If a question involves an expansion to a game, should the expansion always be tagged? What if the expansion is obvious from the question or title? Or, should expansions generally not be tagged?
My view is the more information the better. Some expansions can change the rules and tiles, options, cards etc of a game and can make an answer incorrect because of the amount of information supplied. Tags help to properly categorise the question and allow people to keep an eye out for, or ignore questions that they know they cannot answer.
So my vote would be yes, use tags as much as possible.
Tags are good for setting interesting and ignored tags, to have some questions highlighted and some greyed out. If someone is interested in Settlers of Catan, they might follow the settlers-of-catan tag. If, however, they have never played the Cities and Knights expansion, they might not want to bother reading questions involving it, and so set the cities-and-knights tag to ignored. That way, they can quickly scan the questions, paying particular attention to the the Settlers questions but being able to see that they can skip the ones about the Cities and Knights expansion explicitly.
Tags can also be helpful when someone wants to look for questions on a particular topic; they can browse questions tagged with that. If you just put the expansion in the title, and don't tag it, then it won't show up in that list when people are looking for it.
So, I'd say that if the question is about the expansion, and can only be answered with knowledge of the expansion or is only of interest to someone who wants to know about the expansion, then tag it as such. If it's just a general Settlers question, that might happen to mention the expansion in passing, then it doesn't need to be so tagged, though depending on the context it might be useful.
But yes, do tag with expansions, even it it's obvious from the title.
Understanding that this is an old question ... a consistent direction across Stack Exchange sites is to use as few tags as possible, keeping in mind that this is not always followed, particularly on the original trio.
One issue with adding tags is that they can easily become redundant. Take seafarers-of-catan, for example. All seven questions so far are also tagged with settlers-of-catan ... the only thing we gain right now by using the expansion tag is the ability for people to follow it, and only 5 are following Seafarers so far. catan-cities-and-knights is the same: 9 questions, all also tagged with Settlers.
Part of the problem is that there are few questions about expansions that I can imagine that don't also involve the base game. If every Seafarers question is also about Settlers, do we accomplish anything by using both tags?
The other part of the problem, I think, is that we don't have any "series" tags, so questions about a family of games are lumped in with the original game, and we end up with a number of questions that are, in effect, "randomly" tagged: they may apply to other games in the series as well, but aren't tagged that way because the OP doesn't have them ... and if we tag with each expansion, eventually we'll run out of tags.
See these questions as examples:
- Fixing warped board pieces - applies to all Settlers sets
- Can You Buy a Catan Border That Fits? - same
- Is drawing resources required? - specifically asks about Settlers, Cities and Knights, and Fishermen, but isn't tagged with Fishermen
A settlers-of-catan-series tag would make it easier to tag questions like that.
I guess after thinking it through, I support Brian's position with a few suggestions.
Questions about a single expansion
- Do tag with the expansion, even if it's included in the title. Tags should be the primary way to follow games/expansions; having the game/expansion in the title is fine if it's worked in naturally, but don't write "Seafarers - does such-and-such apply?"
- Don't tag with the base game. The assumption is that all questions tagged with expansion Y are saying "expansion Y as part of base game X".
Questions about multiple expansions and the related base game
- Don't tag with expansions.
- Don't tag with the base game.
- Do tag with the series.
Of course if that turns out to be the consensus, we would have to determine how to create series tags, and like on Gaming, that will create some issues. settlers-of-catan-series works fine, battlestar-galactica-series is too long. (25 characters is a hard limit and is unlikely to be changed sitewide.)