User:Demi/Notability
Definition
To me, notability means something which is known outside of a narrow interest group or constituency. It's an extension of the notion of "notoriety" for biographical articles for biographical articles.
Justification
I've heard it argued that "notability" is not a criteria for deletion, because (among other things) this isn't specifically stated in the Deletion policy; and since Wikipedia is not paper with (in theory) no size limits, there's no reason we shouldn't include "everything" that fits in with our other criteria, such as verifiability and Wikipedia:no original research. In other words, a subject's perceived "importance" or "fame" is no criterion for deletion or inclusion.
I propose that notability, while directly pertaining to importance and fame, is also a useful surrogate for the notions of verifiability and original research, since those, in turn, go hand-in-hand with notability--at least, by my definition.
Since Wikipedia is not a primary or secondary source, much less a vehicle for publication of direct observation, non-notable subjects do not belong in it. Inclusionists have said, "Why not write an article on your next door neighbor's dog, as long as it's verifiable and NPOV?" Well, for one, because it's original research--your direct observations of your dog. If the dog appears in a reputable publication, that's another story.
Notability also speaks to verifiability. There is a level of ease with which facts can be checked that must be maintained in order to be verifiable: theoretical verifiability isn't enough. Your garage band in Seattle may consist of Mike, Jeff, Scott and Mike, and that may theoretically be verifiable (if I traveled to Seattle); but that's not enough. I need to be able to look it up in a book, or on the web or something. And not just any source: blogs, zines, e-zines, stuff you printed up, CDs you recorded yourself, etc. don't count as "sources."
Edge cases
I'm not convinced by the argument that if a line (such as a line for notability for some particular class of subjects) is ambiguous or hard to draw, then it's not worth having a line. Drawing these lines is precisely why we have mechanisms like VFD; I think the wrangling Wikipedia-style process for drawing ambiguous limits gives good results.
Deletion
Deletion is an unfortunate term. Deletion and transwiki-ing are the same thing, and they mean "this information doesn't belong here, because this is an encyclopedia." That doesn't mean it doesn't belong somewhere else. We have transwiki because Wikimedia hosts other projects, and so we can say (at the same time that something is deleted) that it belongs somewhere else, because we know something about those other places.
Deletion is a charged word that makes it sound like I want to destroy information. I prefer "exclusion." If I vote delete it doesn't necessarily mean I think the information shouldn't exist; just that it doesn't belong here and I don't (within the context of this project and its sisters) know where it should go.