user63: As an long overdue conclusion to our experiment with series and franchise tags, I would like to suggest a new blanket policy on how use franchise tags and apply series continuity with series tags. 
There seems to be many users favoring the use of franchise tags, as they help keep series together and make them easier to look up. This is especially helpful for series with many different spin-offs or continuities (such as gundam).
In light of that, I would like to propose a new policy for the including franchise tags for all series with spin-off or continuities. Here are some suggested guideline on how to tag series of different continuities and determine if a franchise needs one.

Not all franchises need a series tag, but popular franchises with at least three major continuities (two if they have different continuities but share a very similar name like fullmetal-alchemist) and spin-offs benefit in having them as it helps keep things together and makes them more easily searchable and categorizable. We can consider a franchise to be popular if there are at least 10 questions about series within that franchise (e.g., gundam)
For an example, if you want to answer Gundam questions, but only want to only want to focus on question of the original UC universe, you can search the gundam-series and pick out specific UC series like gundam-unicorn. Splitting up the gundam tag allows users to better associate the tag with a specific series than the franchise as a whole.
Some series benefit is having metaverse tag, as there are works from specific groups that exist in a collective multiverse but are set in parallel universes. A fairly well-known example of this is the work of Nasu Kinoko of Type Moon, the writer behind the Fate/Stay Night and Tsukihime series. The works of the collective multiverse are referred to as the nasuverse, after him. 
Such series include not only the Fate and Tsukihime franchises, but also other Type Moon works such as Mahoutsukai no Yoru and Kara no Kyoukai. Many of these franchise share core concepts like the Root (Radix), Counter Force, Magecraft, and True Magic. Having such a metaverse tag makes asking more general questions on the worldbuilding concepts of the multiverses easier without needing to tie it down to a specific series or franchise
Series tags will be skewed in favor of their anime series, as users of this site tend to favor anime over manga. 
For an example, while the Dragonball manga includes the dragonball anime and dragonball-z anime, they are treated with seperate series tags
Questions specifically about the source material should use the syntax {{series-name}}-manga such as dragon-ball-manga for the Dragonball manga series and fullmetal-alchemist-manga for the Fullmetal Alchemist (Brotherhood) manga specifically. 
Questions on the novels and light novel source material specifically can use a similar syntax {{series-name}}-novel or {{series-name}}-vn ("visual novel" is abbreviated for brevity).
Example: robotics-note-vn for questions specifically about the Robotics; Note visual novel, perfect-insider-novel for question about the Perfect Insider (Subete wa F ni Naru)  
Split series based on universe/story continuity. Start with the name of the original series as the name for series tag. This way it's easier for users to decerns which series within a franchise with multiple continuities a question is referring to without needing to read the body.
For an example, all the Sailor Moon anime (R, S, Super S, Sailor Stars), with the exception of the Crystal reboot, in one continuous series. So the should be tagged as sailor-moon. sailor-moon-crystal should have it's own tag because it's of a seperate continuity. 
All tags should favor the English franchise/series name where possible (official-localized English names), but also have the original language name as a synonym. 
We are departing from the previous policy of "pick the most popular name based on web search results," because a majority of the time the original language names are popular, simply because they were known by these name before localizations (therefore skewed). Series with no localized names can get an exemption here, but once they do get localized, their name should be swapped and synonymized  
For series names try to abbreviate commonly recognizable words to make the titles shorter and keep them within the tag character limit. If a series name is too long try to abbreviate the title as best you can and add a synonym with as much as you can fit.  
For an example, "Fullmetal Alchemist: Brotherhood" can be abbreviated to fma-brotherhood and have the synonym "fullmetal-alchemist-bro." This is so if someone types in "fullmetal alchemist" when adding an tag, they will see both tags.

In simple terms what we are doing is:

Adding franchise tags to popular series with at least three different continuities or if two continuities in a series share a name. Only focus on the popular tags with at least 10 questions for now.
Examples: gundam-serieszeta-gundamgundam-08th-ms-teamvictory-gundam, fma-seriesfullmetal-alchemist-2003fma-brotherhood

You may add a metaverse tag (in place of a franchise tag) and include it in questions that asks about concepts that exists within a multiverse
Example: "What is the difference between the Mystic Eyes of Death Perception of Shiki Ryougi and Shiki Tohno?" nasuversekara-no-kyoukaitsukihime

Split series continuities based on whether they exist in the same universe. Use the name of the original series as the series tag. 
For an example, the 2003 Fullmetal Alchemist anime and the Brotherhood adaptation of the manga series have some very distinct differences in world, character, and story. The tags should be differentiated to avoid confusion.
Please use the official English language series names where possible. If none exist, use the the original language romanization, until it does get a localized name.

We are looking to normalize series tag titles to be in in English, because we are a primarily English language site.

Abbreviate the series names wherever possible and favor the anime series titles. As long is it is recognizable by fans then it should be fine. User your own discretion when adding a new title, if you are unsure ask for help on meta or chat.
For an example: Ouran Highschool Host Club can be abbreviated to ouran-hs-host-club. Fullmetal Alchemist: Brotherhood (being too long to fit unabbreviated) can become fma-brotherhood. With a fullmetal-alchemist-bro synonym so it shows up when someone types "fullmetal alchemist" when searching for a tag. 
Adding a tag synonym for abbreviated titles is optional, but highly recommended if you are altering the tag name drastically (like with Fullmetal Alchemist: Brotherhood) 
Only add a tag if there is a direct relevance to the question. Don't pad a question with unneeded tags.

Please take some time to review the proposal and suggest any changes or give general feedback. If acceptable, I'll look to implement these changes after the election.

user1908: This is an admirable effort, but ther are a few problems that I see.

Adding additional suffixes like -vn and whatnot is going to make our tag length problems even worse, leading to a need for more stupid abbreviated workarounds. 
This approach doesn't correctly represent the ontology of tags. "Higher-order" tags, like franchise and metaverse tags, should, in most cases, not really be tags, but rather be "properties" attached to series tags. Concretely, one will typically not ask a question about fma-series; rather, fma-series ought to be metadata on fullmetal-alchemist-2003 or whatever. Put alternatively, there should be an implication that any question tagged with fullmetal-alchemist-2003 is also about fma-series. Now, we obviously cannot correctly represent this ontology using Stack Exchange's current implementation of tags - but I don't know that this means we ought to turn to this alternate, hacky approach.
I know I harp on this, but it almost doesn't matter whether we pick the Japanese or English name if we (specifically you, moderators) just add the dag-blasted synonyms so that both of them show up when you type in a tag! 
That said, I do not think that a blanket policy of using English-language titles is necessarily desirable. For example, the English title for Hanasaku Iroha is "Blossoms for Tomorrow", but straight-up nobody calls it that. I can get on board with a concerted effort to move more things to English tags with Japanese synonyms, but there will be cases where we'll need to make exceptions to avoid stupid tag names.
It will be quite some time before enough questions use this new tagging approach for it to be useful for searching, favoriting, etc. If a shift to this approach is necessary and inevitable, then this doesn't matter, and we may as well get it over sooner than later. But I'm not convinced that it is either necessary or inevitable.


Consider this alternate proposal that 1.) mostly fixes the same core issue; 2.) avoids problems 2 and 5 from above; and 3.) gives us bonus features related to tag wildcards:
What if we abandoned franchise tags, and instead adopted consistent prefix schemes for tags that live in the same franchise? For example, instead of fma-series, we just have fma-brotherhood, fma-manga, fma-2003, fma-milos, and whatever else. For "metaverse" things like the Nasuverse, I think retaining separate tags for those is okay, though they should be used sparingly (e.g. when one has a question that necessarily draws on both Tsukihime and Fate or something). 
This, I believe, has the following advantages:

This is a more correct representation of the ontology of tags, though still not the one I would choose if I had the liberty to reimplement tagging from scratch.
We already have reasonably consistent prefixation for a number of these tags, meaning that the cutover to a fully consistent prefixation approach will not take nearly as long. Further, since this will involve tag renames rather than tag edits, it can be done non-disruptively using moderator tools, thus preventing gorillions of posts from being bumped to the front page as they are edited.
This is already the way a related problem is solved on Stack Overflow: versioned tags (python-2, python-2.7, python-3, python-3.4, etc). And as such, there is explicit support for this approach in search and when favoriting tags - use suffix wildcards like python-*. This is, in my opinion, the clearest advantage of a prefix-based scheme - we get to piggyback on all the stuff that has already been implemented for SO.


Slightly related note: about a year ago, I offhandedly proposed the idea of introducing structured metadata into tag wikis to better represent the ontologies we're dealing with. I haven't given this much more thought since then, but it could be a fruitful avenue to investigate. 

63: <p>As an long overdue conclusion to our <a href="https://anime.meta.stackexchange.com/questions/2719/a-certain-multivariate-experiment-testing-changes-to-series-tags-based-on-story">experiment</a> with series and franchise tags, I would like to suggest a new blanket policy on how use franchise tags and apply series continuity with series tags. </p>

<p>There seems to be many users favoring the use of franchise tags, as they help keep series together and make them easier to look up. This is especially helpful for series with many different spin-offs or continuities (such as <a href="https://anime.stackexchange.com/questions/tagged/gundam" class="post-tag" title="show questions tagged &#39;gundam&#39;" rel="tag">gundam</a>).</p>

<p>In light of that, I would like to propose a new policy for the including franchise tags for all series with spin-off or continuities. Here are some suggested guideline on how to tag series of different continuities and determine if a franchise needs one.</p>

<ul>
<li><p>Not all franchises need a series tag, but popular franchises with at least three major continuities (two if they have different continuities but share a very similar name like <a href="https://anime.stackexchange.com/questions/tagged/fullmetal-alchemist" class="post-tag" title="show questions tagged &#39;fullmetal-alchemist&#39;" rel="tag">fullmetal-alchemist</a>) and spin-offs benefit in having them as it helps keep things together and makes them more easily searchable and categorizable. We can consider a franchise to be popular if there are at least 10 questions about series within that franchise (e.g., <a href="https://anime.stackexchange.com/questions/tagged/gundam" class="post-tag" title="show questions tagged &#39;gundam&#39;" rel="tag">gundam</a>)</p>

<p>For an example, if you want to answer Gundam questions, but only want to only want to focus on question of the original UC universe, you can search the <a href="https://anime.stackexchange.com/questions/tagged/gundam-series" class="post-tag" title="show questions tagged &#39;gundam-series&#39;" rel="tag">gundam-series</a> and pick out specific UC series like <a href="https://anime.stackexchange.com/questions/tagged/gundam-unicorn" class="post-tag" title="show questions tagged &#39;gundam-unicorn&#39;" rel="tag">gundam-unicorn</a>. Splitting up the <a href="https://anime.stackexchange.com/questions/tagged/gundam" class="post-tag" title="show questions tagged &#39;gundam&#39;" rel="tag">gundam</a> tag allows users to better associate the tag with a specific series than the franchise as a whole.</p></li>
<li><p>Some series benefit is having metaverse tag, as there are works from specific groups that exist in a collective multiverse but are set in parallel universes. A fairly well-known example of this is the work of Nasu Kinoko of Type Moon, the writer behind the <em>Fate/Stay Night</em> and <em>Tsukihime</em> series. The works of the collective multiverse are referred to as the <a href="https://anime.stackexchange.com/questions/tagged/nasuverse" class="post-tag" title="show questions tagged &#39;nasuverse&#39;" rel="tag">nasuverse</a>, after him. </p></li>
<li><p>Such series include not only the <em>Fate</em> and <em>Tsukihime</em> franchises, but also other Type Moon works such as <em>Mahoutsukai no Yoru</em> and <em>Kara no Kyoukai.</em> Many of these franchise share core concepts like the Root (Radix), Counter Force, Magecraft, and True Magic. Having such a metaverse tag makes asking more general questions on the worldbuilding concepts of the multiverses easier without needing to tie it down to a specific series or franchise</p></li>
<li><p>Series tags will be skewed in favor of their anime series, as users of this site tend to favor anime over manga. </p>

<p>For an example, while the <em>Dragonball</em> manga includes the <a href="https://anime.stackexchange.com/questions/tagged/dragonball" class="post-tag" title="show questions tagged &#39;dragonball&#39;" rel="tag">dragonball</a> anime and <a href="https://anime.stackexchange.com/questions/tagged/dragonball-z" class="post-tag" title="show questions tagged &#39;dragonball-z&#39;" rel="tag">dragonball-z</a> anime, they are treated with seperate series tags</p></li>
<li>Questions specifically about the source material should use the syntax <code>{{series-name}}-manga</code> such as <a href="https://anime.stackexchange.com/questions/tagged/dragon-ball-manga" class="post-tag" title="show questions tagged &#39;dragon-ball-manga&#39;" rel="tag">dragon-ball-manga</a> for the <em>Dragonball</em> manga series and <a href="https://anime.stackexchange.com/questions/tagged/fullmetal-alchemist-manga" class="post-tag" title="show questions tagged &#39;fullmetal-alchemist-manga&#39;" rel="tag">fullmetal-alchemist-manga</a> for the <em>Fullmetal Alchemist (Brotherhood)</em> manga specifically. </li>
<li><p>Questions on the novels and light novel source material specifically can use a similar syntax <code>{{series-name}}-novel</code> or <code>{{series-name}}-vn</code> ("visual novel" is abbreviated for brevity).
Example: <a href="https://anime.stackexchange.com/questions/tagged/robotics-note-vn" class="post-tag" title="show questions tagged &#39;robotics-note-vn&#39;" rel="tag">robotics-note-vn</a> for questions specifically about the <em>Robotics; Note</em> visual novel, <a href="https://anime.stackexchange.com/questions/tagged/perfect-insider-novel" class="post-tag" title="show questions tagged &#39;perfect-insider-novel&#39;" rel="tag">perfect-insider-novel</a> for question about the <em>Perfect Insider</em> (<em>Subete wa F ni Naru</em>)  </p></li>
<li><p>Split series based on universe/story continuity. Start with the name of the original series as the name for series tag. This way it's easier for users to decerns which series within a franchise with multiple continuities a question is referring to without needing to read the body.</p>

<p>For an example, all the <em>Sailor Moon</em> anime (<em>R, S, Super S, Sailor Stars</em>), with the exception of the <em>Crystal</em> reboot, in one continuous series. So the should be tagged as <a href="https://anime.stackexchange.com/questions/tagged/sailor-moon" class="post-tag" title="show questions tagged &#39;sailor-moon&#39;" rel="tag">sailor-moon</a>. <a href="https://anime.stackexchange.com/questions/tagged/sailor-moon-crystal" class="post-tag" title="show questions tagged &#39;sailor-moon-crystal&#39;" rel="tag">sailor-moon-crystal</a> should have it's own tag because it's of a seperate continuity. </p></li>
<li><p>All tags should favor the English franchise/series name where possible (official-localized English names), but also have the original language name as a synonym. </p></li>
<li><p>We are departing from the previous policy of "pick the most popular name based on web search results," because a majority of the time the original language names are popular, simply because they were known by these name before localizations (therefore skewed). Series with no localized names can get an exemption here, but once they do get localized, their name should be swapped and synonymized  </p></li>
<li><p>For series names try to abbreviate commonly recognizable words to make the titles shorter and keep them within the tag character limit. If a series name is too long try to abbreviate the title as best you can and add a synonym with as much as you can fit.  </p>

<p>For an example, "<em>Fullmetal Alchemist: Brotherhood</em>" can be abbreviated to <a href="https://anime.stackexchange.com/questions/tagged/fma-brotherhood" class="post-tag" title="show questions tagged &#39;fma-brotherhood&#39;" rel="tag">fma-brotherhood</a> and have the synonym "fullmetal-alchemist-bro." This is so if someone types in "fullmetal alchemist" when adding an tag, they will see both tags.</p></li>
</ul>

<p>In simple terms what we are doing is:</p>

<ul>
<li><p><strong>Adding franchise tags to popular series</strong> with at least three different continuities or if two continuities in a series share a name. <strong>Only focus on the popular tags with at least 10 questions for now.</strong></p>

<p>Examples: <a href="https://anime.stackexchange.com/questions/tagged/gundam-series" class="post-tag" title="show questions tagged &#39;gundam-series&#39;" rel="tag">gundam-series</a><a href="https://anime.stackexchange.com/questions/tagged/zeta-gundam" class="post-tag" title="show questions tagged &#39;zeta-gundam&#39;" rel="tag">zeta-gundam</a><a href="https://anime.stackexchange.com/questions/tagged/gundam-08th-ms-team" class="post-tag" title="show questions tagged &#39;gundam-08th-ms-team&#39;" rel="tag">gundam-08th-ms-team</a><a href="https://anime.stackexchange.com/questions/tagged/victory-gundam" class="post-tag" title="show questions tagged &#39;victory-gundam&#39;" rel="tag">victory-gundam</a>, <a href="https://anime.stackexchange.com/questions/tagged/fma-series" class="post-tag" title="show questions tagged &#39;fma-series&#39;" rel="tag">fma-series</a><a href="https://anime.stackexchange.com/questions/tagged/fullmetal-alchemist-2003" class="post-tag" title="show questions tagged &#39;fullmetal-alchemist-2003&#39;" rel="tag">fullmetal-alchemist-2003</a><a href="https://anime.stackexchange.com/questions/tagged/fma-brotherhood" class="post-tag" title="show questions tagged &#39;fma-brotherhood&#39;" rel="tag">fma-brotherhood</a></p>

<ul>
<li><p><strong>You may add a metaverse tag</strong> (in place of a franchise tag) and include it in questions that asks about concepts that exists within a multiverse</p>

<p>Example: <em>"What is the difference between the Mystic Eyes of Death Perception of Shiki Ryougi and Shiki Tohno?"</em> <a href="https://anime.stackexchange.com/questions/tagged/nasuverse" class="post-tag" title="show questions tagged &#39;nasuverse&#39;" rel="tag">nasuverse</a><a href="https://anime.stackexchange.com/questions/tagged/kara-no-kyoukai" class="post-tag" title="show questions tagged &#39;kara-no-kyoukai&#39;" rel="tag">kara-no-kyoukai</a><a href="https://anime.stackexchange.com/questions/tagged/tsukihime" class="post-tag" title="show questions tagged &#39;tsukihime&#39;" rel="tag">tsukihime</a></p></li>
</ul></li>
<li><p><strong>Split series continuities based on whether they exist in the same universe</strong>. Use the name of the original series as the series tag. </p>

<p>For an example, the 2003 <em>Fullmetal Alchemist</em> anime and the <em>Brotherhood</em> adaptation of the manga series have some very distinct differences in world, character, and story. The tags should be differentiated to avoid confusion.</p></li>
<li><p><strong>Please use the official English language series names where possible.</strong> If none exist, use the the original language romanization, until it does get a localized name.</p>

<ul>
<li>We are looking to normalize series tag titles to be in in English, because we are a primarily English language site.</li>
</ul></li>
<li><p><strong>Abbreviate the series names wherever possible and favor the anime series titles.</strong> As long is it is recognizable by fans then it should be fine. User your own discretion when adding a new title, if you are unsure ask for help on meta or chat.</p>

<p>For an example: <em>Ouran Highschool Host Club</em> can be abbreviated to <a href="https://anime.stackexchange.com/questions/tagged/ouran-hs-host-club" class="post-tag" title="show questions tagged &#39;ouran-hs-host-club&#39;" rel="tag">ouran-hs-host-club</a>. <em>Fullmetal Alchemist: Brotherhood</em> (being too long to fit unabbreviated) can become <a href="https://anime.stackexchange.com/questions/tagged/fma-brotherhood" class="post-tag" title="show questions tagged &#39;fma-brotherhood&#39;" rel="tag">fma-brotherhood</a>. With a <a href="https://anime.stackexchange.com/questions/tagged/fullmetal-alchemist-bro" class="post-tag" title="show questions tagged &#39;fullmetal-alchemist-bro&#39;" rel="tag">fullmetal-alchemist-bro</a> synonym so it shows up when someone types "fullmetal alchemist" when searching for a tag. </p>

<p>Adding a tag synonym for abbreviated titles is optional, but highly recommended if you are altering the tag name drastically (like with <em>Fullmetal Alchemist: Brotherhood</em>) </p></li>
<li><p><strong>Only add a tag if there is a direct relevance to the question.</strong> Don't pad a question with unneeded tags.</p></li>
</ul>

<p>Please take some time to review the proposal and suggest any changes or give general feedback. If acceptable, I'll look to implement these changes after the election.</p>
 1908: <p>This is an admirable effort, but ther are a few problems that I see.</p>

<ol>
<li>Adding additional suffixes like <code>-vn</code> and whatnot is going to make our <a href="https://meta.stackexchange.com/q/209248/">tag length problems</a> even worse, leading to a need for more stupid abbreviated workarounds. </li>
<li>This approach doesn't correctly represent the ontology of tags. "Higher-order" tags, like franchise and metaverse tags, should, in most cases, not really be tags, but rather be "properties" attached to series tags. Concretely, one will typically not ask a question about <code>fma-series</code>; rather, <code>fma-series</code> ought to be metadata on <code>fullmetal-alchemist-2003</code> or whatever. Put alternatively, there should be an <em>implication</em> that any question tagged with <code>fullmetal-alchemist-2003</code> is <em>also</em> about <code>fma-series</code>. Now, we obviously cannot correctly represent this ontology using Stack Exchange's current implementation of tags - but I don't know that this means we ought to turn to this alternate, hacky approach.</li>
<li>I know I harp on this, but <strong>it almost doesn't matter</strong> whether we pick the Japanese or English name if we (specifically you, moderators) just add the dag-blasted synonyms so that both of them show up when you type in a tag! </li>
<li>That said, I do not think that a blanket policy of using English-language titles is necessarily desirable. For example, the English title for <em>Hanasaku Iroha</em> is "Blossoms for Tomorrow", but straight-up nobody calls it that. I can get on board with a concerted effort to move <em>more</em> things to English tags with Japanese synonyms, but there will be cases where we'll need to make exceptions to avoid stupid tag names.</li>
<li>It will be quite some time before enough questions use this new tagging approach for it to be useful for searching, favoriting, etc. If a shift to this approach is necessary and inevitable, then this doesn't matter, and we may as well get it over sooner than later. But I'm not convinced that it <em>is</em> either necessary or inevitable.</li>
</ol>

<hr>

<p>Consider this alternate proposal that 1.) mostly fixes the same core issue; 2.) avoids problems 2 and 5 from above; and 3.) gives us bonus features related to tag wildcards:</p>

<p>What if we abandoned franchise tags, and instead adopted consistent <em>prefix</em> schemes for tags that live in the same franchise? For example, instead of <code>fma-series</code>, we just have <code>fma-brotherhood</code>, <code>fma-manga</code>, <code>fma-2003</code>, <code>fma-milos</code>, and whatever else. For "metaverse" things like the Nasuverse, I think retaining separate tags for those is okay, though they should be used sparingly (e.g. when one has a question that necessarily draws on both <em>Tsukihime</em> and <em>Fate</em> or something). </p>

<p>This, I believe, has the following advantages:</p>

<ul>
<li>This is a more correct representation of the ontology of tags, though still not the one I would choose if I had the liberty to reimplement tagging from scratch.</li>
<li>We already have reasonably consistent prefixation for a number of these tags, meaning that the cutover to a fully consistent prefixation approach will not take nearly as long. Further, since this will involve tag <em>renames</em> rather than tag <em>edits</em>, it can be done non-disruptively using moderator tools, thus preventing gorillions of posts from being bumped to the front page as they are edited.</li>
<li>This is already the way a related problem is solved on Stack Overflow: <em>versioned</em> tags (<code>python-2</code>, <code>python-2.7</code>, <code>python-3</code>, <code>python-3.4</code>, etc). And as such, there is explicit support for this approach in search and when favoriting tags - use suffix wildcards like <code>python-*</code>. This is, in my opinion, the clearest advantage of a prefix-based scheme - we get to piggyback on all the stuff that has already been implemented for SO.</li>
</ul>

<hr>

<p>Slightly related note: about a year ago, <a href="https://anime.meta.stackexchange.com/questions/2427/should-we-allow-genre-meta-tags#comment4647_2432">I offhandedly proposed the idea of introducing structured metadata into tag wikis</a> to better represent the ontologies we're dealing with. I haven't given this much more thought since then, but it could be a fruitful avenue to investigate. </p>
