Categories Discussion

Discussion of Wiki Categories


You might put some text on pages like CategoryHome Page to explain the idiom you're using for indexing. -- Jim Coplien (May 1997)

The important thing is - if you create a category, index it in Category Category, otherwise it isn't properly indexed. -- John Fletcher (May 1997)

I'm not sure if this is the right place to ask: I'm thinking about doing PalmOS development, and I'm finding a bunch of good stuff on this wiki. But perhaps I would find more stuff if there were some sort of PalmOS category tag, similar to the CategoryPlatform series of tags. Should I make up a new category tag and stick it to the end of all the relevant pages I see? Or just make sure the word "Palm Os" is mentioned in all those pages, so it can be used as a category? Should I mention "PalmOS" in CategoryCategory? It's OK if I add this single word to lots of pages if I hit the "minor edit" checkbox, right?

-- David Cary (2003-08-26)

This has happened [CategoryPalm Os Category Handheld Personal Digital Assistant] 8-15-2009

I removed CategoryCategory from CategoryPalm Os today and replaced it with CategoryPlatform. Quite likely more categories will apply there. CategoryCategory is to be considered the root of the The Category Tree. In no case it would be useful to have CategoryCategory and one or more category tags together on any page. Names of categories i.e. Wiki Names like CategoryXsomething should always come in the last lines of a page and mentioning of such names within the text should be inactivated by using the 6's. --Manorainjan Holzapfel 08112014

I disagree with this action. I understand the point that Category Category is at the root of the tree, but it also serves as an index. I think it is useful for the subcategories to be listed in it so that someone can find all the categories in one place. The structure does not have to be a pure tree. -- John Fletcher

If there is no category in another category and not in the root category, than the tree is no tree and there is no hierarchy at all. And for what good reason would one need to use the root category as index for all other categories? Is is not enough to find absolutely all categories in an alphabetically listed result when you use the title search for "Category"? That works independently from the question of categorisation of category pages. By category-list You get 496 categories now. By search for category You get 548. Here is the Index of all categories: There is no need to build one or to do anything at all for its existence or maintenance. It works better than the list by clicking on the title CategoryCategory under all circumstances, because those reverse indexes via page title are depending on the daily indexing and the title search function includes new pages instantly. What more could anybody want? --Manorainjan Holzapfel

I disagree. What is proposed above is a search for all titles including the word Category, which is wider than just the ones in Category Category. My argument is based on what is useful for the reader, which I judge is to be able to see a quick list of all the categories which exist, in order to choose what is needed. -- John Fletcher

Suggestion: Add a CategorySandbox or something similar.

I'm new to Wiki, and made some large mistakes this week, mostly by accidentally/unknowingly polluting Recent Changes with what I regarded as experimental/demo pages that are considered off-topic for a wiki focused on programming. I have since learned that I can reduce such pollution by checking "minor edits", but wonder if a new category which one might call CategorySandbox or something similar (CategoryDemo, CategoryTemporary, CategoryExperimental, CategoryNewbie) might be useful in isolating newbie behavior. Indeed, if these categories were automatically included at the bottom of new pages formed from Wiki Wiki Sandbox, to the category home pages of newbies, and to the pages built from newbie category home pages, you would have a very convenient way of knowing that the errors of judgment were just that, and that a bit of corrective honey might be more usefully applied than the venom that I recently experienced. My errors are still my fault, and its still my job to correct them, but it honestly wasn't obvious to me, when I first arrived, that off-topic experimental behavior would not be treated gently here, or that it even be seen as off-topic. -- Davis Foulger (October, 1991) [1991?!]


It took me a while to understand what is going on. Then I realized the power of this. I have created Category Book for pages describing a single book. I wouldn't have done that separately from Category Books if it had been indexed in Category Category (it is now). I think the two are distinct, just, in that pages in the second category contains lists of books.

Since I made the comments above at the end of February 1997 the number of items in Category Book has steadily grown. This is not just me. Categories work best when someone who creates a pages also puts it in a category. -- John Fletcher (May 1997)

I think the original Patterns topics are well covered by Category but that much of the languages discussion is not, as some authors didn't see it as useful.

Some discussion moved to Citation Problem.


This sounds a lot like Meta tags and XML. Why does it seem like much of Wiki is reinventing the Wiki Wheel? Would it be possible to have some sort of external script map out the whole Wiki World, and a weblog analysis to show which pages are viewed the most? The lack of dates is also disorienting. Everything is timeless and immortal. See Wiki Now, and other pages on the philosophy of Wiki.

Word! For weblog analysis, see Wiki Statistics. -- Lars Aronsson (18 May 2001)


Categories were first introduced along with topics. One was for page form, the other for page content. It was learned that page form is not important enough to have a Reverse Index.

What's the difference between the two?

Doesn't seem like Topics ever caught on, but I've been using Categories a lot recently and I think that I really like the results. -- Phil Goodwin

April 2000. I am visiting after about 4 years absence. I am interested to see that Category Book has taken off quite well. I couldn't understand the difference between a Topic and a Category at the time. I use Category in my own work using the Swiki system. -- John Fletcher

Other Wikis

For another implementation of the Category idea take a look at Striki Wiki. This uses a Category System for most of its Wiki Navigation. Every Page has a Category (called Form). It is also possible to go sequentially through every page of a category. -- Jeroen Mostert

Which categories are useful?

I have been using Category Empty to make a new page where I would like some information. This makes the page prominent in the Recent Changes and often someone puts something into it. A bit like Fishing In Reverse.

Ease of Use

I have also been adding Category and Topic to pages. I think what I am doing could be described as Refactoring By Reverse Index through using the Category and Topic definitions as I understand them. The purpose of this is to add some richness to what is already there, by making it easier to find it, regardless of the names the pages actually have, and the reason the page originally was put there.

This is an excellent idea. The purpose of wiki categories is to simplify the search for pages having a common theme. It is important to have a reasonable number of members, probably between 5 and 500. Do not create categories that do not have at least the minimum number of members. It a category approaches the upper limit it it probably time to subdivide. On some other wikis this feature is called Topic Maps. See: and .

Automatically Generated Index

There is some evidence on e.g. Category Cpp of hand prepared indexes when the time could have been spent putting CategoryCpp in pages. CategoryJava is the same. CategorySmalltalk didn't exist until I made it yesterday. These are areas where there is a lot of good material on pages which do not have the language name in the title. I know that it takes a few days for the index to be updated. That doesn't matter as it is all a long term thing anyway. Like Science Citation Index.

The list is made available via the backlinks feature. Double Clicking the Category Page Title will list all pages categorized by the Page's Name. Therefore no manually created list is required. It may however be helpful to list associated or related categories on the page.

Here are some of the issues for determining the best way of evaluating the usefulness of categories:

The categories can be added later, by someone other than the original author of the page, who may not have chosen to categorize.

The categories and topics may well not be obvious from the page names. See for example CategoryCpp.

I think for various reasons some areas are better covered than others.

For me the main reason for doing item (1) is for the benefit of future searchers in the increasing archive. One way of looking at this is that Wiki Wiki is like a sediment depositing steadily at the bottom of a lake. Someone else coming along later is like a fossil hunter, after nuggets of information relevant to them.

There may be areas of discussion where the absence of a category doesn't make a problem. The main areas for me where they are useful are where wisdom has been shared about how to tackle a problem.

A category should be specific and focused. To create a category for Programming Languages would be far to wide of a category to be useful.

Categories and topics serve best as a sort of table of contents. As such it serves as a guide for the casual reader to pages most likely of interest.

Why go to the trouble of Categorizing?

When I first came across this, I wondered why people should go to the trouble of adding categories to their pages. Surely, doing a search will be more comprehensive and more up-to-date. Then, I realized that this approach assists in solving the problem of synonyms, etc. If you go to Category Year Twok and press the title, you will see that it finds pages which have Category Year Twok in them, but these pages might well only have Y2K, or Year 2000 or Millennium Bug. By adding a single category, it saves future users the need for conducting multiple searches (if the category methodology is applied to all pages, of course!)

Similarly, I found that there were all sort of pages floating around which provide insights into how Wiki works and how best to use it, so I have been progressively indexing or is it categorizing any relevant pages I find. Newcomers can then simply click on Category Wiki, press the title and find all pages which might offer them help in becoming familiar with Wiki. -- Peter Murchland (August 1998)

Clustering Instead of Categories

I think the whole idea of categorizing is flawed. A category functions like a container and the problem is that nothing really fits well in a container since all things that are distinct are distinct because they have distinguishing properties. The notion of clustering seems more helpful to me. A cluster is defined by some sort of similarities or family resemblances and is more friendly than a category. The whole pattern movement is more about producing generative patterns that are interrelated in pattern languages and that's more like a cluster or a network with distance links so that clusters are things that are near one another so that a boundary with a specific radius would surround the members of the cluster. -- Ray Schneider

Are you taking into account the fact that a given page can belong to any number of categories simultaneously? So, rather than being a container, a category acts more like an identifier for similar pages, which sounds like what you're getting at with the concept of clusters.

That's true enough isn't it? A Category is a set of pointers to the members of the Category and a given page can be pointed to by an arbitrary number of categories. I'm not sure that changes my point because I think the issue is more the connections among the pages than the connections imposed by the categories. That might really be a experimental issue. What is really being done with the categories? In fact if things are too much alike in a category, it seems like the pages that make up the category should be conflated/combined because the pages are redundant. But the connections among the pages, how one traverses from pattern element to pattern element or page to page may be more informative. I also put a brief comment on link analysis on Discussion On Really Valuable Pages. -- Ray Schneider

There's always going to be pages that we need to Refactor By Merging, but would any categories disappear as a result? Take CategoryTesting for example. As of this writing (2003-07-11) it contains 142 pages on a variety of topics related to testing: testing philosophy, Testing Frameworks, practical advice, etc. Merging pages makes sense for some pages in the topic but certainly not all.

Categories (and "See ...") work. Are you proposing another mechanism to create connections between related pages, or suggesting that we link more aggressively?

Someone once wrote on Category Education: "Categorization is something people engage in too much today. People aren't comfortable with that which they can't categorize."

Categories: form vs type

[originally at Category External Link, circa 2001]

I have just finished deleting topics. Originally topics were for page content (e.g. Java or use cases) and categories were for page form or type (e.g. discussion or faq). It turns out both categories and topics were used overwhelmingly for page content, and those few categories that were tried for page form or type didn't catch on.

My conclusion is that categories that explain the form or type of a page are not useful. Categories that explain the content of a page are useful.

However, CategoryHomePage is very well liked and seems useful. I don't understand this, because home page is like a form or type tag. But maybe it is a content tag in disguise. If someone could explain why this is liked and useful, and whether it is really a form or type tag, I would appreciate this.

So I vote to delete this page, and all other form or type categories (except those such as CategoryHomePage that are found useful). As with other things on wiki, though, if there is much squawking, I wouldn't bother.

Form or type categories I don't find useful:

Category''''''Glossary Category''''''Idea Category''''''Discussion Category''''''Definition Category''''''Index

It is good to keep in mind that completeness, correctness, and consistency are sometimes the friends of usefullnes, and sometimes the enemies of usefulness. With categories, I think they are enemies.

to a common category (perhaps CategoryGlossary or CategoryDictionary). This Wiki Is Nota Dictionary but a number of such pages have been created with such content. The category might be useful for some users searching for basic information, it might be useful at some point to delete these pages or split these pages off into a separate dictionary wiki.

I think Marko Schulz was disappointed that no real discussion [about Category External Link] ("prove me that this category is useful or necessary") developed. The refactoring above shows his frustration. But such a discussion would have been pointless. I think that a wiki must provide enough space for divergent opinions to live side by side. It would be desastrous if some rule ("no form or type categories") could be used as to bar the invention of new categories. On the other hand the creator is responsible for filling the category and making it popular. If after some time the category is unused, it should be deleted.

I don't think that we really understand the wiki and I don't think that we understand categories. Different categories may serve different purposes. Some may exist for searching information, some may be part of a social ritual, some may prepare for a split or OT-content-removal, some may just partition the semantic space, some may serve multiple purposes. This complexity is beautiful, it has to do with Quality Withouta Name.

I think that the system of categories can't be further optimized at the moment. Categories have to develop with the content. But the content of this wiki is in an unstable state until Ward redefines The Mission Of This Wiki.

From the co-founder of Wiki Pedia:

Two final comments, directed to the Wikipedia community. First, you should completely scrap the "category" system for Wikipedia articles; the articles serve as their own nodes in a category system; I thought everyone realized that; there's no need to superimpose a redundant category system on top of the one that already exists....

My feelings about categorization are similar. I think we should only keep a few useful categories like CategoryHomePage and perhaps not even those. Take a look at the pages belonging to Category Regular Expressions. The term 'Regular Expressions' should be already somewhere on those pages. If it isn't, the page should be refactored to Make It So. In cases like this, the category system is redundant. With categories like CategoryAutoIgnore and CategoryHomePage, there is not really a 'natural' alternative, other then "This is my Home Page" and "This page should be Auto Ignoreed", so categories may be the best solution here. But in general, it works pretty good, but is largely redundant in my eyes. -- Aalbert Torsius

From my Home Page, slightly shortened (Delete When Cooked):

Gunnar Zarncke, why are you introducing ProgrammerStereotype rather than CategoryProgrammerStereotype?

a) I'm not sure if it is a category. b) Fallacious Argument doesn't start with Category either. In short it just seemed appropriate, but I may have been wrong.

I hope Gunnar won't mind me jumping in here, but I think this is a case (indeed, like Fallacious Argument) of a category being a worthwhile page by itself. Categories don't need the 'Category' postfix to work. In fact, I feel a lot of them would be better of without it, and if we could solve the Wiki Single Word Problem, we wouldn't need it at all. -- Aalbert Torsius

I just tentatively added CategoryCategory and wouldn't mind if anybody removed it. -- .gz

As for ScreaminglyObvious, I can't really say any more. says very little now indeed. Sorry. -- .gz

The inclusion of the prefix "Category" facilitates maintaining the pages relating to the categorization project currently being undertaken by various wikizens.


I recently added LazyPattern with the CategoryCategory tag

Now changed to CategoryLazyPattern

I checked: Fallacious Argument doesn't have it (though it really feels like one). What to do? Make all three real categories (it will be quite tiresome for Fallacious Argument) or remove the tag from both (for regularity)? -- .gz

I don't mind adding CategoryFallaciousArgument to a few score pages if that is acceptable to others. I haven't looked into the other two cases yet.

Here are some additional pages you might want to read about categories and Categorization:

See original on