, as a temporary draft or in response to an [[Wikipedia:Edit war|edit war]]) you should decategorize it in one of the following ways, (where foobar is the category name):

If you copy an article to your user namespace (for example, as a temporary draft or in response to an [[Centiare:Edit war|edit war]]) you should decategorize it in one of the following ways, (where foobar is the category name):

#<nowiki>[[:Category:foobar]]</nowiki>, note the extra : before Category.

#<nowiki>[[:Category:foobar]]</nowiki>, note the extra : before Category.

#<nowiki>{{cl|foobar}}</nowiki>, see {{tl|cl}}

#<nowiki>{{cl|foobar}}</nowiki>, see {{tl|cl}}

#<nowiki>{{ccl|foobar}}</nowiki>, see {{tl|ccl}}

#<nowiki>{{ccl|foobar}}</nowiki>, see {{tl|ccl}}

#<nowiki>{{lcs|foobar}}</nowiki>, see {{tl|lcs}}

#<nowiki>{{lcs|foobar}}</nowiki>, see {{tl|lcs}}

===Keep cats out of the sandbox===

===Keep cats out of the sandbox===

Until these issues are addressed (in future versions of the software), '''#REDIRECT''' should not be added to category pages.

Until these issues are addressed (in future versions of the software), '''#REDIRECT''' should not be added to category pages.

"Soft" redirects for categories can be created using {{[[Template:Category redirect|Category redirect]]}}.  A [[Wikipedia:Bots|bot]] traverses categories redirected in this manner moving articles out of the redirected category into the target category, see [[Template talk:Category redirect]].

"Soft" redirects for categories can be created using {{[[Template:Category redirect|Category redirect]]}}.  A [[Centiare:Bots|bot]] traverses categories redirected in this manner moving articles out of the redirected category into the target category, see [[Template talk:Category redirect]].

===Category sorting===

===Category sorting===

* the logical sort order is not alphabetical (example: individual month articles in year categories such as [[:Category:2004]], using e.g. the sort key "*2004-04" for April).

* the logical sort order is not alphabetical (example: individual month articles in year categories such as [[:Category:2004]], using e.g. the sort key "*2004-04" for April).

Using this method to sort category entries is sometimes informally referred to as ''the pipe trick''. However, this use of the pipe character is very different from the original Wikimedia [[m:Help:Piped link#Automatic conversion of the wikitext (pipe trick)|pipe trick]] which allows one to easily hide parenthetical disambiguation in links.

Using this method to sort category entries is sometimes informally referred to as ''the pipe trick''. However, this use of the pipe character is very different from the original Centiare pipe trick which allows one to easily hide parenthetical disambiguation in links.

It is possible to force an article or subcategory to the top of the list by using a non-alphanumeric character as the first after the pipe. For example, using <tt><nowiki>[[Category:Ford| Ford Motor Company]]</nowiki></tt> (note the space) or <tt><nowiki>[[Category:Ford|*Ford Motor Company]]</nowiki></tt> would force that article to be displayed before all the others. Many editors feel that the space character produces the best aesthetic appearance when the category is displayed. Using a space or asterisk after the pipe is the customary way to categorize an article in a category with the same name, indicating that the article is the '''main topic article''' for that specific category. For an example, see [[:Category:Suspension bridges]]. Using {{tl|Catmore}} may be preferable - no consensus has been established yet. To list at the end (after z) of a category, the sort key ~ can be used <tt><nowiki>[[Category:Polyhedra|~Polyhedra templates]]</nowiki></tt>.

It is possible to force an article or subcategory to the top of the list by using a non-alphanumeric character as the first after the pipe. For example, using <tt><nowiki>[[Category:Ford| Ford Motor Company]]</nowiki></tt> (note the space) or <tt><nowiki>[[Category:Ford|*Ford Motor Company]]</nowiki></tt> would force that article to be displayed before all the others. Many editors feel that the space character produces the best aesthetic appearance when the category is displayed. Using a space or asterisk after the pipe is the customary way to categorize an article in a category with the same name, indicating that the article is the '''main topic article''' for that specific category. For an example, see [[:Category:Suspension bridges]]. Using {{tl|Catmore}} may be preferable - no consensus has been established yet. To list at the end (after z) of a category, the sort key ~ can be used <tt><nowiki>[[Category:Polyhedra|~Polyhedra templates]]</nowiki></tt>.

Other specifics:

Other specifics:

*For more detailed guidelines about sorting names of people, see [[Wikipedia:Categorization of people#Ordering names in a category]].

*For more detailed guidelines about sorting names of people, see [[Centiare:Categorization of people#Ordering names in a category]].

*Don't start the category sort key with a lower case letter, unless you want to create a separate caption with that lower case letter in the category (note that the first lower case letter caption starts only after the last upper case letter caption)

*Don't start the category sort key with a lower case letter, unless you want to create a separate caption with that lower case letter in the category (note that the first lower case letter caption starts only after the last upper case letter caption)

*When trying to sort with ''numbers'' (e.g. [[wikipedia:Naming conventions (pieces of music)]]), don't forget to add an extra zero when more than 9 entries in the category are expected; and a second extra zero when more than 99, etc...: <s><nowiki>[[Category:Symphonies by Joseph Haydn|Symphony 13]]</nowiki></s> → <nowiki>[[Category:Symphonies by Joseph Haydn|Symphony 013]]</nowiki> (he wrote 108 symphonies). Categories sort by the first character, so leaving out the preceding zero would cause 10 to be sorted before 2.

*When trying to sort with ''numbers'' (e.g. [[Centiare:Naming conventions (pieces of music)]]), don't forget to add an extra zero when more than 9 entries in the category are expected; and a second extra zero when more than 99, etc...: <s><nowiki>[[Category:Symphonies by Joseph Haydn|Symphony 13]]</nowiki></s> → <nowiki>[[Category:Symphonies by Joseph Haydn|Symphony 013]]</nowiki> (he wrote 108 symphonies). Categories sort by the first character, so leaving out the preceding zero would cause 10 to be sorted before 2.

*Ordinals often have to be converted to Arabic numerals: e.g. ''Pope John IX'': <nowiki>[[Category:Popes|John 09]]</nowiki> (+ zero added, there are XXIII popes with the name John)

*Ordinals often have to be converted to Arabic numerals: e.g. ''Pope John IX'': <nowiki>[[Category:Popes|John 09]]</nowiki> (+ zero added, there are XXIII popes with the name John)

*Don't forget to convert letters with diacritics, or non-standard letters to the nearest standard letters (that is: "standard" in English, at the time Wikipedia is written), examples:

*Don't forget to convert letters with diacritics, or non-standard letters to the nearest standard letters (that is: "standard" in English, at the time Wikipedia is written), examples:

===Year categories===

===Year categories===

:''See also [[wikipedia:naming conventions (numbers and dates)#Articles on other standard time periods]]''

:''See also [[Centiare:naming conventions (numbers and dates)#Articles on other standard time periods]]''

In categories which are years, such as [[:Category:2004]], special sorting guidelines apply:

In categories which are years, such as [[:Category:2004]], special sorting guidelines apply:

* Entries should generally be sorted by ''topic'', so the article [[2004 in film]], for example, would contain the category reference <tt><nowiki>[[Category:2004|Film]]</nowiki></tt> while [[2004 Canadian budget]] would contain the reference <tt><nowiki>[[Category:2004|Canadian budget]]</nowiki></tt>; [[List of religious leaders in 2004]] would contain <tt><nowiki>[[Category:2004|Religious leaders]]</nowiki></tt>.

* Entries should generally be sorted by ''topic'', so the article [[2004 in film]], for example, would contain the category reference <tt><nowiki>[[Category:2004|Film]]</nowiki></tt> while [[2004 Canadian budget]] would contain the reference <tt><nowiki>[[Category:2004|Canadian budget]]</nowiki></tt>; [[List of religious leaders in 2004]] would contain <tt><nowiki>[[Category:2004|Religious leaders]]</nowiki></tt>.

* The article about the year itself, [[2004]], should be sorted first among all articles by using <tt><nowiki>[[Category:2004|*]]</nowiki></tt>.

* The article about the year itself, [[2004]], should be sorted first among all articles by using <tt><nowiki>[[Category:2004|*]]</nowiki></tt>.

* Articles for individual months, such as [[October 2004]], should be sorted ''chronologically'' in the first section on the category page, in this case using <tt><nowiki>[[Category:2004|*2004-10]]</nowiki></tt>.

* Articles for individual months, such as [[October 2004]], should be sorted ''chronologically'' in the first section on the category page, in this case using <tt><nowiki>[[Category:2004|*2004-10]]</nowiki></tt>.