Robert Bilhmeyer wrote:
"Proper" categories like [[Computer science]] are best represented by dividing the listing into subfields (as done in the current page). Magnus's scheme could support this via more complicated syntax (e.g. {{{CATEGORY P.M. of Great Britain;1985}}}, or {{{CATEGORY Comuter science;Algorithms}}}), but that reeks a bit of overengineering.
My experience from various wiki shorthand notations is that they should be easy-to-write. The major difference between an old style website and a wiki is that the wiki is written by all, and that this broadening of the authorship must be met by a simplification in format. For example, the choice between plural and singular in article headings is guided by which is easier to use as a link from another text, and that most often turns out to be a singular, thus [[Car]] rather than [[Cars]].
The indicated sort of overengineering should be avoided, not because I say so, but because it will not be used. You can try to introduce it, and then collect statistics on its use, and draw conclusions from the numbers. Keep it simple, make it successful. Even the use of special {{}} braces seems overly complicated to me. This is not a programming language designed for programmers, but a text format intended for someone who is specializing in entomology or woodcarving.
For a real simple category system, see http://www.c2.com/cgi/wiki?CategoryCategory