tags and categories

What is the difference between categories and tags, when would you need to use them, and what for? Would you ever need to use both at once? Within the context of blogging and, more broadly, the web, I’ve found myself explaining how to use tags and categories a few times in the last year. For this reason, I think it is a good idea to take a moment and document which principles I use to guide the creation of both and how to use them in a couple example scenarios.
First lets define categories and tags. Categories are defined as a division within a system of classification. Tags are keywords that are assigned to specific items, such as blog posts. We can already deduce two things from these simple definitions: categories require a system of classification for content, so you must have some context for your application of the term; tags require content on which they are based. In other words, content fits into categories, and tags fit the content. One is top down, the other is bottom up.
Lets use an example that could use both tags and categories at once for different purposes. If you are looking at MetroCascade‘s feed aggregator, you’ll see that have a system set up which pools new information brought in from sites that have RSS feeds for the Victoria area. Simply put, this is a hot spot for new information that is geographically relevant to the 250 area code.
Three questions which I would ask are:

  • Who supplies this content?
  • How will it be sought?
  • What is the information about?

Categories and tags define and eventually answer those questions.
For MetroCascade I would see it most optimally set up this way:
Categories: News (Authoritarian – very high traffic – for seekers of current events in the area) , Blogs (Personal, lower traffic – for community and interest)
Tags: Dependent on content provided. Tags should always be content-maker defined as the writers will always understand the key words best through intent.
Tags will cross over between categories, so a tag search for “inner harbour” would show blog posts about the inner harbour as well as news. The distinction about categorizing the feeds into News and Blogs is most important for the kind of aggregation options that will be given to end users. If a user wanted to be a part of the Victoria blogosphere, but did not want to be pummeled by the local news stories, they could simply view the blogs category. Subjects would change, tags would go all over the place (as they might with news, if news organizations actually took the time to tag – some do), but at the end of the day you’d have a useful distinction of information through categories which catered to the nature of the source and the intended audience rather than the subject matter itself. Subject trends will emerge through things like tag-clouds. This allows for subject matter to flow freely, yet remain quickly accessible through the tag link drill-down.
Another quick, more tangible, example. Imagine you ran a library. You will have two master categories: fiction and non-fiction. Subjects, or tags, like “sports, dragons, politics, mathematics” may branch into both or only exist in one category. You could have a sports book on how to coach tennis, or a sports book on the story of a tennis star who summons the power of a volcano to win the Elbonian Open. One is factual, the other is fictional. They both have subject matter relating to sports and, more specifically, tennis. Why does this matter? Because eventually you’re going to have to put the books on shelves and a tennis coach should be able to easily come in and find resources. Likewise, someone who wants to be entertained should be able to go to another shelf and not find themselves reading about the importance of pronating their wrist while serving. There is a fundamental need for the distinction, and its root lies in the understanding of how information is to be sought and used.
In conclusion, categories are rigid and tags are organic. Usually you will want someone who has a 40,000 foot view to control categories, and tags will be assigned over time through contributors.
How do you use categories and tags to organize your information?

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