From MIKE2 Methodology
Categories are the major topics covered by an article. Categories provide a useful mechanism for readers to find an article within a classification scheme. All articles should have at least a single Category.
Using Categories, users can find articles based on their area of interest in a fashion that is oftentimes more effective than using search terms. It also helps readers to find similar articles.
Category Concepts
Categories are simply used to make it easier to find articles and to relate them to one another. MIKE2.0 articles can appear in more than one category and each category can have more than one parent category.
Categories do not form a strict hierarchy or tree structure, but form what is generally referred to as a directed acyclic graph. For a more detailed description of Categories, refer to the article on Categorization on Wikipedia.
Implementing Categories
Adding Categories to Article Pages
Categories are added to articles by including the following text to the top of the Article: [[Category Name]]
An example can be seen by looking at existing Category pages.
Creating New Categories
Contributors can easily add Categories to their articles and create new Categories if they do not exist. Adding a Category tag to an article (as shown above) that does not exist automatically creates a new Category.
Contributors that create new Categories should add a description of the Category on the Category Page. This can include links to other articles that describe the Category in better detail. An example of Category Page descriptions can be seen by looking at Tools and Technique Papers.
The recommendations put forward on Wikipedia for using, creating and editing categories are well-defined. They provide a good set of guidelines for what can be an imprecise science related to the classification of articles and organizing categories.
Sub-Categories
Sub-categories are children of parent Categories. They are useful for organising content at more granular levels of detail under a major category heading.
Sub-categories are created by simply adding the name of the parent category to category page of child category. For example, the add Category:Architecture Design Patterns as a child of the Category:SAFE Architecture, the following text is added to the category page:
[[Category:SAFE Architecture]]
Although Sub-Categories are members of a parent it should be noted that the category scheme as a whole does not form a tree. Each article can appear in more than one category, and each category can appear in more than one parent category.
To see an example of a category with multiple sub-categories, refer to Category:SAFE_Architecture.
Category Extensions in the MIKE2.0 Wiki
Category Browse Extension
The CategoryTree extension provides a dynamic view of the MIKE2.0 wiki's category structures as a tree - it uses AJAX to load parts of the tree on demand. This allows users to more easily see the list of article by category and their relationships.
Category Select
This extension makes it possible to select categories from a "tag cloud" of all available categories as opposed to having to manually write the category name..
currently under development which will make it possible to add new categories to article pages through a drop-down list as opposed to manually writing in the category
Category Suggest
This extension
makes the category dynamically appear as it is typed by named as opposed to having to manually write the category.
Integration with Social Bookmarking
This extension enables bookmarked articles to be integrated to the content developed in a wiki through the use of common categories. This functionality is provided by an extension to the Scuttle Social Bookmarking tool.