Categories and Tagging - What's it all about, Maccie?
What is tagging? - A Definition
Tagging is a means of organising content, a few key words or phrases are associated with a piece of information that are common to other pieces of content on similar or overlapping topics.
What, why, and buh? - An Organisation Introduction
One of the key features of what has become known as "web 2.0" is the meme of user-generated, shared content. Whether this content be webpages for images users have created, essays or stories they have written, music they have composed, or even diary entries they have posted - "blogging" - a vast amount of material on many different topics is published in one on day on any number of websites.
The key to making sense of this data, and to finding the information you want, is through categorisation. Content is differentiated by topic and grouped by similarity to improve its accessibility.
Categories, furthermore, may be subdivided. If we consider we are organising a list of recipes, we may be inclined to divide them by course - appetiser, dessert, and main, for example. It may be more constructive to further break down the recipes in "appetiser", however, into, say, "soups" and "salads". Appetisers that fall into neither category can remain in "appetiser" and neither of the sub-categories.
However, a browser of our selection of recipes may be inclined to search for fish dishes, which may be main courses or appetisers, depending on the recipe. We could cross-reference our categories by course with a selection of categories by main ingredient. As much as a browser may wish to pursue our recipes by ingredient, they can by course.
Equally, though, a user may wish to browse by the cooking time required, the cookery expertise required to prepare the dish, etc. As we seek to cross-reference more and more, it becomes ungainly to consider the information filed away in labelled card folders, or present in a grid as above.
Computer processing power allows us to do away with this metaphor for categorisation - we can merely identify some of attributes of a piece of data - website content, if you will - and have the server create an index of the content when we choose to pursue by any such attribute.
This is called tagging. For example, we could tag - that is to say, associate keywords with - the recipe for Seafood Risotto with keywords such as "rice", "fish", "main", "advanced", or even, "absolutely delicious if you get it from that restaurant on the seafront at Anzio".
Consider tagging like an extensive system of labelling. All items labelled with a specific phrase can be retrieved immediately, it is not necessary with modern computing to introduce the idea of categories as folders into which content is distributed - a hierarchy, if you will. Instead, the visiting user can choose to view all the pieces of content sharing a specific tag, and sort by any number of options. This is much more flexible to the user's needs.
What tags should I apply to my content?
Tags should summarise the nature of a piece of content - be it blog post, photograph, etc. It needn't completely described, but someone reading the tags alone should be capable of getting a rough idea of what content is about.
Whether to keep the tags singular or plural is a matter of personal style, but it should be a consistent system - if one article on spanners is tagged with "tool", one on screwdrivers shouldn't be tagged "tools". This ensures that similar items can be found with greater consistency.
A good mindset to assume when tagging content is that of "how would a visitor get back to it?". If a pursuer returns a few months down the line, desperate to pull up a piece of content for a friend, what parts of the content would stand out most?
Who uses tags?
Tagging is the categorisation system of choice for the majority of the blogging world. It is also used by websites such as Gmail to assist users in organising their mail - under the name "labelling" - and is prevalent on sites such as Flickr and Last.fm, early and classical examples of Web 2.0 websites.
How to instigated a tagging system?
If you are using an account on one of many popular user-generated content websites, then they may likely have a tagging system already available to you.
If you wish to develop a tagging system of organisation for your own website, you need to approach it from the point of view of each tag being associated with a list of files. When a file is displayed, all the tags that link to it - that is to say, every tag in which that piece of content is referenced to - are retrieved. When a user is sorting by tags, all the files that that tag references must be retrieved.
The exact algorithm design is beyond the scope of this brief 101, but you may find help if you are having trouble in the databasing and server-side programming sections of the forum.
This guide describes instigating a tagging organisation system to one's local file system, which serves for interesting reading and may help give you an idea over how to develop your web-based tagging system. This thread on tag clouds - see below - also includes a model of how to instigate such a system, courtesy of Horus_Kol et al.
How is tagging represented?
On a specific piece of content, the tags associated with it are usually expressed in a simple list, with a clear separator between different key terms - e.g. a comma. One of the more striking ways of displaying tags, however, is through a weighted list.
A weighted list is where list entries are given different formatting - font weight, font size, font colour, etc - based on their relevance or importance in the list. A weighted list of tags, for example, would show the most relevant tags to a piece of content as being much clearer and well-defined than the least relevant tags.
Graphically, a weighted list may be shown as a "tag cloud".
This was meant as a brief introductory essay to the topic (although, do not get the impression that I am some sort of expert on categories... I do go outside, you know) - in the spirit of promoting discussion, please do add/correct/comment/rebuff . What do you think about tagging? Seen any clever implementations of it?
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:MACBETH IN SPACE: "He's had a fair bit of practise at this snice[sic] McDuff[sic], you know." - LP :NOW WITH TWO REFRESH BUTTONS:
I've recently found myself back in an SEO role. Blogging was fairly new to our company when I had transitioned out of it a few years ago. Now playing catchup, especially on all the new social media components of SEO. Thanks for the explanation on tagging.
Seems like from an SEO perspective, tagging can provide your blog with more unique pages (reshuffling of content). I would imagine these groupings of posts could provide good benefit to SERPs?
. What do you think about tagging? Seen any clever implementations of it? 
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