Tagging is the a way of labelling something, such as a website, an article on a blog, a photo, video, or any other object. By tagging things you group them together. This makes them easier to find.

You may not realise it, but you see examples of tagging every time you go shopping. Go to the supermarket to buy milk, and you'll find cheese and butter nearby. That's because all those items have been, in effect, tagged with the term 'refridgerator'.

In another example, I was watching an episode of Numbers recently, and Professor Epps mentioned that a supermarket analysed its sales figures, and discovered that sales of nappies (diapers) peaked and troughed in synchrony with those of cartons of beer. They drew the conclusion that men who were sent out to buy extra nappies were taking the opportunity to buy extra beer, so they placed the items next to each other and sales of both increased. I'm not sure if that story is actually true, but it's a nice illustration of the concept of tagging because both of these items were, in effect, tagged with the label 'items bought by men sent out to buy nappies"!

Now, you might say we don't need tagging in the context of technology, because we have categories. This article, for example, has been published in a category called 'Web 2.0'. Why give it a tag as well?
The trouble with filing things in categories is that, as a rule, you can only file them in one category, whereas they could, logically, be stored in a different one. This restriction does not apply to this blog, because Squarespace lets you place articles in more than one category at a time, but it was certainly the case with my original website. If I'd been writing this article for that website I'd have to choose between the following categories:

Web 2.0, because this is about Web 2.0;
Using and teaching ICT, because it's about using an aspect of ICT;
Leading and managing ICT, because it's aimed at helping colleagues understand an aspect of ICT, which is one of the things ICT leaders and Co-ordinators tend to do.

None of these is inherently right or wrong, but whichever one you choose precludes the others. If you forget where you 'filed' it, or if other people don't think in the same way you do, the article will, to all intents and purposes, be lost, because nobody, including you, will be able to find it!

There was a marvellous illustration of this many years ago in one of the Professor Branestawm stories (I've included a couple of these books on my Amazon Books page).

Professor Branestawm, as the name implies, was an absent-minded professor. In one of the stories, he borrows a book from his local library, but 'loses' it. So he borrows the same book from another library, and then 'loses' that. Eventually, he has borrowed the same book from over a dozen libraries, and spends all his time cycling from one library to the next renewing the one copy he has managed not to lose, in order to avoid paying a fine for late return of the book. In the end, he decides to come clean and so he invites all the librarians round to his house so that he can tell them all that he has lost their books.

While they are waiting for him to appear, they browse his bookshelves, and start to find their books. What had happened was that Professor Branestawm had filed the book in different sections of his library. I can't recall the exact details, but it was something like this:

One copy was stored under B (for biology). Another was stored under 'P' (for plant). Another was stored under 'T' (for tulip). You get the picture.

Now, that's quite humorous on one level, but at a deeper level it illustrates perfectly the problem with hard and fast categorisation.

Tagging cuts across all that - in fact, you might want to think of it as a kind of horizontal categorisation rather than a vertical one.

Take this article. It's tagged with, amongst other things, the term "Web 2.0". That means that anyone searching this website on the term "Web 2.0" will find it. They will also find other articles tagged in the same way, along with any videos, photos or podcasts I happen to have given the same label too.

I've also tagged these articles with the term "Web 2.0 for Rookies", which means that if you look for that tag you will see all of these articles bunched together. In fact, in a Branestawm-like fashion, I'd completely forgotten this, and have been advising people to search for these articles in the alphabetical index! It was only a message in Twitter from Sandy K giving the tag URL which made me remember! (You can follow Sandy on Twitter.)
There are some things you need to think about when it comes to tagging.

Firstly, you have to be consistent, even down to deciding on what case to use. For example, I discovered, by accident, that the tag "Web 2.0 for Rookies" is not the same as "Web 2.0 For Rookies" (spot the difference!). If you're not consistent, people, including yourself, will not be sure what to search on and will still have difficulty in finding articles.

Secondly, this has an implication when it comes to working with colleagues and students. Do you allow them to create their own tags? If so, should there be rules about tagging to ensure consistency?

Thirdly, bear in mind that tags need to be specific enough to filter off irrelevant search results, but not so specific that people would never think to search on that term. An example of a tag that would not satisfy the first condition would be, on this site, ICT. Given that every article is about ICT in some way, searching on that tag would bring up the entire collection of articles! At the other extreme, a tag like "Terry Freedman's article about tagging in his series about Web 2.0 for rookies" would be as much use as a chocolate teapot because nobody would ever think to use it.

Fourthly, how far should you go in tagging? I know that some people recommend tagging articles with every conceivable label and variation they can think of, in order to maximise its chances of being found, and of being picked up by search engines. It's up to you whether or not you adopt that approach. Personally, I find it boring to spend ages tagging articles, and I've found that tag generating applications are so 'efficient' that I have to spend ages weeding out the ones that I don't think are that useful. Aside from all that, I simply don't like the fact that having loads of tags at the top or bottom of an article takes up so much space!

Used well, tagging is a perfect example of a Web 2.0 'application': it's very effective in linking up disparate objects, and therefore people, as will become apparent in the article on social bookmarking. And it's conceptually simple. What more could one want?

Have you seen the other articles in the Web 2.0 for Rookies series? Feel free to comment, and to recommend them to your colleagues and students.