Let's start with an example this is used as a hybrid combination of and . Most, if not all, questions with this hybrid tag have both these other tags any way.

It seems needlessly redundant to have questions tag and as well as . It results in a very specific tag, which does not offer much. If somebody wanted to search for questions/answers on both 'android' and 'sd-cards' they can simply search for both.

I would suggest that this tag, and similar tags be removed and their use stopped. Either that, or I shall start using tags such as


Yes, there are certain use cases where a 'hybrid' tag provides more then just two tags for one. Answers have already made solid cases for their usage. So let me say I am focusing on tags that are not much more then two tags combined into one. Please do not get too caught up in the example I gave. Please do take note of my hyperbole.


The focus of this question is not this specific example, but the general practice. Yes, I do still think that is a 'hybrid' tag, but the question is about if this style of tagging should be permitted in the first place. If these tags are to be considered bad, as a separate question we can discus this example I have provided.

  • I've added a "NOT" into the title, so that I can — in good conscience — upvote your post. I also left you a little present. – Lightness Races in Orbit Jul 26 '13 at 14:40
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    haha I broke stackoverflow.com/questions/tagged/… by removing android-sdcard from the 5 posts on the first page of 663 posts. It hasn't repaginated, and now there are no posts and no page navigation. – Lightness Races in Orbit Jul 26 '13 at 14:42
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    Seems like you should wait to do anything like that until there's a community consensus on the subject, no? – Joe Jul 26 '13 at 14:44
  • @Joe well of course, that's why we discuss things first. – thecoshman Jul 26 '13 at 14:45
  • @Joe: I didn't block any tags. I merely used my editing powers to -- in my eyes -- correct the posts. Feel free to roll back the edits, but I have no doubt that those posts were mistagged. At the very least, they weren't tagged android. (Strictly speaking, though, you're probably right that I should have left it since we're now engaged in a debate on the topic.) – Lightness Races in Orbit Jul 26 '13 at 14:46
  • I noticed a slew of these re-tags in the review system this morning. I skipped all of them because it seemed weird to me that there were so many, and I have a limited ability to judge whether the sdcard piece truly belonged as a hybrid tag. – jwiscarson Jul 26 '13 at 15:49
  • Looks like @ChrisF agrees with your proposal, considering the tag he removed. :-) – Cody Gray Jul 26 '13 at 15:56
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    @CodyGray - the tag was meaningless given that we can't have a single tag to replace discussion and tags as there has to be one required tag. – ChrisF Jul 26 '13 at 16:09
  • @ChrisF a) I didn't add that tag b) consider it part of the example, and so please replace – thecoshman Jul 26 '13 at 18:29
  • On a related note, I wonder if the hybrid tag android-screen is necessary at all. – Old Checkmark Jul 29 '13 at 7:54
  • @OldCheckmark I would imagine not, but please, this is not about specific tags, but the general concept of 'hybrid tags'. Feel free to post a question specifically about that tag, I suggest you link to this one for discussion of the general policy with hybrid tags, keeping your question specifically on whether or not that tag is such a hybrid. – thecoshman Jul 29 '13 at 8:07
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    The problem is, that without hybrid tags, you have a lot of meta tags, which itself have completely no meaning. For example, IO is a great example of very poor tag. But java-io or python-io are very informative. Going further, imagine [2] tag for version 2. Instead of having [jsf-2] tag, you tag your questions with [jsf] and [2]. The number of tags diminishes, the chaos takes over. – Danubian Sailor Jul 29 '13 at 14:16
  • @ŁukaszLech I see what you are saying, but those 'tags' you listed do not make sense on their own. a 2 means nothing, so shouldn't exist in the first place. What you have done, is taken valid tags, and broken them down into parts that no longer make sense, I could take 'Boost' and break that down into 'Boo' and 'st' – thecoshman Jul 29 '13 at 14:41
  • @thecoshman it's a bit extreme, but it's the same operation as you have proposed with sdcard. [sdcard] itself as the tag does make as much sense as [io], because it can't be used separately on SO. – Danubian Sailor Jul 29 '13 at 14:50
  • firstly, please try to avoid getting caught up with this exact example, I have already state this question is to focus clearly on the handling of hybrid tags. I believe you have got the question backwards. I am not proposing that tags be broken down all over the place, I am saying we avoid sticking tags together. Please read my question for an example (warning, hyperbole). both 'sdcard' and 'android' are valid tags on their own, else they should not exist. I am thus opposed to them being used in one 'android-sdcard' tag, though again, please do not get caught up on this example... – thecoshman Jul 29 '13 at 14:55

The idea is very good, however some tags can have different context when used in conjunction.

Look for example at boost and exception:

  • means questions related to boost
  • means questions related to exception handling
  • means questions related to Boost.Exception library
  • means questions that use boost and exceptions, but not necessarily boost exceptions.

Thus when doing such a cleanup, you would have to verify if the hybrid tags removal wouldn't remove some important additional information.

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    Yes in this case the boost- in boost-exception disambiguates the tag, since the "Exception" in "Boost.Exception" is quite different from "the common programming feature called 'exceptions'". It's a proper noun, for one thing. However I'm yet to be convinced that there is anything inherently Android about the SD Cards used in Android devices. – Lightness Races in Orbit Jul 26 '13 at 14:45
  • Agreed, there are a few exceptions where a 'hybrid' tags actually helps to disambiguate things. – thecoshman Jul 26 '13 at 14:46
  • Why don't we just require users to know what they're asking about? – Trojan Jul 27 '13 at 3:49
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    @trojansdestroy oh sure. hey, here's another idea, why don't we require users to know the answer already, then we don't have to bother answering them. – thecoshman Jul 27 '13 at 9:44
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    @thecoshman I'll make my sarcasm more blunt and less possibly naive-and-actually-serious next time – Trojan Jul 27 '13 at 9:49
  • ooh I see... I guess I should signify in some way that I found this mildly amusing... – thecoshman Jul 27 '13 at 9:51
  • @thecoshman Your response didn't indicate that you found it amusing at all. Did you really? FWIW, I agree that some hybrid tags are beneficial, and combining their component tags should be a high-priority goal. It's interesting to me that people can come up with the individual tags that make up what they're getting at, but don't think to combine them (and the hybrid has to show up at least some of the time). – Trojan Jul 27 '13 at 10:04
  • [exception] is a meta tag and I think it should be burninated... and it's not burnination request yet... – Danubian Sailor Jul 29 '13 at 14:51
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    @ŁukaszLech how is it a 'meta' tag? It can be used for any questions on exceptions in general. Combined with a language tag (a second tag) such as c++ you have a question about exceptions in C++. The problem with hybrid tags is people who would instead tag this question with just one tag c++-exceptions. That hybrid stops people seeing that question as a 'C++' question. That is the problem with hybrid tags. – thecoshman Jul 30 '13 at 7:39

I think this would need to be examined on a case by case basis, and sometimes there is a purpose to the hybrid tags.

I think hybrid tags need to be evaluated on a case by case basis.

  1. Do they identify a field of expertise or interest that is not of fully of interest to one or more of the component parts?
  2. Do they identify a unique field of interest or expertise?

First lets try an abstract example...

Lets think about , and the potentially hybrid tag .

I would argue that the latter is more than just the sum of +.

The resulting field is more than the sum of it's parts. Sure somebody could find questions related to motorcycles by combining the tag, but to do so you abuse the scope of the more specific tags. The area of expertise for motorcycles is not just make up of folks that know about engines and folks that know about bicycles. In fact being an expert in one or the other of those other tags probably specifically mean you are not interested in questions about motorcycles unless there was a specific aspect of the question that was a cross over issue.

To the motorcycle expert looking for questions he could easily find the right ones if he knew that a combo was what was required. However for the mountain biker enthusiast having motorcycle questions in their feed would be unwanted noise, as would having questions about disk brakes in the feed for the diesel engine mechanic. Only having the hybrid tag keeps the respective areas of expertise/interest duly separate.

In this example, having a tag would preclude the use of or on all questions about motorcycles except as they were specifically related: a question about how motorcycle engines work might have and a question about whether rules of the road are the same for cycles as motorcycles might have .

Back to your specific example...

I think your specific case study is an analogous to my fictions example.

Knowing a little bit about Android and its SD Card system, this is almost a different beast than standard SD Card issues. Experts in SD Card issues across multiple platforms would be baffled by the kinds of issues raised by android users because they are operating on a layer of abstraction not normally present. In this case I think it makes sense to specifically identify them as their own subset, not just by the union of two other tags.

The tag might be used in combination with but using for questions that were about Android's sdcard access api would not be appropriate as that is really a separate unrelated area of interest.


There are some hybrid tags are not backwards compatible with the composite parts. They are a field of their own that is more than the sum of their parts. They are likely not of interest to one or more sets of experts that cover the à la carte tags.

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    A question tagged android,sd-card is quite obviously about the use of SD Cards on Android. No need for hybrid tags with all the problems they bring. Unless "Android SD Card" refers to some Android-specific interface layer, and not SD cards themselves, in which case the tag wiki needs to reflect that (and the questions need to be tagged both android and android-sdcard). – Lightness Races in Orbit Jul 26 '13 at 15:05
  • Yes, I really should of said in the question, I do see the use in certain use cases for hybrid tags. And perhaps this is a valid use case, but lets try no to focus too much on this example. I feel your abstract example is some what missing the point. Those two tags together does not change, it would be 'bicycles with engines' and frankly, I would still consider that better covered by the two tags in isolation. – thecoshman Jul 26 '13 at 15:05
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    @LightnessRacesinOrbit That's actually true if what you are looking for is questions about the android sdcard system. The problem is that puts questions that really don't have anything to do with a generic field of sdcard expertise in front of people following the sdcard tag. – Caleb Jul 26 '13 at 15:09
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    If someone wants to, they can filter for 'sd-card' and ignore 'android'. Job done. No silly extra tags. If the UI is not easy enough to use for this, then that is the problem. – thecoshman Jul 26 '13 at 15:11
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    @thecoshman If you didn't get my example I suspect you are looking at this only from one side of the coin. To the motorcycle expert looking for questions he could easily find the right ones with the tag combo. However for the mountain biker enthusiast having motorcycle questions in their bicycles tag feed would be unwanted noise, as would having questions about disk brakes in the tag feed for the diesel engine mechanic trying to follow engines. Only having the hybrid tag motorcycles keeps the respective areas of expertise/interest duly separate. – Caleb Jul 26 '13 at 15:12
  • No, I got your example, I just didn't think it the best. Take 'brakes' 'disks' and 'disk-breaks', that 'hybrid' tag is something distinct form the two tags it 'combining'. Technically a hybrid, but it is a very distinct thing, a general concept (brakes) and an actual implementation of that concept (disk-breaks). (Again, hard to make good examples here, as 'disks' would mean nothing as as tag by it self... well, depends on context I suppose) – thecoshman Jul 26 '13 at 15:15
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    I think the difference in your example and the one discussed in the question is that "motorcycle" and "bicycle" are actual words that represent a unique and specific concept. You can't readily separate them into their constituent parts. Those are precisely the cases where "hybrid" tags make sense (although they're not really hybrids then, I would contend). That's very different from mashing up two distinct concepts, however related they might be. – Cody Gray Jul 26 '13 at 15:58
  • @CodyGray I see what your saying in that example, but if that's the argument to be made, I would argue that "android-sdcard" is not a hybrid tag at all but a very specific one about a specific API. In the same way you might have a question about google reader that was not about rss, there will be questions in the android-sdcard tag that are not about sdcards. – Caleb Jul 26 '13 at 16:05
  • As long as you can search for both android and sd-card, and you can also search for sd-card and remove android results if they're really bothering you so much — and both these things are true — then there is no upside to hybrid tags. OTOH there are plenty of downsides. It's really a no-brainer. Read a book about database normalisation: with usability taken care of (see a few sentences back), the arguments are all the same at this point. – Lightness Races in Orbit Jul 26 '13 at 16:14
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    The downside is that you have to remove android results (etc.). When there is a possibility of having a simpler user interface without losing significant power, the answer is usually simpler is better. – Joe Jul 26 '13 at 16:16
  • Your answer here @Caleb seems to have focused too strongly on the one example I provided in my question. I fully accept that there are some certain examples of 'hybrid' tags that make sense. Frankly I still think, as Code Gray pointed out, your 'motorbike' example is not that good as 'motorobike' is not just 'motors' and 'bikes' together. – thecoshman Jul 26 '13 at 18:36
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    @Joe Picture this flow. "I want to see 'sd-card' questions/answers" <searches sd-card > "hmm... lot of Android specific questions here" <sets ignore for android > . Similarly, picture this "I want to see 'sd-card' and 'Android' questions/answers" <searches android and sd-card > NOT <searches android-sdcard > . I find it very hard to believe someone really default to trying a hybrid tag. Tags are basically keywords. Now, again, in this case maybe, maybe, 'Android-sdcard' is a suitable hybrid, but it is not that specifically I am questioning. – thecoshman Jul 26 '13 at 18:40
  • @Caleb I have now updated my question to state a very clear focus, this does somewhat invalidate most of your answer I am afraid, but hopefully it will help us be more fruitful with our time. – thecoshman Jul 26 '13 at 18:48

This seems to go against what we have been doing over a long time. We seem to want to remove meta tags so that each tag has an exact wiki defintion. the latest I have seen is here and here and many others

And even more clearly opposing this idea the discussion here


I think hybrid tags are useful in most cases, including the one you list. It must depend primarily on the user base; is it useful to see all SD-Card posts when developing for android with SD cards? If it is, then two tags is better. If it's not, then the hybrid tag is better, as it lets you instantly see only the posts that will be relevant to you.

While you could certainly search for the two in one search, if there's little reason to, then the hybrid tag is simpler. In some cases I could see justification for both the hybrid tag and the separate ones - if an android SD card question might be helpful to an SD card developer; in other cases if the separate tag isn't very useful and/or the question wouldn't apply to anyone searching for just SD Card, then it shouldn't be used as well.

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    You can search for posts with multiple tag criteria. Normalisation principles suggest that this is far superior to creating endless hybrid-tag permutations. – Lightness Races in Orbit Jul 26 '13 at 14:44
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    You missed my point entirely. There is no need for such hybrid tags, bar very rare execptions. – thecoshman Jul 26 '13 at 14:44
  • You can certainly search for multiple tags; that is addressed in my answer, after all. This is not a database issue, but a user interface issue; simpler user actions (not having to search for two tags, allowing users to search by clicking on a tag, etc.) should be the design goal in a user interface. What harm is done by having all three tags? Very little, except for improving the user experience. – Joe Jul 26 '13 at 14:46
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    Nonsense. Now a user has to search for "<<android> and <sd-card>, or <android-sdcard>>". How do you propose that they do that? You might as well suggest that calling the tag "a" is more user-friendly since there's only one character to have to bother to type. No, by constrast, intuitive usability flows from intuitive data management. – Lightness Races in Orbit Jul 26 '13 at 14:47
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    No, because we end up with three tags, two for the actuall question, "android, "sd-card" and one meta-tag that says it is both those tags at the same time. If this is a UI issue, then a UI tool should make it easier to search for both tags at once... oh wait, it already does. – thecoshman Jul 26 '13 at 14:48
  • If posts about SD Cards in the Android environment are all tagged android-sdcard, then that's all the user has to search. Like I said, this is not 100% by any means (and I am not an android or SD card developer so this particular example could be poor); but if Android's SD card issues are typically not related to other SD card issues, it seems silly to tag them with sdcard at all. – Joe Jul 26 '13 at 14:50
  • @Joe: That's great when the user already knows that, for this topic, the tag to look for is android-sdcard, and doesn't try to find them under the more intuitive android. It also breaks down when people don't use your hybrid tag for every pertinent post, which will never be the case. There is great power and expressiveness in using multiple tags to build up a list of relevant terms for your single post, and this should be celebrated by its use. – Lightness Races in Orbit Jul 26 '13 at 14:51
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    @Joe you seem to be forgetting about users who subscribe to tags. If any question related to any aspect of Android use the Android tag, then someone just needs to subscribe to that one tag. Or would you prefer they subscribe to dozens of Android-<feature> tag for every possible aspect of Android development? – thecoshman Jul 26 '13 at 14:55
  • I certainly think it should also be tagged android, as (again) I said in my answer. The aversion to multiple tags makes little sense to me, as long as they're used properly. – Joe Jul 26 '13 at 15:04
  • So you do actually think a question should have all three tags? – thecoshman Jul 26 '13 at 15:09
  • At least two (android and android-sdcard). sdcard I couldn't say if that would make sense or not as I don't know anything about SD Cards, but from Caleb's post above it sounds like not. (IE, would a non-android SD card developer find this post useful?) – Joe Jul 26 '13 at 15:13
  • To be honest I wish there were true sub-tags; that would make all of this discussion/argument/whatever moot. IE, high level tags like android and then tags that are never searchable by themselves because they have too many meanings. Maybe or maybe not relevant for sd-card but certainly helpful in a lot of other cases; graph for example has so many meanings it hurts... but it's useful in conjunction with other tags. – Joe Jul 26 '13 at 15:15
  • Actually, I disagree with this last point. If some has a question tagged as android-sdcard asking 'why is it so slow', they may feel rightfully tagged the question, "I'm using android, I'm using sd cards, so that tag makes sense" but they are effectively preventing someone who knows about sd-cards in general, but not android, pointing out "Oh, you are using such and such a brand, they are known for their very slow write speeds". – thecoshman Jul 26 '13 at 18:50

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