On Sat, 5 Sep 2009, Jonathan Wilkes wrote:

If you are making a tag system and are going to search by full tagnames, than each tag has better be a single symbol and each request better not contain commas. But there are things for which you'd search by text content, and people are using commas all over english text, so naturally, if the author field needs to be in plain english, it will need to be searched like plain english is to be searched.

I'm supposing that a tag system is something in which a tag is atomic (you don't search for substrings of tags when you search by tag) and in which tags are considered more special than the rest of the text, because else why bother calling it a tag system and why bother making it any different from a plain text search. furthermore, i suppose that there is an aim of semantic unambiguïty, that is, there is some kind of standard on tags such that either "fm" or "frequency_modulation" is used but not both because all synonymous words for 1 thing are represented by 1 tag.