Tagging has been around a while now, but we still don’t seem to know what it is. Some people argue that it is the complete opposite of categorizing, while some believe that tagging shares much with categorization. I go even beyond that, and I have argued in several publications that rich structural information can be extracted from tags, if we know where to look.
But why does it matter what tagging is? Can’t we go on tagging even if we don’t really know what we are doing? (Works well in the rest of our lives!)
Well, yes, we could go on tagging. The question is what to do with the tags once we have them. If tags are really not categories, and if the extreme view is right that they are simply some sort of completely individualistic associations, then it seems to me that we can’t do ANYTHING with them across the user base. If on the other hand there is some agreement between users about basic categories at least, then we should be able to aggregate them accross users and use them in interesting ways.
The fact that we already do aggregate them and interesting patterns of popular tags can be found, suggests to me that the extreme view against tags as categories must be wrong.
Csaba's Blog 
Tags are mere terms, phrases. If you want to categorize, you may use tags as names for categories. But tags, as names for categories, do not have to be identifiers, and usually are not:
– the same tag may be used (by the same person or by different people) to tag items that are seen by the taggers as belonging to different categories;
– different tags may be used (by the same person or by different people) to tag items that are seen as belonging to the same category.
In a system with a controlled, unambiguous dictionary, you could identify tags with categories. This would still be a simplification, though.
The questions are (among others):
1. When we tag items on the web, do we do so with some categorization in mind, or not? That is, does tagging reflect categorizing?
2. Does the fact that we mine interesting patterns from popular tags prove that tagging reflects categorizing?
As for 1., it may be hard or even impossible to judge in general, but I would guess that tagging does reflect categorizing. At least when I assign a tag, it is because I find the item in question belonging to some particular category.
But we can’t exclude that there are some who assign tags based on some obscure motivation not related to categorizing.
As for 2., it appears to me that even if tags were assigned completely randomly, without any categorizing in mind, we could still mine some interesting patterns, just by chance. On the other hand, that we do not see any interesting pattern emerging for some tag, does not mean that there is no categorizing intended; it may be that the way we (the miners) categorizes is so different from the way they (the taggers) categorize that we are simply not able to see the pattern which is there.
This is of course philosophizing, and it seems plausible that most people do categorize while tagging. My major concern with tagging flows from that tags themselves are not categories, but rather names, and that synonymy and homonymy seem to unnegligibly interfere, in some cases, with the use of tags for practical purposes.
vQ
Interesting comment, thank you. Just to clear things up a little, I am not claiming that ALL tags are category labels. A tag like “interesting” is clearly a property of some sort, and it is very likely that tags like that will be used as you suggest.
On the other hand, I am not as convinced about the strong distinction between “categories” and “names for categories”, as you are. There is of course A LOT of work done on this subject by cognitive psychologists (and philosphers, if you insist!)
One of my favourites is Ellen Markman. Another is Paul Bloom. What do you think of this:
http://faculty.virginia.edu/childlearninglab/research_interests.php
http://links.jstor.org/sici?sici=0009-3920(199010)61%3A5%3C1461%3ANMCRTA%3E2.0.CO%3B2-N
And of course:
http://www.bbsonline.org/documents/a/00/00/04/32/bbs00000432-00/index.html
Use tinyurls, pleeeease!
The first seems to differentiate between categories and category labels. The other speaks of categories and terms. (And refers to my favourite Quine.) The last speaks of categories and words. (Be careful not to confuse the categories named by general terms, and the categories to which the terms themselves belong, either syntactically or semantically.)
No one of them seems to confuse terms (words, labels, names, tags) with categories.
I would actually be close to claiming that all tags are (used as) category names, unless they are assigned on the basis of some process that either picks them randomly, or with no connection with the content or form of the tagged item whatsoever (and thus randomly from the point of view of tagging the item).
If one reads (watches, tastes (?), whatever) an item and assigns to it a tag based on that experience, it reflects some sort of categorizing, unless the tag is intended to be a proper name. (But who tags items on the web with proper names? Well, in principle not impossible, but unlikely.)
Consider the tags ‘poor’, ‘super!’, ‘me’, ‘dogs’, ‘ghrrr’, etc. Unless used as proper names for items on the web (e.g., this picture has the name ‘poor’), they seem to name categories — those of poor items (in whatever sense), of super items (…), of dogs (perhaps rather of representations of collections of dogs, rather than of individual dogs, such as a picture of two dogs, but not a picture of one dog), of whatever makes the author make the sound ‘ghrrr’, etc. ‘Me’ is an indexical, and while you could claim that it is used as a proxy for a name (it names an individual), in the context of items on the web it would rather name a category of, e.g., pictures of the author (thus ‘me’ is actually shorthand for ‘picture of me’).
What do you mean by ‘property’? How can a tag — a syntactic element — be a property? You seem to use the term ‘property’ with a non-standard way. There is hardly an agreement in philosophy as to what properties are (see, e.g., http://plato.stanford.edu/entries/properties/; they speak of property words, words denoting properties, but not of words as properties), but there seems to be no confusion of words with properties, at least.
🙂
vQ
See http://plato.stanford.edu/entries/categories/ and related entries for more on categories.