Template:Category intersection

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Please note that there is a slight delay from when an article has been categorized (or uncategorized) until you can see the effect with the "incategory"-function.

Explanation

 * Link text displayed = What the link will look like when displayed. For example "Novels awarded both the Hugo Award and the Nebula Award for Best Novel".
 * Category 1 = Name on the first category. For example "Hugo Award for Best Novel-winning works".
 * Category 2 = Name on the second category. For example "Nebula Award for Best Novel-winning works".
 * A maximum of five categories can be stated.
 * The sixth category is an excluding category

Example

 * generates a list of articles that are categorized into both "Category:Hugo Award for Best Novel-winning works" and "Category:Nebula Award for Best Novel-winning works" (not either) and thus a list of novels that won both the Hugo and the Nebula award. Syntax:
 * (and with syntax  )
 * (but since the category New York University alumni is not fully populated, the example excludes and others. A fully populated New York University alumni would return a list of all alumnis)

Rationale

 * To reduce the need to update lists like List of joint winners of the Hugo and Nebula awards
 * To ease, and illustrate the need for, the move towards fully populated primary categories. The general rule should be: If a category can be completely and totally expressed as the intersection of other categories, it is not a primary category and its content should be generated dynamically instead. For example, the content in Category:American film directors can be defined as the intersection of Category:Film directors and Category:American people. Another example: Had the categories Category:Ornithological organizations and Category:1994 establishments been fully populated, a search of the intersection of the two would have returned a list longer than the current and not leave out for example Southern Oceans Seabird Study Association which meet both criteria but is categorized in Category:Ornithological organisations in Australia, a subcategory to Category:Ornithological organizations.
 * To illustrate the need for a powerful, intuitive, easily accessible, easy to use category intersection tool integrated in Mediawiki to facilitate and encourage users retrieving and discovering information by basic data mining. Hopefully this will also lead to increased public awareness of, and knowledge about, data mining. And let's be honest: It would be crazy fun too!