# I don't understand why - by design - “ion-thruster” tag remains hidden when I start typing “ion…”

I wanted to see if there was an ion-thruster or ion-propulsion tag when I was writing this question. When I started typing ion some tags appeared, but nothing with the word ion in it instead, other tags that contained that sequence of three letters appeared. However, when I stated typing thr, then "ion-thruster" appeared.

Is this unexpected behavior? Shouldn't typing the first three letters ion show me (at least) things that begin with those three letters?

I've used the tag bug here, because I found this behavior to be unexpected.

• It's also strange that mission design appeared on the right... There's something unusual about that... – PearsonArtPhoto Jun 12 '16 at 13:21
• @PearsonArtPhoto "instead, other tags that contained that sequence of three letters appeared." - mission-design, communication, colonization, radiation – uhoh Jun 12 '16 at 13:29
• I had to type "ion-pr" before it came up as an option. Weird. – Jerard Puckett Jun 14 '16 at 15:22
• Also, [ion-engine] is not yet a synonym for [ion-propulsion], and it's beyond my capacity to do more than suggest it here. – Jerard Puckett Jun 14 '16 at 15:26
• And also [ion-drive] and [ion-thruster]. – Jerard Puckett Jun 14 '16 at 15:29
• @JerardPuckett good to know! I think the "status-bydesign" tag on my question is - in this case - not appropriate. This is an actual bug - an unintended behavior. I am uncomfortable with it being there - it seems to say "it's supposed to do that!" – uhoh Jun 14 '16 at 15:29
• @JerardPuckett Since the three letter word ion is a pretty potent word, it shouldn't be excluded and hidden "by design." It should pop up immediately in this case. I suspect this would have to be a feature request, if it continues to be tagged in red as not a bug. – uhoh Jun 14 '16 at 15:32
• Bumping this because the problem still exists, and I too am confused why it is "by design". I understand that it is working according to how the tag search algorithm is supposed to work, but it is not working in such a way that users can easily find the tags they need. – called2voyage Aug 19 at 14:26

Hyphens are excluded from tag autocomplete. appears as you type ion-t or iont -- hyphens are ignored both ways.

Also, tag autocomplete is a full text substring match, not a prefix search, by design.

• Can you explain that in less-technical terms? This is space exploration stackexchange, not stackoverflow. I'm not a programmer. Thanks! I'd like to suggest that this behavior is not good because it prevented me from finding the tag by typing the first three letters of the tag - I would have had to guess that there is a hyphen. More experienced people might know about the hyphen replacing the space, but I didn't, and surely other's won't either. – uhoh Jun 13 '16 at 10:03
• @uhoh Does this help? "full text substring match": the text you specify is looked for anywhere in the tag name; "prefix search": the text you specify is looked for only at the beginning of the tag name. – Sklivvz Jun 13 '16 at 10:13
• Well it's the proximal cause - like "Why was the light red?" "Because of the band gap." Is there a reason why it was designed to not show it in this case, why tags with the word ion are hidden while tags without the word ion are shown, giving the false impression that there are no ion related tags? This behavior is by design? Really? – uhoh Jun 13 '16 at 12:11
• It's not designed not to show, in fact it shows when you search in the tag page: i.stack.imgur.com/0ukqK.png. For space reasons we can't possibly show all matches all the time. "ion" is very common and matches many tags. We pick the tags which are most used first by design. – Sklivvz Jun 13 '16 at 14:15
• Ah! most used. OK I understand now. Thank you for taking the time to get back to me and clarify - I appreciate it! Some day, a short string separated by a hyphen might be flagged by an AI algorithm as a higher priority match than those where it is embedded in the middle or end of a word. The presence of the hyphen, combined with the rarity, should actually boost the score of the match and pop it tot the top of the list. But that's someday :) – uhoh Jun 13 '16 at 14:28
• @Sklivvz Would it be possible to put a little more weight on the tags that start with the string entered? It would seem like this particular case is undesirable. – called2voyage Jun 13 '16 at 15:15
• Actually if you look at my screen shots, there are only four tags shown in each case (well, maybe 4.5 for the first one) so I'm curious how the most used filter is actually implemented here. Is it a statistical analysis? Does it detect a bimodal distribution and put the cut in the middle, or just say anything under N uses is dropped? - there IS plenty of room for more tags to be displayed in that box, and yet it hides the one I need to see - by design! – uhoh Jun 14 '16 at 15:35
• @uhoh: It grabs the six most likely tags, then trims any you already put in the question, but does not free up their space. This is a consistent design, but a consistently surprising one (to me, at least). – Nathan Tuggy Jul 13 '16 at 17:39
• @NathanTuggy Oh, thanks for that! I'm (very slowly) making a little list of cases where a word-aware algorithm might help. If the algorithm recognized that the string 'ion' appeared as a complete word in a tag, or the beginning of a word, it should pop to the top of the list. Here word just means a string in a tag either by itself, or delimited by a hyphen. Thus if 'ion-drive' or 'ionization' tags exist, they should receive a higher weight, or simply pop to the top of the list maybe. But that would probably need some testing on real tag populations first. – uhoh Jul 13 '16 at 23:43
• @NathanTuggy so if I'm unhappy with anything, it's that this behavior was quickly labeled "by design" which allows a single person to effectively silence the discussion. Effective - and therefore busy - people will move on as soon as they see that big red stamp. I think this behavior is NOT by design. I am pretty sure it is a bug as I say here. I'd like the "by design" tag to be removed - at least for a while, so the bug-like nature could receive consideration. – uhoh Jul 13 '16 at 23:48
• @NathanTuggy sorry to post three comments in a row - is consistent behavior sufficient to be considered "by design", or does it require - in some way - a programmer to actually step up and say "yes - that is exactly the behavior I was trying for -I designed it to behave in just that way"? – uhoh Jul 14 '16 at 1:25
• @uhoh: It requires an SE employee (or sometimes a mod who is sufficiently in tune with SE internals) to say that the programmer intended it. (I'm digging up a link re something else you already mentioned, btw.) – Nathan Tuggy Jul 14 '16 at 1:28
• @uhoh You should probably add your voice to meta.stackexchange.com/questions/273448/… which focuses a bit more on this basic issue of <6 tags returned. – Nathan Tuggy Jul 14 '16 at 1:42
• @called2voyage thanks for the [bump](). In 2016 I was too timid to pursue this further, but I've run into the no ion-drive option a few times more since then. Comments here may be helpful towards coming up with ideas for a better design. – uhoh Aug 19 at 23:56