Guten Tag World

Aaaarggh...that's the tough question ! I know I have to go through it, so I'll try my best.

Let's begin to say what it is not :

• it's not some weird typography on a wall
• it's not some html syntax to enclose content
• it's not directives you put in a http header

So what is it here ?
Well, in my last post, I gave some first hint : tags were described as both qualifiers and filters. Tags are stamped on content to qualify it; and then you use them to filter content.

I hear you say : "but it's just like categories".
No, it's not. Categories are pre-defined, you have to know beforehand the different categories that you will use. Likewise, everybody must have a clear view of what the category is describing to be able to use it. So there must be a consensus on what the category means, as a set of items.

Tags do not exist before you use them (you may use existing tags, but it's not necessary). Tags do not have to mean the same thing for everyone. You could think of tags as free, extensible categories that only the setter fully understands.

So now you think : "but how can it be of use if nobody understands the same thing and file things differently ?"
Well, the thing here is that we share some context that will give a clue to the meaning of a particular tag. What context do we share ? First, we are all humans, so we all have the same mind-algorithms ! Second, we share a language, that also has some context-driven meaning. Third, remember, I said a tag represents a subject of interest. So a subject of interest is a context.

Still there ?

Tags are freely chosen by their user and mean something to him, within a context. And that context is helping others understand the meaning of the tag. Let's take an example : You're moving to a new flat, and you ask friend to help you carry away boxes of various stuff. You decided not to use stickers (aka categories) to identify things within the boxes (there are too many), but you gave a pen to all your friends, so that they can decide what's inside and write it (aka tags) outside.

So they are free to write any tags on the boxes. When it's time to step in the new flat, and put boxes at the right place, anyone can carry boxes, so the bearer doesn't know who wrote the tags. Do you think they will be able to do the job as it should ?

Well probably so. By a strange mechanism, everyone will interpret tags in the context of moving boxes from a flat to another. And without stickers, most of the boxes will get to the right room. Maybe a tag will be hard to decide on, but then you can ask to the friend that wrote it. Is he gone ? Well, you could check how his tagging was like on other boxes, and get context about how he usually tag things. Is he very broad in his description (a man for sure) or very precise (a woman...) ?
Now you know, the tag becomes understandable, and you take it in the right room without opening.

So that was my example. Not the best, but mine ;-)

Tags are polysemous. They can perform several functions :

• Identify what it is about (eg : politics)
  
• Identify what it is (eg : blog)
  
• Identify the content owner (eg : bbc)
  
• Refine broad categories (eg : foreign affairs)
  
• Identify characteristics (eg : funny)
  
• Identify the tagger (eg : mystuff)
  
• Call to action (eg : toread)
  

Nevertheless, they have a meaning in the right context. How do you know the context ? Well it depends, but most tag-based services give you a basic context : all the tags that all users applied to a specific content. Different users have different contexts, but having them all allows you to infer what the tag is about.

Is that all there is to know about tags ?
No, tags have a lot of other characteristics ! But we'll come back to some them later on...

Hope this helps...