This topic is dedicated to the disambiguation and standardisation of the various tags that describe lifting legs and feet. But first, some perspective on why this is needed.
"One leg lifted up and away from the other leg so that they are spread wide apart: one in the air, the other resting."
The leg_lift wiki currently describes the kind of poses seen in post #3118262 and post #2854945. However, its non-intuitive/ambiguous name has led to it being used in place of legs_up, leg_up, knees_up, knee_up and feet_up, just to name a few.
While researching this, I discovered that all of these legs/feet tags with the "_up" suffix are as commonly misused as the others, with the only wiki standardisation being between legs_up and leg_up (and even that isn't 100%). I propose concretely defining and standardising all of these tags, and at the very least tag gardening the most recent posts featuring them so users who don't use wikis see the recent examples as correct rather than a mix of correct/incorrect.
legs_up
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The legs_up wiki currently reads:
Any position in which both legs are thrust upward into the air, rather than resting on a surface.
To me at least, this wording gives the impression that legs_up only applies when the legs are outstretched as if standing on tiptoes. The "rather than resting on a surface" part also seems redundant, given that something cannot rest on a surface and be in the air at the same time. I propose changing the legs_up wiki to this:
Any position in which both legs are lifted into the air.
If the character's knees are on the ground with both feet lifted into the air, use feet up instead.
Examples of eligible posts would include post #3000327, post #3393634, post #3280384
leg_up
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The leg_up wiki currently reads:
Any position where a single leg is lifted into the air, rather than resting on a surface.
I wouldn't change much here - simply adding a disambiguation note and removing the mention of being on a surface like what I proposed for legs_up seems enough. I propose changing the leg_up wiki to this:
Any position where a single leg is lifted into the air.
If one or both of the character's knees are on the ground with a single foot connected to a grounded knee lifted into the air, use foot up instead.
Examples of eligible posts would include post #3408260, post #3378968, post #2561766 and post #3404330.
leg_lift
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The leg_lift wiki currently reads:
One leg lifted up and away from the other leg so that they are spread wide apart: one in the air, the other resting.
As I highlighted earlier, this tag is probably the most misused of all of those listed here. The initial wiki version mentions that the character must be in a lying pose, but the original author quickly changed it to remove this. Perhaps they felt it was simply common sense and therefore didn't need to be a part of the wiki, or they realised that some standing posts should fit the criteria. Whatever the reason, its name is too similar to the other *_up tags for a few disambiguation notes in a wiki to stop it from being misused. I propose completely renaming the tag to raised_leg and creating a new wiki for it:
One leg lifted up and away from the other leg so that they are spread wide apart: one in the air, the other resting or supporting the body.
For a leg lifted into the air but not spread apart from the other, see leg up.
For a foot lifted into the air while the knee remains on the ground, see foot up.
The definition that this tag has gone by all these years actually means that every leg_lift (or raised_leg) post that is tagged correctly should also be tagged leg_up, so once this tag is finally cleaned up it should also probably imply leg_up.
Examples of eligible posts would include post #2436252, post #3118262 and post #2608496.
knees_up
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The knees_up wiki currently reads:
When one's knees are in the air as a result of sitting or lying with bent legs.
knees_up could go one of two ways due to posts such as post #3250209 - either we make a flat rule that if the feet are off of the ground it counts as legs_up instead, or we say that if the feet are off the ground but still lower than the knees then it can count as both knees_up and legs_up. Personally, I believe the latter is the better choice. I propose changing the knees_up wiki to this:
When one's knees are in the air as a result of sitting or lying with bent legs.
If the feet are also lifted into the air but remain lower than the knees, then also add legs up. If the feet are lifted to the same level or higher than the knees, use legs up and not knees_up.
Examples of eligible posts would include post #3406489, post #2935871 and post #2724883.
knee_up
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The knee_up wiki currently reads:
A single knee is raised into the air. For kneeling on only one knee, use one knee.
Mostly the same points as knees_up, but for only one knee at a time. The disambiguation note here seems to have done a good job of keeping one_knee posts such as post #3384106 from polluting knee_up, so we should keep it. I propose changing the knee_up wiki to this:
When a single knee is in the air as a result of sitting or lying with a bent leg.
If the foot is also lifted into the air but remains lower than the knee, then also add leg up. If the foot is lifted to the same level or higher than the knee, use leg up and not knee_up.
Examples of eligible posts would include post #3407329, post #3377987 and post #3371041.
feet_up
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The feet_up wiki currently reads:
When a character is raising their feet off the ground.
If you just see one or both legs being raised but can't see the feet, use legs up instead.
This is somewhat confusing to read and also conflicts with the current wiki for legs_up, leading to users adding feet_up to posts when they are actually trying to tag what legs_up is for. In addition, I think it's a good idea to use feet_up and foot_up only for posts where a character's knees are on the ground - while it is possible to lift up the foot and not the whole leg while standing, using feet_up and foot_up for standing poses as well as on_stomach poses is a part of why they're such a mess right now. There's not really any other way to word it when talking about on_stomach poses, and if used on standing poses they'd quickly start to be mistakenly used instead of leg_up. Keeping these things in mind, I propose changing the feet_up wiki to this:
When a character's knees are on the ground with both feet lifted into the air.
If the character's knees are not on the ground and they have both legs lifted into the air, use legs up instead.
Examples of eligible posts would include post #3407478, post #3336870 and post #2313651.
foot_up
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The foot_up wiki currently reads:
One foot being braced on a solid surface above another.
For one foot being lifted up in the air, use leg up instead. For the toes being lifted with the foot on the ground, use toes up.
This is both the newest and least standardised tag, as it describes a pose very different to the other *_up tags already in use. That being said, I feel that the foot position it currently describes is still worthy of its own tag - my suggestion is to change the tag for this pose from foot_up to elevated_foot, which I believe is sufficiently different to avoid a majority of the mistagging it currently exhibits. After that, I propose changing the foot_up wiki to this:
When one or both of a character's knees are on the ground, with a single foot connected to a grounded knee lifted into the air.
If the character is not on their knee(s) and has a single leg lifted into the air, use leg up instead.
Examples of eligible posts would include post #3294121, post #3316947 and post #3290991.
heel_up
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The heel_up wiki currently does not exist:
I suggested this tag on the Danbooru Discord server but utterly failed to remember to create a wiki for it, or ask on the forums whether other users thought it would be a good idea. It describes when a character has a single heel up, resting most of their weight on one side of the body and propping the other side's foot up with their toes. I was surprised when I found out this wasn't being tagged, as it is a fairly common foot pose. We also needn't consider when both heels are up, because tiptoes already covers that. I propose creating the heel_up wiki as follows:
When a character has a single heel raised, with the only part of the foot touching the ground being the toes.
If both heels are raised off of the ground, use tiptoes instead.
Examples of eligible posts would include post #3274950, post #3339121 and post #3374108.
toes_up
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The toes_up wiki currently reads:
For when the ball of the foot is on the ground with the toes raised.
For the whole foot up in the air, use leg up.
This was created at around the same time as heel_up. It would serve as something of a counterpart to heel_up and describes when the ball of the foot is the only part supporting the leg/body it is attached to. Due to the nature of the wording of "toes", I think it's best if we make toes_up count when either one or both feet are supported by their balls.
...what? What's so funny?
In any case, I propose changing the toes_up wiki to this:
For when the ball of the foot is on the ground with the toes raised. Use this if it applies to one foot or both feet.
If the whole foot is in the air, use leg up. If both whole feet are in the air, use legs up.
Examples of eligible posts would include post #3007601, post #3346725 and post #3407394.
For formalities' sake I'm mentioning top-down_bottom-up too but I think we can all agree that there is almost nothing that a user could confuse this with, except maybe a shirt_pull + skirt_lift combo - and even then a single cursory search should be enough to show what the tag is really for.
This big a project will require a large effort, but it's best if we grab it by the horns now rather than let it fester even longer until it's twice as awful a few years down the track. Your thoughts, input and suggestions are all very welcome, as is any effort you decide to put into tag gardening once everything is ready to start moving.
Gelbooru rulez!!!