<p>A great example is in Japanese names, which are natively written surname first. <i>character:ayanami rei</i> and <i>character:rei ayanami</i> have the same meaning, but different users will use one, or the other, or even both.</p>
<p>Other examples are tiny syntactic changes, common misspellings, and unique acronyms:
<ul>
<li><i>smiling</i> and <i>smile</i></li>
<li><i>staring at camera</i> and <i>looking at viewer</i></li>
<p>A particular repository may have a preferred standard, but it is not easy to guarantee that all the users will know exactly which tag to upload or search for.</p>
<p>Without continual intervention by janitors or other experienced users to make sure y⊇x (i.e. making the yellow circle entirely overlap the blue by manually giving y to everything with x), searches can only return x (blue circle) or y (yellow circle) or x∩y (the lens-shaped overlap). What we really want is x∪y (both circles).</p>
<p>This relationship is transitive, which means as well as saying A->B, you can also say B->C, which implies A->C and B->C.</p>
<p><imgsrc="tag_siblings_usa.png"/></p>
<p>You can also have an A->C and B->C that does not include A->B.</p>
<p><imgsrc="tag_siblings_what_is_a_man.png"/></p>
<p>The outcome of these two arrangements is the same (everything ends up as C), but the underlying semantics are a little different if you ever want to edit them.</p>
<p>Many complicated arrangements are possible:</p>
<p><imgsrc="tag_siblings_yo_dawg.png"/></p>
<p>Note that if you say A->B, you cannot say A->C; the left-hand side can only go to one. The right-hand side can receive many. The client will stop you from constructing loops.</p>
<p>Please note that siblings' autocomplete counts may be slightly inaccurate, as unioning the <i>count</i> is difficult to quickly estimate.</p>
<p>The client will not collapse siblings anywhere you 'write' tags, such as the manage tags dialog. You will be able to add or remove A as normal, but it will be written in some form of "A (B)" to let you know that, ultimately, the tag will end up displaying in the main gui as B:</p>
<p>Although the client may present A as B, it will secretly remember A! You can remove the association A->B, and everything will return to how it was. <b>No information is lost at any point.</b></p>
<p>Whenever you add or remove a tag sibling pair to a tag repository, you will have to supply a reason (like when you petition a tag). A janitor will review this petition, and will approve or deny it. If it is approved, all users who synchronise with that tag repository will gain that sibling pair. If it is denied, only you will see it.</p>
