I've made some noise in this direction in the past, but I'm working on a proper proposal to this effect that I think will really help fix some of our deletionism/mergism issues in a way that both preserves the unique content we have and keeps articles clean and informative.
I have a version of this proposal at [[User:Phil Sandifer/Extensions]] that I invite people to hammer at. Once I have it in more detail I intend to take it to the Village Pump.
==Purpose==
Wikipedia, as we often note, is not paper. But Wikipedia is fundamentally organized like paper - individual articles are still linear stretches of text that are organized, essentially, for printability. And that's good - the idea of an encyclopedia article is, structurally, linear. But it does lead to problems with a lot of information that is accurate, informative, and seems to be viewed as valuable by our readers. This information often does not fit in well with the linear structure of articles, and the system of sub-articles leads to mixed results (as evidenced by waves of deletionism, mergism, etc)
The Extensions namespace is intended to house information on articles that is relevant, accurate, and interesting, but that does not fit into a traditional encyclopedic overview of the subject.
==Precedents==
Citizendium has a version of this, which you can see on any of their articles. They call it subpages, and have a separate tab for each subpage. This is very sleek and nice, but probably unsuitable for our purposes. User-editable interface aspects would probably spiral out of control in a categories-esque fashion.
The idea of pages that organize subtopics, of course, is similar to the Portal namespace, but that seems unsuitable to this task for two reasons - first, it's really designed for top-level topics, whereas an Extensions page makes sense for smaller topics. Second, it's not well- integrated into the site interface, and so it's not really a concept accessible to the casual user.
==Scope==
My intention is that this would be used for information that is beyond the scope of articles of any sort. That includes a large amount of stuff that is often slammed as "cruft" but also things that are routinely included without question. Among the things that would be suitable:
*Plot summaries *Lengthy tables *Bibliographies, filmographies, and other such lists *Trivia and "In Popular Culture" sections *Derivations and figures (i.e. the "axioms" section of [[Zermelo– Fraenkel set theory]]) *Lists of characters, actors, etc.
The Extensions namespace could also include full-fledged sub-articles - things like [[Early life of George W. Bush]] - but they do not have to, and it may not be preferable for them to. See also "Unsolved issues" below.
==Implementation==
Imagine an article such as [[The weather in London]], which is assumed to have an accompanying talk page. The Extensions namespace would also implement [[Extensions:The weather in London]], and this would be linked to with a tab next to the Discussion tab - perhaps called "More information," or simply "Extensions."
Clicking the tab would lead you to the relevant Extensions page, which would be an organized list of links to individual extensions - perhaps tables of individual months and years of weather, the weather in London in popular culture, etc. All of these would be subpages of the extensions page - so, for instance, [[Extensions:The weather in London/ In popular culture]].
Breaking up the individual Extensions like this does increase our vandalism targets significantly, but it means that the main Extensions page can be carefully and neatly organized and scannable, and that individual figures, tables, and sections can, where relevant, be directly linked from within articles.
==Unsolved issues==
Some of these would need to be smoothed out before the namespace was launched:
*What should the namespace be called? *What should the tab in the site interface read? *Should watchlisting an article automatically watchlist the extensions (as is the case with talk pages)? *Are there more issues we need to solve?
Others are things we'll want to think about, but that decisions about will probably need to be field-tested, and that should therefore should be left to the community to decide and create norms on.:
*Where should the line between sub-article and extension be drawn? Obviously, for instance, [[I Robot]] should not become an extension of [[Isaac Asimov]]. But should [[Early life of George W. Bush]] be an extension of [[George W. Bush]]? Doing so would probably wreck a number of featured articles. But on the other hand, does it really make sense to have those be separate articles? *What are our content policies for extensions? Obviously notability gets blurrier here. Plenty of people have expressed concerns about, for instance, plot summaries and trivia sections in terms of verifiability. Others have disagreed that either pose a serious complication or problem to these policies. Ideally extensions would provide a middle ground for such things - allowing a place where we can be more permissive without hurting our overall quality. But how much more permissive? *How should the main extensions pages be organized? *How should individual extensions be linked to within articles? (In the form of "Main article: Topic" or through small sidebar boxes, for instance.) *What extensions should be linked to from within articles, and what extensions should be linked only from the extensions page?
-Phil