User:DexDor/Namespaces and categories

This is an essay on Wikipedia categorization.

It contains the advice or opinions of one or more Wikipedia contributors. This page is not an encyclopedia article, nor is it one of Wikipedia's policies or guidelines, as it has not been thoroughly vetted by the community. Some essays represent widespread norms; others only represent minority viewpoints.

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User:DexDor/NSCat

Every Wikipedia page (e.g. an article, a talk page or even a redirect) is in a single namespace. Many/most Wikipedia pages are also in one or more categories. This essay contains the results of an analysis of how these 2 schemes interact - i.e. how pages in each namespace fit into the category structure. In particular, it identifies combinations of namespace and category that are not valid for any pages - for example, there should be no user talk pages below Category:Articles and there should be no articles below Category:Wikipedians.

This analysis only considers the combination of namespace and some of the highest level Wikipedia categories - e.g. Category:Wikipedia books and Category:Disambiguation pages. A diagram showing the relevant part of the category structure can be found below the table.

Namespace-category matrix

Note: The information in this matrix should not be used directly to support an argument about whether or not a particular page should be in a parent category. However, this matrix may indicate where the applicable policy/guideline can be found.

The analysis was carried out in 2014-2016 using category intersection tools. Some aspects of the analysis are currently incomplete and may not incorporate later changes to the categorization structure.

Explanation of matrix

The matrix is designed so that each page in the English Wikipedia satisfies the criteria for one (and only one) of the rows.^[1] Which row a page matches is determined primarily by which namespace the page is in; for some namespaces other criteria are also considered -

Some rows are only applicable to disambiguation pages (i.e. pages that are under Category:Disambiguation pages) or non-disambiguation pages. The column headed "D?" indicates whether each row includes disambiguation pages - "Y" means only dab pages, "N" means excluding dab pages and "-" means either.

Some rows are only applicable to hard redirects or to pages that are not hard redirects. The column headed "R?" indicates whether each row includes hard redirects. "Y" means only hard redirects, "N" means excluding hard redirects and "-" means either.

Some rows are only applicable to subpages. The column headed "S?" indicates whether each row includes subpages. "Y" means only subpages, "N" means excluding subpages and "-" means either. Subpages are not allowed in some namespaces.

Some rows are only applicable to pages that are, or are not, in certain categories.

Having identified which row of the matrix a page belongs to the coloured cells on that row then indicate which high-level categories the page should/may be in (green cells) and should not be in (pink cells). The matrix can also be used in the opposite way; for a particular high-level category it is possible to go down the corresponding column to see what types of pages are expected to be in that category. Amber cells indicate where there is currently uncertainty about whether or not that is a valid combination. A more detailed key to the colours is provided below the matrix.

Note: Some pages belong in several columns and a small number of pages don't belong in any of the (current) columns.^[a]

Matrix

Note: watchlisting this page will not show changes to the matrix - for that it's necessary to watchlist a separate page.

Note: After the template has been changed it may be necessary to Purge this page.

Top-level category structure

The diagram below shows some (probably the most important) categories at the top levels of the category structure. The two-letter codes are those used in the matrix above.

Contents

Wikipedia administration

Other (see below)

Wikipedia templates
(CT)

Wikipedia redirecting

Wikipedia essays
(CE)

Wikipedia disambiguation

WikiProjects
(CW)

Wikipedians
(CU)

Wikipedia files
(CF)

Inactive project pages
(CI)

Wikipedia redirects
(CR)

Disambiguation pages
(CD)

Other categories directly below Category:Contents (as of July 2016) are Category:Wikipedia categories‎, Category:Featured content, Category:Glossaries, Category:Image galleries, Category:Indexes of topics, Category:Lists‎, Category:Outlines, Category:Timelines‎.

Categories for pages that readers are expected to deliberately navigate to (via categories)

Categories for pages that only editors are expected to navigate to

Finding and fixing anomalies

Category intersection tools can be used to detect pages that are at an anomalous combination of namespace and high level categories; the appropriate changes to the categorization can then be made. Links to some category intersection queries and advice on fixing the mis-categorizations discovered can be found at User:DexDor/FHL.

The matrix above shows that there are some pairs of columns for which there are no types of pages, apart from category pages, that are valid in both of those columns. For example, there are no rows for which there is a green cell in both the CA and CE columns - i.e. there should be no pages in both Category:Articles and Category:Wikipedia essays. Thus, there should be no categories at that intersection. This can be checked using a category intersection query on the Category namespace. However, it's rare to find categories mis-categorized in this way so in general it's best just to look for (non-category) pages that are at an anomalous namespace/category combination as that will also uncover most incorrectly categorized categories (assuming that the category contains at least one page).

Maintenance of the matrix

The namespace-category matrix shown above is generated using a template (User:DexDor/Cmtp). The advantage of using a template rather than placing the details directly in this page is that parameters can be used to control how the template is displayed - thus, the template can generate both the compact format shown above and a longer more detailed format used during development/maintenance of the matrix. There is also a similar template which expands the CA column into lower level article categories.

To be done:

Remove all unnecessary detail (including references) from the compact format of the matrix.
Fix all "TBD"s (if possible).
Have the number of months before a cell is flagged as "OLD" depend on the importance (e.g. whether it affects CA and how often pages get put in it).
Ensure every "no" cell as a "N" note.
Ensure every "tbd" cell as a "T" note.
Ensure every "some"/"all" cell is linked to at least one example.
Refresh all "OLD" cells.
Seek suggestions for improvements from other editors.
Consider whether checking of some cells could be improved by AWB, bots or database reports.
Move from User namespace to Wikipedia namespace (but would then have to explain each edit, length might increase unless use short names for templates).
Make other language Wikipedias aware of this (sharing ideas).
Improve the documentation of the templates used in this.
Should any more rows be split?
Reduce the number of pages that don't match any row.
Complete the diagram showing the top of the category hierarchy (and simplify that where possible).

Comments (e.g. about the status of a particular namespace-category combination or about the formatting of this page) are welcome on the talk page.

Notes

^ E.g. many of the pages that are directly in Category:Wikipedia disambiguation.
^ This "article" row is for any page in namespace 0 that is in Category:Articles, is not a hard redirect and is not categorized as a disambiguation page. I.e. it includes some pages that fall outside some definitions of "article" such as lists, outlines, soft redirects and stubs.

References

^ Note: Currently there may be a small number of pages that don't fit any row of this matrix.
^ E.g. there are articles below Category:Wikipedia articles incorporating a Leigh Rayment's Peerage Pages template that is below Category:Wikipedia sources.
^ Pages that are soft redirects (e.g. see Category:Redirects to Wiktionary) are at this intersection. Also (temporarily) hard redirects that are at RFD. Pages that have been (incorrectly) placed under a redirected category are at this intersection - see Category:Wikipedia non-empty soft redirected categories.
^ As of March 2015 there's also lots of pages at this intersection because of redirects in Category:WikiProject Artemis Fowl and Category:Redirects from books (which is, possibly incorrectly, categorized under a wikiproject).
^ Pages get here for a variety of reasons - (1) because a template (example) is created in Draft namespace and has been placed in a templates category, (2) a page in Draft namespace (example) uses a template in such a way that it puts the page in a tracking category (e.g. Category:WikiProject banners with formatting errors or Category:Geobox usage tracking for region type) that is under Category:Templates (which itself is dubious), (3) a page in Draft namespace (example) is in Category:Template test cases that is under Category:Templates.
^ As of November 2015: 108RinCR indicates that there are 255 hard redirects that are in Book namespace in Category:Wikipedia redirects. Wikipedia:Database reports/Page count by namespace shows there are 764 (presumably hard) redirects in Book namespace.
^ As of November 2015: 100RinCR indicates that there are 1587 hard redirects that are in Portal namespace in Category:Wikipedia redirects. Wikipedia:Database reports/Page count by namespace shows there are 11227 (presumably hard) redirects in Portal namespace.
^ E.g. "Please ... add [redirect] templates ... when you create a redirect".

[2] E.g. many of the pages that are directly in Category:Wikipedia disambiguation.

[3] This "article" row is for any page in namespace 0 that is in Category:Articles, is not a hard redirect and is not categorized as a disambiguation page. I.e. it includes some pages that fall outside some definitions of "article" such as lists, outlines, soft redirects and stubs.

[1] Note: Currently there may be a small number of pages that don't fit any row of this matrix.

[4] E.g. there are articles below Category:Wikipedia articles incorporating a Leigh Rayment's Peerage Pages template that is below Category:Wikipedia sources.

[5] Pages that are soft redirects (e.g. see Category:Redirects to Wiktionary) are at this intersection. Also (temporarily) hard redirects that are at RFD. Pages that have been (incorrectly) placed under a redirected category are at this intersection - see Category:Wikipedia non-empty soft redirected categories.

[6] As of March 2015 there's also lots of pages at this intersection because of redirects in Category:WikiProject Artemis Fowl and Category:Redirects from books (which is, possibly incorrectly, categorized under a wikiproject).

[7] Pages get here for a variety of reasons - (1) because a template (example) is created in Draft namespace and has been placed in a templates category, (2) a page in Draft namespace (example) uses a template in such a way that it puts the page in a tracking category (e.g. Category:WikiProject banners with formatting errors or Category:Geobox usage tracking for region type) that is under Category:Templates (which itself is dubious), (3) a page in Draft namespace (example) is in Category:Template test cases that is under Category:Templates.

[8] As of November 2015: 108RinCR indicates that there are 255 hard redirects that are in Book namespace in Category:Wikipedia redirects. Wikipedia:Database reports/Page count by namespace shows there are 764 (presumably hard) redirects in Book namespace.

[9] As of November 2015: 100RinCR indicates that there are 1587 hard redirects that are in Portal namespace in Category:Wikipedia redirects. Wikipedia:Database reports/Page count by namespace shows there are 11227 (presumably hard) redirects in Portal namespace.

[10] E.g. "Please ... add [redirect] templates ... when you create a redirect".

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Child page					Parent category
Name- space	Type	D?	R?	S?	None	Articles	Books	Dab pages	Essays	Files	Help	Inact.	Portals	Redirects	Temp- lates	Wikipedians	WikiProjects
0	Main Page	N	N	(N)	yes	no	none	no	none	no ?	no	no?	no^(NP)	no	no	none	no
	Article^[b]	N	N	(N)	never	all		never			tb d^[2]			s o m e			tbd^(TS)
	Other	N	N	(N)	no^(NC)	never					tbd			s o m e^[3]
	Dab page	Y	N	(N)	never	tbd^(NY)		all			n o ?			no			tbd^(TN)
	Redirect (hard)	-	Y	(N)	no?^(NA)	s o m e		none			none		so me?	all^(AR)			so me^[4]
2	User (excl. t.)	-	-	-	some	no^(NU)	n o^(NB)	no	some	tb d	s o m e?	tb d^(TI)	no?	some	never	some	some
	User (template)	-	-	-	never				none	no?	tbd	n o?		none	a l l	tbd	some
4	Wp dab page	Y	-	-	never	no	none	all	none	none	none	none	none	none	none	none	none
	Essay (not dab)	N	N	-	never			never	all	no	some?	so me	none	some?	none	no?	s ome
	Wp redir (hard)	-	Y	-	no^(NA)			none	s o m e ?	none	s o m e		so me	all^(AR)	s o me	none	s o m e?
	WikiProject	N	N	-	never			never	never	no?	t b d^(TH)		no ?	no	some^(ST)	s o m e?	all
	Wikipedia (other)	N	N	-	s o me^(SW)			never	never	tbd	s ome		t bd		some	tb c	never
6	File	-	-	(N)	no^(NA)	some?	none	none	none	all	s o me	s o me	some?	tbd	tbd	n o ?	t b d
8	MediaWiki	-	-	(N)	all	none	none	none	none	no	no?	none	none	s o m e	none	no?	none
10	Template	-	N	-	no	no?^(NX)	no ?	n o ...	none?	s ome?	t b d	so me	tbd	tbd	all	some^(SV)	some
	Template redir	-	Y	-						none	tbd	none	none	so me	t b d	none	tb d
12	Help	-	-	-	no?^(NA)	none	none	some	t b d	no	all	so me	none	some	s o m e ?	none	n o ?.
					None	CA	CB	CD	CE	CF	CH	CI	CP	CR	CT	CU	CW
14	Category:Contents	-	-	(N)	yes	no	no	no	no	no	no	no	no	no	no	no	no
	Category (other)	-	-	(N)	no	some	some	some	some	some	some	some	some	some	some	some	some
					None	CA	CB	CD	CE	CF	CH	CI	CP	CR	CT	CU	CW
100	Portal (dab)	Y	-	-	never	none	none	a ll	none	no	none	none	none	none	none	none	none
	Portal (h/redir)	N	Y	-	some^(SR)	none		never			none	no?	so me	s o m e^(SR)	none		t b d
	Portal (not d/sp)	N	N	N	no^(NA)	all?					no	t b d	all^(AP)	some	no		no
	Portal s/page	N	N	Y	some^(SP)	no					s o m e		some^(SP)	tbd	t b d
108	[[Wikipedia:Books\|]] (dab)	Y	-	-	never	no	none	all	none	none	no	none	none	none	none	none	no
	[[Wikipedia:Books\|]] (hard redir)	N	Y	-	some^(SB)	none	none	never			none			some^(SB)			none
	[[Wikipedia:Books\|]] (encyc'c)	N	N	-	no^(NA)	all?^(AB)	all				no			none			no ?
	[[Wikipedia:Books\|]] (Wp)	N	N	-	no?	no	a l l ?				some?
118	Draft	-	-	-	some	no^(ND)	n o^(ND)	no^(ND)	none	tbd	no?^(NS)	none	no^(ND)	some	no?^[5]	no	tbd
446	Ed. Program	-	-	(N)	some?	none	none	none	none	none	none	none	none	none	none	none	none
710	TimedText	-	-	-	some?	none	none	none	none	none	none	none	none	some	none	none	none
828	Module	-	-	-	some?	no ?	none	none	none	no?	tbd	none	none	some	tbd^(TM)	none	t b d^(TW)
					None	CA	CB	CD	CE	CF	CH	CI	CP	CR	CT	CU	CW
1	Talk	-	-	-	some	no^(NT)	no	none	none	tbd	t b d	no?	so me?	s o m e	tb d	no	some
3	User talk	-	-	-	some	no^(NT)	no	no		t b d	tbd	no?	none	s o m e	no?	s ome	some
5	Wikipedia talk	-	-	-	some^(SG)	no^(NT)	none	none		t bd	so me?	n o ?	none	s o m e	t b d	no ?	some
7	File talk	-	-	-	some	t b d^(T7)^(NT)	none	none		no	no	no	s o m e?	so me	none	none	some
9	MediaWiki talk	-	-	-	some^(SG)	no^(NT)	none	none		none	some?	no	none	so m e	none	none	some
11	Template talk	-	-	-	some^(SG)	no^(NT)	none	no?		none	t b d	t b d^(TI)	no?	so me	t b d	no	some
13	Help talk	-	-	-	some^(SG)	no^(NT)	none	none		none	some?	no?	none	so me	none	none	some
15	Category talk	-	-	-	some^(SG)	no^(NT)	none	no		none	some?	no?	none	some	none	no	some
101	Portal talk	-	-	-	some^(SG)	no^(NT)	none	none		none	none	n o?	no?	some	none	none	some
109	[[Help:Using talk pages\|]]	-	-	-	some^(SG)	no^(NT)	no	none		none	some?	no	no	so me	none	none	some
119	Draft talk	-	-	-	some^(SG)	no^(NT)	none	none		no?	none	no	none	so me	none	none	some
447	Ed. Prog. talk	-	-	-	some^(SG)	no^(NT)	none	none		none	t bd^(TE)	no	none	none	none	none	some
711	TimedText talk	-	-	-	some^(SG)	no^(NT)	none	none		none	none	no	none	some	none	none	some
829	Module talk	-	-	-	some^(SG)	no^(NT)	none	none		none	none	no	none	so me	t b d .	no?	some
2600	Topic	-	-	-	all	none	none	none	none	no	none	none	none	none	none	none	none
					None	CA	CB	CD	CE	CF	CH	CI	CP	CR	CT	CU	CW
Note: The following namespaces are not shown in the table above: 2300&2301 (Gadget) and 2302&2303 (Gadget definition). Legend: Column headings Row definitions Not a possible combination (i.e. there can not be any pages at this position) A Wikipedia guideline says (or the existence of a database report implies) that there should be no pages at this intersection Few/no pages are found at this intersection - and any such pages are probably mis-categorized Should be empty, but pages often get placed here (often temporarily) and it doesn't matter that much Is/possibly a valid namespace-category combination Valid - by definition every page in that row must be in that parent category (but not necessarily vice versa) To be decided - e.g. further investigation or discussion needed to resolve whether or not this is a valid combination Notes about why a particular namespace-category combination isn't valid: (NA) - As there is an "all" elsewhere on this row then there should be no uncategorized pages of this type. (NB) - See note ("Do not categorize books from the User: namespace (user books) ...") at Category:Wikipedia books and Wikipedia:Categories_for_discussion/Log/2010_April_27#Wikipedia_books. (NC) - See, for example, Category:All uncategorized pages. (ND) - WP:DRAFTNOCAT says "Pages in the draft namespace ... do not belong in content categories..." - however, in practice many draft pages are placed in article categories temporarily and this does little harm (user pages in article categories is much worse). (NI) - Wikipedia content (articles etc) should not overlap with Wikipedia administration (wikiprojects, user pages, talk pages etc). I.e. a content category should not be under an administration category and vice versa. (NP) - "This category is meant to contain pages ... in Wikipedia's portal namespace. It should not be used to categorize articles or pages in other namespaces." (Category:Portals, August 2014). Note: when a redirect (e.g. to portal space) is taken to RFD it is not considered by Catscan to be a redirect and hence (for the period of the RFD) will be listed. (NQ) - WP:CAT#T: "... Category:String quartets by composer templates ... should be a subcategory of Category:Music navigational boxes (kind) but not Category:String quartets (content)." (NS) - In the spirit of WP:DRAFTNOCAT. (NT) - "... discussion pages ... are not articles." - Wikipedia:What is an article?, August 2014. (NU) - "User pages are not articles, and thus do not belong in content categories such as Living people or Biologists." - WP:USERNOCAT (as of August 2014) (NX) - "... templates ... are not articles." - Wikipedia:What is an article?, August 2014. (NY) - "Disambiguation pages ... are not articles." - Wikipedia:What is an article?, August 2014. Notes clarifying the definition of a row: Some rows (e.g. the "Articles" row) have a mouseover. Notes about why there's a "some" in the table: (SB) - About a third of hard redirects in Book namespace are uncategorized^[6] and there is no obvious way to identify such redirects. (SG) - A talk page can be navigated to from the associated non-talk page so categorization of the talk page itself is unnecessary. (SP) - Currently (March 2015) some portal subpages are categorized under Category:Portals and some have been left uncategorized. Rather than have a debate about how these subpages should be categorized both options are currently shown in the table as "some". Wikipedia:Portal/Categorizing#Topical_portal_categories says "A portal that transcludes content in from separate subpages can be given its own category to help portal editors manage the components that come together to form the portal. Such a category is not mandatory, but recommended.". (SR) - Most hard redirects in Portal namespace are uncategorized^[7] and there is no obvious way to identify such redirects. (ST) - There are many templates in many namespaces and (afaik) there is no rule against this. Help:Template says "some template pages are placed in other namespaces". (SV) - Lots of templates that are intended to place a page in a category (e.g. a userpage in a Wikipedians category) also (inadvertently) place the template itself in that category. This is often because includeonly markup is negated by it being on a template documentation page. (SW) - Attempting to ensure that every page in Wikipedia namespace is categorized is unlikely to be worth the effort it would take. Afaik there's no database report to find uncategorized pages in the Wikipedia namespace. Notes about why there's a "TBD" in the table: (T7) - Lots leak via Category:Spoken article reviews. (TA) - As of Aug 2014 there are township dab page cats and cyclone dab page cats. (TE) - See discussion at DexDor's talk (March 2016) re " supported by Wiki Ed". (TH) - This is a "TBD" pending discussion of scope of Help namespace and scope of WikiProjects. (TI) - Category:Inactive project pages makes clear that it's for project namespace pages (i.e. pages in the Wikipedia namespace). However, Template:Historical has been added to some pages in other namespaces - including to category pages. (TM) - As of December 2015, many modules (i.e. pages in Module namespace) are categorized in a templates category - however, there is also Category:Wikipedia modules. (TN) - As of January 2016, Category:Pages using New York City Subway service templates is putting lots of pages, including dab pages, under a wikiproject category. (TQ) - Many book categories are placed in article categories (e.g. Category:Wikipedia books on Berlin is in Category:Berlin), although not always in a consistent way. Note: Books (like portals) are considered part of the encyclopedia content (not administration). (TS) - For example, Category:Aviation stubs is in Category:Stub categories which is below Category:WikiProject Stub sorting (as of March 2015). (TW) - As of December 2015, some Module namespace pages are in templates categories (which might be OK), but then the template category is in a WikiProject category (e.g. Category:Map templates is (via other categories) under Category:WikiProject Geography - which is probably wrong). Other notes: (AB) - "When adding a book category to its corresponding encyclopedia category ..." (Category:Wikipedia books, August 2014). However, as of 16/5/2015, many Wikipedia books about encyclopedic topics are not in an article category (e x a mples). (AP) - Check this as some (e.g. Category:Ancient Near East portal) aren't. (AR) - Some editors prefer redirects to be categorized.^[8] However, the main reasons why categorization is useful for articles (navigation, spotting content forks etc) do not apply to redirects and there is, AFAIK, no database report of uncategorized redirects.