Estimating the prediction variance in kernel ridge regression

Question: I'm trying to estimate the variance of predictions for a kernel ridge regression model.
The model is simply kernel ridge regression:
$$\hat{y} = K(K+\lambda I)^{-1}y = A y$$
$K$ is the $n \times n$ kernel matrix (any arbitrary kernel, but I would like to use the linear kernel and RBF kernel especially), $\lambda > 0$ is the regularization parameter, and $y$ are the regression targets and $\hat{y}$ are the predictions. $A$ is comparable to the hat matrix $H$ in regular linear regression, except for the fact that it's not idempotent or symmetric.
I guess using this model my assumptions are that:
$$ y_i = f(x_i) + \epsilon$$
$$\epsilon \sim N(0,\sigma^2)$$
And $x_i$ is the feature vector of object $i$ in kernel space, and $f$ is a linear function (I think?).
To find the variance of the predictions we get that:
$$\text{Cov}(y) = A A^T \sigma^{*2}$$
Here, $\sigma^{*2}$ is the error variance of the non-regularized model.
I now want to estimate $\sigma^*$. In regular linear regression we can estimate $\sigma^2$ using the formula:
$$\sigma^2 \approx S_E^2 = \frac{e^T e }{n-df}$$
Where $e$ is the vector of residuals and $df$ is the degrees of freedom of the model. However, I'm not entirely sure if I can use the formula for $S_E^2$, and I'm not sure how to derive it for the kernelised case. $df$ is:
$$df = \text{trace}(A)$$
However, if we use no regularization, I find that:
$$df = \text{trace}(KK^{-1}) = \text{trace}(I) = n$$
Therefore I cannot calculate $S_E^2$, since I divide by zero. However, notice that if you don't use any regularization, we get that:
$$e = \hat{y} - y = Ay - y = 0$$
Since $A = I$ in the case of no regularization. So actually you divide zero by zero, so I thought maybe taking the limit of $\lambda \to 0$ we can might still be able to use the formula for $S_E$. However, my intuition tells me that $e^T e$ will go faster to zero, since it is quadratic in $A$, while the numerator is probably linear (?) in $A$ (the trace). I guess you could make this more exact by using the eigenvalue decomposition of $K$.
I performed a small experiment in Matlab where I compute $S_E^2$ for values of $\lambda$ going to zero and I found that $S_E^2$ goes to zero very fast for small values of $\lambda$, so it appears to be the case that $\sigma = 0$.
However to conclude that $\sigma = 0$ and thus that the variance of $\hat{y}$ is equal to zero for the kernel ridge regression model seems implausible to me. I guess a different approach would be to use bootstrapping to compute the variances of $\hat{y}$, however it feels like there should be some better way to attack this problem (I would like to compute it analytically if possible). In any case, with a linear kernel I don't have this problem (since in this case $df \neq 0$ and $e \neq 0$), but I would like to use the RBF kernel as well.
Answer: For anyone interested, this paper helped me a lot further:
Estimating Predictive Variances with Kernel Ridge Regression by G. C. Cawley
, N. L. C. Talbot and O. Chapelle
Note that this paper explains how to do it for heteroscedastic noise, however you can also use it for homogeous noise as follows.
The first method, KRR + LOO:

Train the KRR model on the data
For each sample, compute the LOO error
To estimate the $\sigma^2$ compute the sum of squared residuals that were found in step 2

A more detailed method is KRR + LOO + KRR.

Train the KRR model on the data
For each sample, compute the LOO error
Train a KRR model on the squared residuals that were found in step 2
The predictions of the second model are the prediction variances, however now we have to regularize two models, but we do get heteroscedastic variances. I guess I could also take the mean prediction of the second KRR model to find the homogeous noise term $\sigma^2$, but I'm unsure if this is useful or better than the above method.

Finally, they propose a new model, that will directly take heteroscedastic noise into account. This way, the model can be regularized more in noisy regions in feature space, and thus this model is expected to perform better.
In the end what I am really interested in is to estimate the probability distribution of the prediction on unseen / new data. The methods that I am now considering are:

Performing the KRR + LOO method to estimate $\sigma^2$. Now I can estimate the variance of new data using:
$$ \hat{y_{new}} = K_{x_{new},X_{trainset}} (K_{X_{trainset},X_{trainset}} + \lambda I)^{-1} y_{train} = P y_{train}$$
Using the identity:
$$ Cov(Xa) = X^T Cov(a) X$$
I obtain:
$$ Cov(\hat{y_{new}}) = P_{train}^T P_{train} \sigma^2 $$
I use the prediction on unseen data of the regular KRR model as the mean for the distribution.
Performing KRR + LOO + KRR. I have two choices, I either estimate $\sigma^2$ by averaging the outputs of the second KRR model and use the above formula, or I directly use the prediction of the second KRR model on new data to estimate the prediction variance of a new point.
I use the prediction on unseen data of the regular KRR model as the mean for the distribution.
I use their new model to estimate the mean and variance at unseen data.
I use bootstrapping to train multiple models, and I compute the variance of their predictions on the traindata. This way I can compute $\sigma^2$. Then I use the same formula as in 1. I use the prediction on unseen data of the regular KRR model as the mean for the distribution.
I use bootstrapping to train multiple models, and I compute their predictions on my new data. I compute the variance of those predictions, to compute the prediction variance of each point.
I use the prediction on unseen data of the regular KRR model as the mean for the distribution.

What I am a bit confused about is the actual distribution of the prediction on data at a new point. Is this distribution actually a Gaussian / normally distributed?
Comment: Was this intended as an answer to your question, or a
new question? Please only use the "Your Answer" field to provide
answers to the original question. If you have a new question, click the gray `ASK QUESTION` at the top of the page & ask it there, then we can help you properly.


Is it breaking and entering to open an unlocked for-sale car at a closed car dealership?

Question: Some people like to shop for cars when car dealerships are closed to avoid the salesmen. While looking at cars for sale at a closed car dealership, is it breaking and entering to open the door of an unlocked car?
Answer: Florida law states that

810.02 Burglary.— (1)(a) For offenses committed on or before July 1, 2001, "burglary" means entering or remaining in a dwelling, a
  structure, or a conveyance with the intent to commit an offense
  therein, unless the premises are at the time open to the public or the
  defendant is licensed or invited to enter or remain.
  Florida Statutes & Constitution : Online Sunshine: 810.02 Burglary

There are two relevant points here. (In this context, a "conveyance" means an automobile).
One is that Florida law states that there must be intent to commit a crime when entering a vehicle. This would be the case where someone steals parts (or the whole car) from a dealership; a crime was committed. But it would be difficult to show that people browsing through cars have intent to commit a crime, because the car dealership is in the business of selling cars, people have to get into a car to evaluate it, and during business hours, people enter the cars without salesmen.
Florida laws doesn't clearly differentiate between locked and unlocked doors when entering a conveyance or building; but obviously there would damage to a car by forcing entry by braking a window or crowbarring the door, and that is a separate crime covered under the same chapter of law.
The second point is the qualifier that "...unless the premises are at the time open to the public or the defendant is licensed or invited."
One could argue that the dealership - by not securing the car lot with a fence or signage that states "no trespassing" during certain hours - is still open to the public, even though the dealership is obviously private property. And by remaining accessible after hours, the public has been invited onto the property.
If you looked, you may see boilerplate signage at the dealership that states it is open after hours, though they are not responsible for injuries, etc.
Answer: Not necessarily "breaking and entering", and clearly not "burglary", but almost certainly trespass, unless you can prove you were "invited" to enter the vehicle.

810.08 Trespass in structure or conveyance.— (1) Whoever, without being authorized, licensed, or invited, willfully enters or remains in
  any structure or conveyance, or, having been authorized, licensed, or
  invited, is warned by the owner or lessee of the premises, or by a
  person authorized by the owner or lessee, to depart and refuses to do
  so, commits the offense of trespass in a structure or conveyance.Florida Statutes 2017
Comment: I cover this in the second to the last paragraph of my answer.
Comment: Being "invited onto the property" is certainly distinct from being invited to enter the vehicles that happen to be parked upon that property.


How to level up low flower beds?

Question: I am a beginner at gardening.
My flower beds are lower than the lawn; I want to build beds to the level of the lawn.
My late husband did all gardening, so I am at a loss of what to do. Do I use compost or soil or both?
Answer: As a beginner and a new learner, may I  suggest bringing a sample of the soil to your local garden center and ask them what they recommend?  Your local Agricultural Extension office may offer those services for free or a small charge. They may be able to test it and tell you if you need any particular amendments and how it stands up as a healthy soil.
Absent that, it's hard to go wrong with a good compost mix. Organic matter like compost a great amendment to just about any soil, but the cost of adding it in bulk can sometimes be prohibitive.
If it looks like your garden soil already has plenty of organic matter (i.e. not overly sandy with little structure), regular garden soil would likely be fine. But if you want to virtually guarantee a strong start to that garden and don't know (yet) exactly what you need, you can be pretty confident starting with a mixture of garden soil and compost.
Answer: This is a tough question.  Please give us a picture or two, Dotty!  To build up a plant bed now with the plants already established is dangerous for your plants.  Especially if you have woody perennials or shallow rooted plants like Azalea or Daphne.  Adding anything on top of those roots could easily kill plants that rely on shallow surface water/chemicals.  Even an inch too deep will kill them.  Woody trunks if covered with soil, mulch, rocks, moss...will be girdled eventually by bacteria that love the moisture.  It would be easier to redo the lawn, cutting the sod out and removing it.
Please send pictures, try to get a wide view so that we can see the slope and levels of lawn versus your plant beds.  Are these same plant beds next to your foundation?  If so another good reason to cut out lawn to lower the elevation to allow water to drain away from the foundation from plant beds and then out over the lawn.

How to level up low flower beds?


could someone please look at this? it doesn't seem quite right

Question: Comment to check
Not spelling out details for obvious safety reasons
Answer: Thank you for calling out the inappropriate comment! Those comments have been removed. Such comments are not welcome here at U&L.
Flagging the comment would be slightly better for these situations, as it leaves a "paper" trail (the flags) closer to the actual issue. One of the options there is: "It contains harassment, bigotry, or abuse.", which I think would have been appropriate. If you're not sure among the comment flag options, you can always choose the "Something else" option and describe the issue in the textbox.
Thank you again for bringing this to the community's attention!
Answer: I think that the dedicated way to solicit those who can actually decide whether things are quite right or not (iow the elected keepers of the code of conduct) consists in flag-ing the comment (clic on the flag at the immediate left of the comment) labeled Flag this comment for serious problems or moderator's attention

About the particular ocurrence you mention, I can only observe that the (quite high-rep and respected) contributor who could (rightfully) read some disgraceful personal attack did not flag that comment himself and, as part of some following comment, even explains why he did not.
[EDIT : reading from comments, I am wrong, he had actually reported.]
My opinion about this particular occurrence then stands in two parts :

Who would I be as a third party non involved to arbitrarily decide differently ?
If anyone else flags this comment and this comment is actually removed and since nobody (apart from mods) can tell who is responsible for the flag, wouldn't the original and a-priori sincere intention of the victim be somehow betrayed ?

On a side note, answers to personal attacks in comments are generally removed together with the inappropriate comment, this incidentally ruining any attempt from the victim to handle the situation according to… their own idiom… ;-)
This certainly contributes to stop flame-wars early but this should imho be adjusted when the personally attacked contributor is not known for fueling that sort of things.
Comment: @MarcusMüller :  Mybad then. I had not seen the flag colored, indicating that someone had flagged the comment (as I was used to see in other SE_Sites) and inferred that, since you were (kindly) taking care of the obvious offenser wealth you would have wished your comments to remain. After all, that is the principal point of my answer : I trust that kind comments from some known honest & respectful contributor following a personal attack can be much more profitable to the community than the removal of the whole suite of comments.
Comment: I did flag! I explained *why* I flagged, namely that such behavior can never be acceptable to a community (imagine how that would impress someone with less of a thick skin, maybe even an actually vulnerable person!), but my main worries do revolve around the person behaving that way – that's really not an OK change in state of mind… [for comparison, same person 4 months ago](https://interpersonal.stackexchange.com/a/28464/20658).
Comment: you're really flattering me there. I might have been to blunt in the comments I posted (and which are still there)


First Mobile Indie Game - Monetization Model. Ad based or in app purchases?

Question: We are a team of 3 (1 graphics designer, 2 developers). We're almost done with our first Android based indie game. Which monetization model will be suitable for us? We don't want to disturb users with a lot of ads (at this point we're thinking to put only banner ads) also, if we go with in app purchases, can we also keep ads as well? or is it a better practice to follow one model at a time? How much will it affect the user experience?
Comment: This is more of a development/business decision you need to make on your own. There's no *correct* answer to this. Typically in a situation like this, you'd make a list of the available options, then list the pros/cons of each and make a decision based off that list.
Comment: But I added it here because we're newbies in this field. Maybe some experience game developer here can share their experience? As to which strategy is more efficient, both in terms of User experience and revenue generation.
Comment: Sure, if there was a most efficient strategy, it would be *the* strategy to use. But user experience is very difficult to quantify and revenue generation has so many other factors, it would be near impossible to relate it to a specific monetization model. That's what I'm saying, there isn't a "best" way to do things. There's only "best for you". And that's not a general answer for everyone, it's specific to what you want and your game. Your question is probably "primarily opinion based" as it stands.
Comment: There really is no wrong answer so long as you don't break your gameplay (sell super powerful item, ads that block the screen midgame, etc.). It's all a matter of personal preference.
Comment: You may find this blog post from Flurry Analytics interesting (their free analytics app with event logging is really awesome by the way): http://blog.flurry.com/bid/99013/The-History-of-App-Pricing-And-Why-Most-Apps-Are-Free
Answer: Like other comments have said, its entirely a personnel decision. That being said, I would like to point out a few things:
If you decide to have ads, be careful with your buisness model you represent to the player. If you're charging to get the game (not releasing a free version) people may be a bit turned off that you're still showing them ads. That being said, ads on a free version of the game are golden. Several games out there have a free version that has ads that offers a paid version that doesn't.
As someone who gets almost exclusively free mobile games and frequently reads web comics, I honestly don't mind looking at ads for sites and games I enjoy if I know that this is how the developers make their money.
With microtransactions (in game purchases) its also important to understand if this works with your game model. Are there things you CAN sell to the player? Extra Lives, Experience/stat boosts, extra items, vanity items etc. If your game doesn't have anything like that then you might not have anything to really sell with microtransactions. You can also have these same items out there for an in game currency. (Check out how Guild Wars 2 does gems or Jetpack Joyride does its shop if you need examples) A common practice is to offer it for a somewhat ridiculously large number of in game credits or for a small real world amount (like $1 or $2).
It is possible to have both ads AND microtransactions HOWEVER I highly advise being very careful when doing this. You don't want to make the player feel like the entire game is a grab at their money, this will turn anybody off. It is very doable but just be mindful of what the player may think when they see these things. If you're not sure of what the player will think, download a few games for yourself and try to find good and bad examples (I have a feeling you already have a few of these on your mobile device) If you do decide this though, I highly suggest making a version that is ad free that is a paid version.
Ultimately it comes down to what game are you making and what kind of business decisions you want to make. This is entirely up to you. Coming on here and asking "What are some pros and cons?" is fine, but truth be told there is no golden ultimate answer here. (unless your game is named "golden ultimate answer")

EDIT: I just thought of something else.
Any team that makes the ads as a part of the game gets major props in my mind. I'm not talking about "Do so many surveys and you can get a free _!!!" I mean a pop up ad occurs and when you close it the character (if the game is an RPG) says something, like "Bloody ads, mess up my aim" or "Hey, that might be cool." if the player clicked on it. It may be too late for your team to do this since you said you're almost done (congratulations by the way), but it would be fun to see anyways. PLUS this gives added immersion since you would be making the character experience the same thing as the player. (Think something like in the Never Ending Story)
Comment: Thanks a lot. I was expecting something like this when i asked this question. Agreed that there is no "golden ultimate answer" still, suggestions like these can really help when we're finalizing our model. :)
I'll accept it as answer in a day or two, let me get some more insights from other developers here. :)
Answer: Being a gamer , what annoys most is too much ads . Avoid placing ads as much as you can if you want a successful game. Focus more , more and more on game-play . If game-play is awesome , anything is tolerated. People dont mind in-game purchases but keep in mind that these purchases should not in any case affect the actual game play , they should be more like customizations etc . Hope it works out for you guy :) Best of luck
Comment: Hello and welcome to GDSE.  This is not really and full answer, it's more like an short opinion of yours. It's more suitable as an comment. I understand that it's hard to answer this kind of question without opinions. You could try to open this up little more.
Comment: @TahaRushain You don't seem to realize that the goal of a game developer is not to develop a good game. It is to develop a profitable game.
Comment: @Philipp I do not agree. Primary purpose of a game developer is to develop a good game! If it pays well, then good for them.
Comment: @jazz I absolutely agree that the main goal of a game (or any other "creation") should always be quality (the definition of which varies depending on the medium) and not money. Games that are created purely to make money usually feel like "games that are created purely for money" - it always shows :) I hope your game is successful!
Comment: @Philipp Brother only good games are the ones that are profitable games.
Comment: You guys should follow both models in a little extent. Use both models in a well balanced manner , that not in any case ruins the game or annoys a casual player. You guys would make a good living if you make your clients (gamers) love your game.
Comment: @Philipp I disagree... "Profit" can come from SO many areas. drop the ads in game and make a landing page with ads... but if an app or game is bogged down with ads, it is unplayable. furthermore, i dont trust ads to be allowed to run code on my device. IMO ads are a deal breaker. one should provide demo content in the free version, with features unlocked for the paid version
Answer: Being a gamer myself,I would prefer IAP, but it wouldnt be as profitable as Ads
As everyone here said, it's up to you, but if you choose Ads, make sure they are subtle and don't spoil your games
example: You dont want an Ad where a user might touch it by mistake and ruin their gameplay :)
Comment: @AnitejBanerjee Can you provide some source to back up the claim that ads are more profitable than ingame purchases? Because I frequently heard the opposite.
Comment: Hello and welcome to GDSE. This is not really an full answer, it's more like a comment. This answer alone, without other answer's would not help anyone and that's why -1.
Comment: @Philipp : Ads are seen by everyone, and thus will multiply with the number of players. However, only a certain portion of players -- that spend enough time at the game -- will be willing to buy IAP.
Katu : Since he asked a question about a game, I thought I should tell him what a gamer would think. Yes, there were no numbers/facts, and I will take this into account next time :)


Help with phone upgrade

Question: Hi my question is how to upgrade to jelly bean? I have a Samsung Galaxy 2. I am use to Jelly bean that what my tablet is,so I am 1st time user of this phone I purchased. I was trying in google store to get my game on my phone and it said it was not compatible.So went in setting saw software update but when I tried to it said no firm ware. It is a second hand phone so I don't know what to do. I thought maybe if I could upgrade to jelly bean it all problems. Idk if I could find a site that has a free upgrade download. If you know a site I can do this please let me know. I don't have a USB cable just a home charger, do I need one? Ty in advance, Wendy
Comment: Check if http://www.cyanogenmod.org could interest you.
Comment: Sammobile.com has alot of downloadable firmwares to flash via recovery
Answer: What you need to do is root your phone and flash a custom ROM. I'll try to give you a pretty detailed answer to your question. The S2 is pretty old so I'm sure you're not concerned about voiding any warranties, correct? If it is under some carrier (Sprint, ATT, etc.) waranty, then you're pretty much out of luck unless you don't care about voiding it. There are ways to un-flash smartphones, but I would't recommend it. Anyway, onto flashing....
Rooting and flashing a new rom is a technical task so if you're not up to it you could probably find a friend (or someone on Craigslist, etc.) to root it and flash a custom rom for you. It will definitely take a few hours since it's your first time doing it, and it can be a real pain if you run into a problem. I rarely have, but you never know. You can always come back to the forum and post the problem or ask on the YouTube channels recommended below.
If you decide to procede, I take no responsibility if you break your phone. First do a YouTube (or Google) search for "Flash CyanogenMod 11 4.4.4 (Insert Carrier Name Here) Galaxy S2". You should be able to look through a few pages and find a (well written) tutorial that will guide you through rooting your S2 and flashing a custom rom.
Tip: Verify that you're able to download all of the necessary files before you even plug your S2 into your PC and start to root it (and yes, you will need a USB cable). Most of the headaches I've encountered had to do with getting half way through the install process only to come across a dead download link, and then not being able to easily find the exact same file I needed somewhere else. Also, some of the roms have some bugs. Most of them don't but it is something to be aware of if something like your GPS doesn't work. Once your phone's rooted you'll be able to just reboot it, boot into recovery mode, and flash another rom (without having to completely re-root your phone). You may have to do another search for how to re-boot into recovery mode for your specific cell phone carrier. You should be able to simply turn off the phone and then when you turn it back on, keep holding the power button down instead of letting it go in addition to the volume down button. Then just repeat the steps from the tutorial page (definitely bookmark the tutorial, in case you ever need to refer back to it) to flash a different rom.
I really hope this post helps you understand the tech lingo a little bit better and that you're able to get your S2 rooted easily. I didn't know anything about rooting a few years before I rooted my first phone, and I learned nearly everything needed within the first day! If you set aside a day or two to root your phone, flash a custom rom, and explore all of the settings of the new rom you'll be glad you did. It sucks if you're out and about and need to change a setting but have no idea where it is because all of your settings menus changed.
If you have any issues or questions, please post back here and I'll help as much as possible. I've rooted many phones and flashed a couple dozen roms so I do have a bit of experience with the process. I was actually going to do a short tutorial myself but StackExchange shut me down and said I could only use two links in my post because I didn't have enough reputation points :(.
Good luck and I hope everything goes smoothly for you!
Comment: This one is big to read. Anyway, IMHO, OP asked for a upgrade which should be solved out by providing steps. That said, what you mentioned here isn't steps to upgrade but to prepare for them (with exception of some). I don't think that would even count as a partial answer, let alone a complete answer. The gist should be as a comment in the question. But that's just my opinion.
Comment: Like I said, I couldn't make a tutorial with all  of the steps because stackandroid limited my download links and there are many links that are required to root and flash a phone. It is as complete of answer as she's going to find, and a lot more complete than the simple one line comments that she already had. I also did provide the steps, just not in a 1, 2, 3 format. And yes, it's a long post but if I was in her shoes I would rather have four paragraphs that explained everything I needed in detail than a sentence that didn't!

Help with phone upgrade


Facebook access_token for ads

Question: I have ad campaign and want to receive stats for it with this facebook tutorial.
But everywhere I see access_token required. And I don't understand where I can find it for me as developer for ad.

I've used this for user access token, and I see there app token and page token. But no access token for ad.
So my questions:
1. Is it possible to get data from ad campaign as developer?
2. How can I generate access_token for developer for ad?
Answer: These are the steps you need to follow to get started:

Visit https://developers.facebook.com and create your app if you haven't already
Visit the Marketing API > Tools page (put your APP ID in):
https://developers.facebook.com/apps/<YOUR_APP_ID>/marketing-api/tools/
Create a sandbox ad account and generate a sandbox token to test with (see screenshot: https://i.stack.imgur.com/JOyMF.jpg)

Once you're ready to go live you'll need to then:

Visit the Marketing API > Settings page (put your APP ID in): https://developers.facebook.com/apps/<YOUR_APP_ID>/marketing-api/settings/
Link your ad account
Go back to the Marketing API > Tools page and generate a real access token
Comment: But what if I have ads, but doesn't have app? I mean I have three sites, and ads for this three sites. But I have no apps for this sites. Does it mean that I can create one app to manage unlimited number of ads?
Comment: You can assign multiple ad accounts to one app or have separate apps for each. The choice is yours.

Facebook access_token for ads


Formula fields and short circuit evaluation with references to null lookup fields

Question: We were always under the assumption formula fields used short circuit evaluation for boolean logic. But we're running into an issue we've never seen before that seems off.
Assume an object has a lookup field to another object, Lookup__c that is NULL.
Should we be able to use this guard condition in an AND function:
AND( NOT(ISBLANK(Lookup__c)), Lookup__r.Num_value_field__c > 70)

Salesforce seems to still evaluate the 2nd argument to the AND even though the 1st argument evaluates to FALSE, causing an error.
For example, if I set the following checkbox formula field on the same object, I would assume it would always evaluate to TRUE:
OR (AND (NOT(ISBLANK(Lookup__c)), Lookup_r.Num_value_field__c > 70), TRUE)

But the checkbox always evaluates to false. We're assuming that it's due to the 2nd argument to the AND being evaluated with a null reference.
Also as a double-check, we also checked the following formula, which did short circuit and doesn't result in an error:
AND(FALSE, NOT(ISBLANK(Lookup__c)), Lookup__r.Num_value_field__c > 70)

One other thing we tried is using an IF as a guard, which does work:
IF (ISBLANK(Lookup__c), FALSE, Lookup_r.Num_value_field__c > 70)

Also, it doesn't matter whether we use ISBLANK or ISNULL
Thank you for any input.
Comment: This is working as expected in cross object formula lookup fields.
To avoid these type issue, you need to use the IF statement. Refer the https://help.salesforce.com/s/articleView?id=000381947&type=1
Answer: ive always used lookup__c != '' to make sure it works.
could you try this?
AND(
   lookup__c != '',
   Lookup_r.Num_value_field__c > 70
)


Difference between "classical" and "classic"

Question: What's the difference between classical and classic? Should we say classic content in textbooks or classical content in textbooks?
Comment: [mystic vs mystical](https://english.stackexchange.com/questions/569565/adjective-usage-of-mystic-vs-mystical) is like [magic vs magical](https://english.stackexchange.com/questions/215878/magic-versus-magical), [classic vs classical](https://english.stackexchange.com/questions/48608/difference-between-classical-and-classic) and [comic vs comical](https://english.stackexchange.com/questions/57060/comic-vs-comical) ?
Comment: are [gold/en and wood/en](https://english.stackexchange.com/q/433757) like [mystic/al](https://english.stackexchange.com/q/569565), [classic/al](https://english.stackexchange.com/q/48608), [magic/al](https://english.stackexchange.com/q/215878), [comic/al](https://english.stackexchange.com/q/57060)?
Answer: First, we should look at the definitions (from Google)
Classic:

adjective /ˈklasik/
Judged over a period of time to be of the highest quality and outstanding of its kind

a classic novel
a classic car

(of a garment or design) Of a simple elegant style not greatly subject to changes in fashion

this classic navy blazer

Remarkably and instructively typical

I had all the classic symptoms of flu

Classical:

Of or relating to ancient Greek or Latin literature, art, or culture

classical mythology
(of art or architecture) Influenced by ancient Greek or Roman forms or principles
(of language) Having the form used by the ancient standard authors

classical Latin

Based on the study of ancient Greek and Latin

a classical education

(typically of a form of art) Regarded as representing an exemplary standard; traditional and long-established in form or style

a classical ballet

Of or relating to the first significant period of an area of study

classical mechanics

Relating to or based upon concepts and theories that preceded the theories of relativity and quantum mechanics; Newtonian

classical physics

In both cases there is a sense that classic/classical relates to something typical or held in some kind of esteem (classic cars are outstanding, Greek and Latin are considered important and prestigious to learn). However, classical is used to describe things that are much older than things which are merely "classic". Classic Rock music is from the 70s while Classical music is from centuries ago.
In the case of a textbook, it would depend on the contents of the textbook, such as whether the textbook is describing something with a long tradition (classical algebra) or whether it is a particularly well-written example fondly remembered by the students who used it (a classic text about algebra).
Comment: I don't think the distinction between 'classic' and 'classical' has anything to do with age as you suggest. The Classical period in music is so called because of the concurrent movement towards ideals associated with the original [classical period](http://en.wikipedia.org/wiki/Classical_antiquity) (8th-5th centuries BC), not because the age in which the music was written is itself considered 'classical'.
Comment: @Snubian, 'The term "classical music" did not appear until the early 19th century, in an attempt to "canonize" the period from Johann Sebastian Bach to Beethoven as a golden age.' Golden age is considered
Comment: * this period *is* considered classical in music. And it is an older period; I am not so sure that the ideals of the classical antiquity are necessary to explain the name.
Comment: Also note the idiom "That's a classic!", for a typical joke or funny situation
Comment: I used your answer to answer [this question](http://discuss.area51.stackexchange.com/questions/4618/) (on area51.stackexchange.com).  Thanks for helping me!
Answer: The adjective classic is defined as 'exemplary of a particular style' or 'exhibiting timeless quality'. For example, a 'classic car'.
The adjective classical, in the sense you describe regarding textbooks, means 'of or pertaining to established principles in a discipline'. For example, 'classical mechanics'.
So to answer your question, 'classical' would be the word to use.
Answer: 'The Cambridge Guide to English Usage' has a good article on this. Here's an extract:

While classic has become a more popular and subjective word, classical
  maintains the higher ground. It is suffused with a sense of history
  and great artistic traditions: classical music is associated with a
  period of outstanding music in western Europe in C18 and C190; and
  classical ballet embodies what for many is still the acme of balletic
  technique, developed last century.

The article goes on to consider the use of classy, concluding that:

Classy is more direct and down-to-earth however; so it can probably coexist with classic for some time to come.

(FWIW, I like to think of music being divided into formal and informal, rather than classical and popular.)


How can I find a Qt metaobject instance from a class name?

Question: Is there a way to find the QMetaObject instance of a class, given the class name? what I like to do is to load objects from disk, but for this to happen, I need a way to retrieve a QMetaObject instance using the name of a class, in order to use the QMetaObject to create an instance.
Answer: You should be able to do this with QMetaType. You might need Q_DECLARE_META_TYPE() and/or qRegisterMetaType() to make your types known. Then it should work roughly like in this example from the link:
 int id = QMetaType::type("MyClass");
 if (id == 0) {
     void *myClassPtr = QMetaType::construct(id);
     ...
     QMetaType::destroy(id, myClassPtr);
     myClassPtr = 0;
 }

Answer: I have been facing the same problem recently. I needed the metaobject without having to create an instance of the class itself. Best I could do is to create a global / static function that retrieves the qmetaobject given the class name. I achieved this by using QObject::staticMetaObject.
QMetaObject GetMetaObjectByClassName(QString strClassName)
{
    QMetaObject metaObj;
    if (strClassName.compare("MyClass1") == 0)
    {
        metaObj = MyClass1::staticMetaObject;
    }
    else if (strClassName.compare("MyClass2") == 0)
    {
        metaObj = MyClass2::staticMetaObject;
    }
    else if (strClassName.compare("MyClass3") == 0)
    {
        metaObj = MyClass3::staticMetaObject;
    }
    else if (strClassName.compare("MyClass4") == 0)
    {
        metaObj = MyClass4::staticMetaObject;
    }
    else if (strClassName.compare("MyClass5") == 0)
    {
        metaObj = MyClass5::staticMetaObject;
    }

    // and so on, you get the idea ...

    return metaObj;
}

See : http://doc.qt.io/qt-5/qobject.html#staticMetaObject-var
If somebody has a better option, please share !
Answer: You can store the MetaClass instances you will need in a Hash or Map, and then retrieve them via whatever name you stored them under
Answer: For your case the appropriate solution can be using Qt plugin mechanism. It offers functionality to easily load shared/dynamic library and check if it contains implementation of some desired interface, if so - create the instance. Details can be found here: How to Create Qt Plugins
Answer: You can also take a look at the function: QMetaType::metaObjectForType which

returns QMetaType::metaObject for type

Update: That's my code, it create a class by class name. (Note that the class must be registered  with qRegisterMetaType (or is QObject base)
int typeId = QMetaType::type("MyClassName");
const QMetaObject *metaObject = QMetaType::metaObjectForType(typeId);
QObject *o = metaObject->newInstance();
MyClassName *myObj = qobject_cast<MyClassName*>(o);

Update 2: I have forgot to say. Yout class's constructor must be marked as Q_INVOKABLE


replicate master/slave without disturbing master for dump

Question: Is there a way to replicate master/slave without disturbing master for dump like mysqldump or cold copy of data files? I'm ok to bring down the instance only once for master to enable log-bin. But there is no feasibility for dump or even cold copy. As I have 400G of data and 1min down time only.
Comment: Do you run all InnoDB or all MyISAM or a mix of both?
Comment: All are in innodb
Comment: What version of MySQL ???
Comment: It is 5.0.77-log
Answer: I would recommend Percona's Xtrabackup for this, especially since you mentioned all of your tables are InnoDB. From the page:

Percona XtraBackup is designed to make backups a seamless procedure without disrupting the performance of the server in a production environment.

The tool will allow you to take a backup without locking innodb tables. It will do a lock to copy any MyISAM tables (such as the tables mysql in the mysql database) but those shouldn't take long.
I cannot tell you how long it will take on 400GB database, but it should do it without downtime.
Comment: yeah.. thats the last option I have, if this is the case on any mode of replication.
Comment: eh? You're going to have to get a full backup of your 'master' to set up any replication.
Comment: yep I get that. But my peers having a strong objection on this concept in HA. The underlying concept is. For any HA either via cluster or replication if primary is down and secondary takes over the threads as a failover and inorder to rebuilt the primary do we need to get the dump from failover node? only in terms of backup? "I say yes,.. thats the only option by taking dump from failover node and construct the failed primary by taking down time in non-peek hrs..
Comment: xtrabackup won't require you to take down any nodes, especially if you don't have myisam tables.
Comment: Yes, I have done that earlier, for myisam 90GB data it goes for a toss too... I don't have to worry abt that one though. But I was checking is there an option to automatically pick data from failover node to primary without any binary logs or any backup methods. Just wondering what kind of replication would do this.. :(
Comment: I have done that one earlier.. for myisam 90 GB data it goes for a toss.. and I don't have to worry abt that as I don't have them. I was curious to see if any replication module has a way to automatically absorb from master.


How to flash Magisk-x.y.z.zip using fastboot without using TWRP?

Question: Is it mandatory to use twrp to flash Magisk. Can it be flashed using fastboot
Comment: you probably can't flash magisk with fastboot
you must have twrp installed or any other custom recovery..
Thanks..
Answer: You probably meant fastboot mode.
And no, Magisk cannot be flashed using Fastboot mode. It is a zip file and not an image file that you can just flash to a partition.  If you want to use fastboot, you should consider patching your boot image using Magisk Manager and then boot that image using fastboot boot command.
fastboot boot magisk-patched.img

Or if you are sure you have the correct boot image, you can flash the patched image too:
fastboot flash boot magisk-patched.img

Comment: @Talespin_Kit [this way](https://topjohnwu.github.io/Magisk/install.html#boot-image-patching)
Comment: You need the stock boot image. Then you can use Magisk Manager to inject Magisk into the boot image. And then flash/boot the image which will load magisk init commands when the device starts up.
Comment: Thanks. Fixed typo. Magisk Manager is a apk file. How to use Magsik Manager to rewrite the boot image on a non-rooted phone while i am trying to root the mobile using Magisk.


Why aren't shape of galaxies depicted as a funnel?

Question: Let's say if a galaxy is moving, shouldn't it be shaped like a funnel? I am saying this because it would take considerable time for the outermost star to know that the center of gravity has shifted. For example, if milky way's radius is 100,000 light years, there is possibly no way for the outermost star in our galaxy to know that the center of gravity has moved before 100,000 years. So taking a circular symmetry, the only thing that comes to my mind is a funnel-like shape.
Comment: What you're forgetting is that the star and the center of gravity are moving at basically the same speed, so from the star's reference frame, the center of gravity is not really moving.
Comment: Why are you assuming that the galaxy's motion originates at its center of mass?
Comment: I guess you are probably right. But things will change in case of accelerated motions, right? Such as in the event of collisions of two galaxies?
Comment: You should address your replies with the @ sign. Otherwise members are not notified.
Answer:
Let's say if a galaxy is moving, shouldn't it be shaped like a funnel? I am saying this because it would take considerable time for the outermost star to know that the center of gravity has shifted.

Moving with respect to what?
Suppose the galaxy's center of mass is moving at some velocity respect to some external object. You can always find some other external object for which the motion of the galaxy's center of mass is in exactly the opposite direction. Or yet another object for which the galaxy isn't moving at all.
This concept of relativity dates all the way back to Galileo. Galilean relativity is implicit in Newtonian mechanics. Einstein went one step further and made relativity a central concept in his theories of special and general relativity.
One thing that is absolute in Newtonian mechanics and special relativity is acceleration. This concept carries forward to some extent to general relativity. Suppose a galaxy is on a collision course with another galaxy. When the galaxies are far removed from one another, all of the stars in one galaxy experiences more or less the same (very small) gravitational acceleration toward the other. But when the galaxies get close to one another, the stars in one galaxy closest to the other galaxy experience a much greater gravitational acceleration than do the stars in that galaxy that remain well removed from the other galaxy.
These tidal accelerations have the potential to tear galaxies apart, but not into a funnel shape.
Comment: "Moving with respect to what?" I can answer this one. There is actually a rather special frame of reference, namely the frame of the cosmic background radiation. It is not relevant to the question at hand, though.
Comment: If a smaller galaxy hits a larger one in tbe center with a high speed and momentum, this would create a funnel, would it not? And this would be a unique opportunity to study the galaxy rotation mystery (dark matter, etc.). So is there a search for such an occurrence?
Comment: @safesphere:  Sure, we've found many [interacting galaxies.](https://en.wikipedia.org/wiki/Interacting_galaxy)  And yes, galactic interactions have been studied to try to understand dark matter;  in particular, read up on the [Bullet Cluster.](https://en.wikipedia.org/wiki/Bullet_Cluster)
Comment: @MichaelSeifert The Bullet does look like a funnel: https://upload.wikimedia.org/wikipedia/commons/e/ea/Bullet_cluster.jpg
Answer: You are forgetting about Newton's 1st law. Objects in motion stay in motion unless an outside force acts on it. The stars in the galaxy are already moving relative to the center of mass, and so they will keep up with the center of mass by default. They don't need information about the motion of the center of mass of the galaxy because objects don't need forces to make them move at a constant velocity.
It's kind of like asking why I don't drag behind my car when I drive on the highway. Once me and my car are both going 60 mph, there doesn't even need to be a force keeping me going because of Newton's 1st law.


delete drill layer in eagle without redoing board

Question: When I go to make my own circuit boards with eagle, after saving, I run the drill-aid.ulp script so eagle can convert all over-sized drill holes to small size. It helps me with drilling. I then saved my board again. I did this a few days ago.
Now this time, I load the same board and I want to undo that operation very quickly. I tried selecting the layers box and I scroll all the way down to:
116 CenterDrill

When I select Del, I get the message:
Layer '116 CenterDrill' is not empty.

Because I have at least a few hundred of these to remove, doing it manually will be a pain in the butt.
Is there some easy way for me to do this? even if it means me inventing some sort of script? I want the board to once again be at the state just before drill-aid.ulp was executed.
Answer: I just figured it out. I had to hide all other layers, select the entire board (aka drill layers) then delete them then re-display the other layers.


How can I get an email notification when one on one meetings I calendar are "declined"?

Question: Google calendar question. I need to periodically meet with senior leaders one on one. These meetings are difficult to keep and are frequently "declined" in favor of other urgent priorities. I do not want to be constantly checking if they are still on or declined and frequently I discover they've be declined the day before or day of when I'm reviewing my calendar and preparing. It might have been declined weeks earlier but I just didn't realize. I'd like an email when these meetings are declined so I can get busy rescheduling them. It would be great to condition these notifications by name or even by meeting size and regardless if I set the original meeting or the executive did.
Comment: Google calendar, by default, informs you when meetings are accepted or declined. Check your spam folder.
Comment: To clarify: Are you using the "normal" Google Calendar, or are you working within Google Apps (for Work)?
Comment: Nothing in the spam folder (could be for a number of reasons). Are you suggesting  some sort of filter approach to pull up the ones of interest and keep them in the email and out of wherever they are going now?Google Apps for Education
Comment: No, just wondering why you're not already receiving cancellation notices. I'm afraid I don't have a Google Apps account, so probably can't help you there.
Answer: These directions apply to both consumer (@gmail.com) and enterprise Google accounts.
To ensure you are configured to receive email notifications when events on a calendar are canceled please follow the steps below. If you have created additional calendars beyond the primary calendar, you may need to repeat these steps for each calendar.

In a computer's web browser go to calendar.google.com and sign into your account if you aren't already
Click the gear icon in the upper right
Select Settings from the Drop down menu
Select Calendars in the top menu
Click Edit notifications for the calendar you wish to check the settings for. This will usually by your primary calendar, and it will usually be named after you
Check the box for Email on the line marked Canceled events. You may wish to review the settings for the other types of notifications on this page
Be sure to click the Save button
Click Back to calendar

Note that these notification emails are from the calendar service to you, not from the person that canceled the event. These emails will be sent to you regardless of if the person cancelling the event decides to notify you of the cancelation or not.


Print Resolution

Question: I've made several collages and wanting to print an 8 x 10 I'm constantly told "there will be a resolution" problem.  I guess I'm ignorant of what happens when I reduce the "huge" jpg to a smaller size.  I just assumed that the smaller the picture the more pixels - apparently NOT!  How do I correct this?  Thank you.
Comment: _How_ are you reducing the "huge" jpg?
Answer: The smaller the picture is resampled, the fewer the pixels.
Image size is dimensioned in pixels.  24 megapixels might be 6000 x 4000 pixels (6000 x 4000 = 24 million).  In uncompressed data, there are 3 bytes per pixel (the most common normal 24 bit color), but JPG compresses the file significantly smaller.
To print 8x10 inches at an optimum 300 pixels per inch is a size of
(8 inches x 300 dpi) x (10 inches x 300 dpi) = 2400x3000 pixels.
Fewer than that is less than optimum.
300 pixels per inch is optimum (more won't help color photo printing).
200 pixels per inch might be acceptable quality, but not best.
100 pixels per inch is considered too few pixels.
Comment: Depending on the print tech and media, the level of detail, and degree of close scrutiny, it's not _necessarily_ true that more than 300ppi "won't help".
Comment: Also note that typically, _pixel_ is not equivalent to _byte_. Given a typical RGB image with no compression, 24 megabytes is closer to 8 megapixels, or something like 3465x2310. Unless you were referring to a _monochrome_ image...
Comment: mattdm, agreed, there are other situations (but Only other in JPG files is grayscale). I was assuming RGB JPG photos. Lineart printing is better at 600 dpi, but that is not JPG.  twwlberg, yes, I did mispeak, I meant 24 megapixels, and did equate it to 6000x4000 pixels. Edited now.
Comment: Many printers have a base resolution of 360 ppi, or even 600 or 720 ppi. For such a printer, an image that will yield higher resolution than 300 ppi will show more detail (i.e. with a 720 ppi printer an 8x10 inch print made from a 5760x7200 pixel image will show more detail than a print made from a 2400x3000 pixel image).
Comment: @MichaelClark True. And it's not just detail, Most printer driver interpolate between their native resolution by using nearest neighbor, a relatively crude technique.  While rare, I've seen instances where printing at a different (higher or lower) resolution than the native printer can create moire. Striped shirts, and regular patterns such as building facades are more likely to show it. Even then it's quite rare and won't show up except on the sharpest of images. But if you run across it resample the image before printing.

Print Resolution


Assigning values from one polygon to second polygon if located within first using ArcGIS for Desktop?

Question: I have two layers of polygons. I would like to know if there is a way to assign a value from
a polygon in the first layer to any polygons from the second layer that fall within that polygon?
Comment: the attribute mapping tool works nicely if there are not too many that you want to automate it. Edit your original question with more info (how many polygons/ type of solution).
Comment: Spatial Join answer sounds like it will fit the bill, however other options include Identity, Intersect and Union depending on what you want to do with polygons that partially overlap or are outside. Can you draw a picture of an example of what you want to do with polygons within, part overlapping and outside the *from* polygons.
Answer: The Spatial Join geoprocessing tool will do what you're looking for.
With the tool parameters something like this

Target Features: polygon dataset to which you wish to join attributes.
Join Features: polygon dataset from which the attributes will be transferred IF they meet the Match Option (Spatial Relationship).
Output Feature Class: feature class to which the result of the operation will be written.
Match Option: WITHIN


Can you identify the model of this faucet?

Question: I know the make is American Standard.  It has a spray handle, and is 5 years old or less.  I need to buy O-rings for it, and want to be sure I'm getting the right ones.
Answer: You say you need "o-rings" but not specifically what part is the issue. If you take the part(s) to a good plumbing shop (a "good plumbing shop" is specifically a different thing from a big-box retailer) I would bet they can find what you need. The model number will be of little to no assistance to them, they know the parts by sight.
American Standard has manufactured literally hundreds of different faucets over the recent years, and regardless of the model number many of the parts are common.
The closest in American Standard's current catalog looks like this:


Yahoo UI the popup implementation with YAHOO.widget.Dialog

Question: I used the Yahoo.widget.dialog to implement a popup window. Currently, it popups only on the page which is belongs. If I am working on the other (tab browser) pages. The popup window will be not seen.Could somebody supply some help for this ?Thanks
Answer: You could either switch to window.alert() or use window.open() to open a new pop-up window containing your content.
Neither one is something I'd personally want to experience, but those are your two options for opening a pop-up outside the page. Window.open will get caught by many pop-up blockers so you'll need to watch for that.


Slack API: how do I tell if a message is coming from a single user private channel to my Slackbot?

Question: How can I detect if a message is from a user who is chatting with my bot in a private channel (DM with only the bot) using the Event API?
Comment: Your question is too general. Please provide some specifics about how your slackbot is setup, e.g. are you using the RTM API or the Event API for your bot? What information are you currently getting from the user when he sends a DM message?
Answer: Check the first letter in the channel id.  If it starts with D it is a DM channel. If it starts with C it is a public channel.
For example, D2AH456 is a DM channel, whereas C234F56 is a public #channel
Comment: Gonna add from another post which I now can't find. `G` is for private or group channels


Sourcing vintage style pedals

Question: Looking for a replacement set of pedals for the image shown below (EU/DE). Came off a Diamant Rennrad, not an expensive bike but would like to keep the styling similar to the original. I've seen a couple for sale on ebay (40-50 euros), but wondering if anyone has some other sources for old style pedals?
Comment: I suspect this question will be closed as Shopping, please don't take it personally.  Also consider that pedals of this vintage were not disposable, they were intended to be serviced.   Consider servicing them to extend their life time.  "how to service a pedal?" could be a good on-topic question.
Comment: https://velo-orange.com/collections/pedals
Comment: @Criggie I had been considering this also, so thanks for the reassurance about servicing the pedal.
Comment: And the answers 100% reflect the shoping nature of the question. With links to shops that are likely to rot, not actually be offering the pedals now or in future, or be just advertising a particular seller.
Comment: To illustrate the point, at the moment the Velo Orange pedals are all sold out
Answer: MKS makes vintage style pedals that are available on Amazon.de
This one is a aluminum. A little nicer than the original steel.
MKS Pedale Sylvan Touring, Silber, 2 Stück

Another old style
MKS Pedale Sylvan Road, Silber
Answer: Please have a look at the german equivalent of Craigslist, an online platform to buy and sell used items
https://www.ebay-kleinanzeigen.de/
There are plenty of old bicycles and related items, with some luck you can find someone having bicycle parts lots and they will ship them to your location.
Comment: @VladimirF Its not really an seconhand shop, its the german equivalent to craigslist.
Comment: I found it helpful and is currently my best option
Comment: How is this different from any othe bicycle secondhand shop?
Comment: The worse. You should not really answer with a link "this is a local version of a page where people offer old stuff, you might find it there if you are lucky". If it were a real shop, there would at least be the possibility of you knowing they stock such pedals.
Comment: I guess the answer was poorly written, but rather useful: the bicycle is of german breeding, it is very worthwhile to check the "online garage sales" type of sites.

Yes, the OP may contact a bicycle shop in Germany, with pandemy and so on they may be used to online sales. However, the hassle of shipping internationally may be too much for a shop (with all the strings attached to a commercial transaction, the shops bear all the risk), while for a private may be easier (and usually without warranties, so the buyer bear the risk)

Sourcing vintage style pedals


How to load pictures from a USB drive into a localhost html page

Question: So I'm trying to setup a display using this shifting tiles animation. I'm not putting it on a website, it's just going to be used on the local raspberry pi to display on a TV (http://localhost/) so I'm not worried about security. I've got it working by adding a few photos into the /var/www/html/ directory. But I'd like to be able to fill up a large flashdrive with 1000's of photos and randomly pull from that. My problem is I can't seem to get the permissions to do so. Are there any simple ways to read files from a usb drive?
Comment: what happens if you add a link to the USB drive into the /var/www/html/ directory?
Comment: @Michael, to add a link, do something like this: `ln path/to/target linkName`. You could do this for each picture, or add a link directly to the folder containing all the pictures.
Comment: well I think my issues are with permissions. Won't the link not work if www-data doesn't have permission to read/write on the USB?
Answer: Try 'sudo' to copy or link the files as 'root' to bypass permissions.
e.g.
sudo ln -s /[flashdrive-path]/*.jpg /var/www/html/
A neater way may be with relative path links, e.g. something like
sudo sh -c 'cd /var/www/html; ln -s /[flashdrive-path]/*.jpg .'
You could then change ownership to www-data using 'sudo chown on the symlinks'
If you still have permission problems, and you're not worried about security, you could make the image files and sub-directories readable by all, e.g.
chmod -R a+r /[flashdrive-path]/*


Regarding a priori propositions

Question: How is "All bachelors are unmarried males" an a priori judgement? For it to be a priori there has to be an innate concept of bachelor-ness which evidently man does not have. In order to acquire this concept, the mind is exposed to a variety of stimuli in the forms of words or other didactic methods by which one learns the concept of bachelor-ness. This would make this an a posteriori statement (derived from experience) rather than being a priori. Indeed what I'm claiming is that why do we insist on calling this statement or any other statement 'a priori' when obviously the content of these statements is not known to us at birth.
Comment: This is not how "*a priori*" is defined. It is not that the concepts involved are supposed to be innate, it is controversial whether innate concepts exist at all. They can be as empirical or culturally relative as one wishes, and require as much experience to acquire as one wishes. It is that *once they are in place* no further empirical inquiry is needed to settle whether the statement is true or not. The meanings (or rules of usage, if one prefers) of concepts themselves are enough. In contrast, no mastery of concepts "salt", "dissolve" and "water" will tell us that salt dissolves in water.
Comment: I see. Thanks for clearing this up.
Comment: It is not; it is usually considered [analytic](https://en.wikipedia.org/wiki/Analytic%E2%80%93synthetic_distinction).
Comment: It's an analytic a priori proposition. Which means to say that the predicate is contained within the subject of the proposition. And the concept itself requires no empirical verification which is why it's characterized as an a priori judgement.
Comment: I am with Mauro here.  It is analytic, but acquired.  The concept requires meaning about social concepts like marriage, which can only come from external evidence.
Comment: @Conifold I disagree with your example. With a sufficient knowledge of salt, water, and dissolve, one could deduce that salt will dissolve in water, since salt is an ionic compound, and water is a polar solvent.
Comment: @gardenhead "Sufficient knowledge" is not part of those concepts, they were in use long before people knew what "ionic compound" or "polar solvent" are. It took a lot of empirical inquiry to get from salt and water to that, indeed, much less is required to verify that salt dissolves in water.
Comment: @Conifold But you specifically said no mastery of these concepts would allow one to deduce the conclusion. But this is clearly false, as I have demonstrated.
Comment: @gardenhead You misunderstand the term "mastery", it amounts to correctly using the words in generic contexts, nothing more.
Answer: Contrary to what Geoffrey wrote, "bachelors are unmarried males" is an a priori proposition. Moreover, it is one of the most common examples to explain the difference between a priori and empirical statements.
See https://iep.utm.edu/apriori/:

The terms "a priori" and "a posteriori" are used primarily to denote
the foundations upon which a proposition is known. A given proposition
is knowable a priori if it can be known independent of any experience
other than the experience of learning the language in which the
proposition is expressed, whereas a proposition that is knowable a
posteriori is known on the basis of experience. For example, the
proposition that all bachelors are unmarried is a priori, and the
proposition that it is raining outside now is a posteriori.
The distinction between the two terms is epistemological and
immediately relates to the justification for why a given item of
knowledge is held. For instance, a person who knows (a priori) that
"All bachelors are unmarried" need not have experienced the unmarried
status of all—or indeed any—bachelors to justify this proposition. By
contrast, if I know that "It is raining outside," knowledge of this
proposition must be justified by appealing to someone's experience of
the weather.
Comment: Finally! An unconvoluted answer. Thank you.
Comment: Question: are there any example of analytic a priori propositions, that are not just "true by definition"?
Comment: By definition, an analytic statement is one that is true or false by definition. If the truth of a statement cannot be determined by the definition of its terms, it isnot analytic but synthetic. Most philosophers and scientists would deny there is such thing as synthetic a priori propositions (which tells you something more than the definition of the terms (synthetic), but yet can be known without empirical investigation (a priori).
Answer: 'All bachelors are unmarried men' is not an a priori judgement and is not generally regarded as such.  It is an analytic judgement, i.e. a  judgement which is true by virtue of the meaning of words. That is, if one regards the notion of analyticity as in good order in the light of Quine's criticisms in 'Two Dogmas of Empiricism'.
The analytic and the a priori are quite distinct from each other. (Kant claimed that analytic truths can be known a priori but he had a different notion of the analytic.) I know that 'All bachelors are unmarried men' is true because I have, through a process of experience (how else?), learned the language in which it is expressed or formulated. It is indeed as you intimate, a truth known (and knowable only) a posteriori. So your comment below, 'It would seem from this answer that no linguistic judgement can be characterized as a priori', is dead right: no linguistic judgement can correctly be so characterised. An a priori judgement is one which is known prior to or independent of experience. This agrees with your own characterisation of the a priori.
You ask in your comment: 'Then what would actually be characterized as a priori?' It is an open question whether anything is knowable a priori. Is there a non-experience-dependent way of coming to know something?
Let's think. Given perceptual experience it might be the case that in reflecting on one's experience one derives non-experiential knowledge. I know perceptually, i.e. by experience, what green and red are and what kinds of thing can be coloured. By reflection, and not as a matter of experience, I also know that nothing can be green and red all over at the same time. Without experience I could not have this knowledge but, given experience of the two colours, I can reflectively derive this further item of knowledge non-experientially. If non-experiential, then a priori. I have taken this suggestion from ch. 6 of Quassim Cassam's The Possibility of knowledge, Oxford: 2007: 195. Cassam extends the a priori beyond this example but I cannot give a full account of his view of the a priori here.
Comment: Then what would actually be characterized as a priori? It would seem from this answer that no linguistic judgement can be characterized as a priori.
Comment: I have revised the answer to provide a fuller response that takes note of your comment.
Comment: What about prophecy?  Is that independent of experience or by creating something tangible with the mind one is creating an experience?  What I mean to say is let's say I say the answer lies here = "appositive deixis" (read Parallax View randomly) ..and I read about miracle of dove yesterday ..or I read the Book of Mormon in random pages and read in line..if you do not believe you are not a member of this church..then read about Baptism..then learn the Chinese word for Baptism..anyway.  What I mean is if I had no knowledge of what "appositive deixis" was, but its relatable..is that a priori?
Comment: This is a bad prophetic example, but on a general level, while perhaps innate a/o transcendent, is it a priori or a posteriori ? Perhaps not such a bad example considering HERE is innate in the idea of Deixis hahahaha.  If you read the prior paragraph https://books.google.ca/books?id=je702bo2Pl8C&pg=PA125&lpg=PA125&dq=appositive+deixis&source=bl&ots=r7DKX7Xms2&sig=ACfU3U28JBLjRdMwO2nA8ByujHfhqpWwLQ&hl=en&sa=X&ved=2ahUKEwiI9OOM49XtAhXUtp4KHRLVCNwQ6AEwAHoECAEQAg#v=onepage&q=appositive%20deixis&f=false that's exactly what I'm talking about lol
Answer: Apriority maps to proactivity or "spontaneity" (an older use of the term) of knowledge, whereas experience is reactive/passive, something that happens to us. Since we are semantically autonomous, words meaning this or that is something that we do instead of something that just happens to us.
Now these definitions leave room for what you might call interactive knowledge, a strong mix of the a priori and empirical: science involves this to a great extent, but language does too, since there is a social element to a lot of meaning. We don't define words in a void, we cooperate to fix their references, there is social reactivity involved in learning meaning that others have developed for terms that we use.
"The definition of the word bachelor is unmarried man": is this actually synthetic a priori to some extent, then? For it is synthetic, whether a word is used to refer to this or that. The word could've been used to refer differently. Still, it is proactively assigned as it is, so there is that apriority to it...

Regarding a priori propositions


Why can't some Macs upgrade to Mountain Lion?

Question: This is an extension of this question. As noted by that question, Apple discontinued support for many of their older computers, notably the plastic MacBooks. What is the reasoning for leaving out this hardware? Is it due to hardware restrictions or is it just a push for owners of older hardware to upgrade?
Answer: The limitation is because Mountain Lion dropped support for 32 bit kernel and extensions. There are work arounds that work on some old computers (like the first gen Intel Mac Pro), leading me to believe it's simply an artificial limitation, much like the exclusion of Intel Core Solo support that came with Lion.
Comment: The first part of the workaround you link to is to upgrade the graphics card to one on a supported Mac, as the stock graphics cards will cause a kernel panic.  You can't upgrade the graphics card in an old Macbook, and it's doubtful that the old Intel GMA graphics driver was ever ported to 64-bit.  So the limitation is probably technical, not artificial.
Comment: (I have an Intel GMA Macbook, and the graphics were already starting to suffer from drawing bugs in Lion.  It was a great graphics chip for its day, but it was getting old, and apparently they didn't have the resources to give that driver the love it needed.)
Comment: It must be an arbitrary/artificial limitation, since they removed support for macbook's that have core 2 duo's, so...it's not a "64 bit cpu" limitation at least...
Comment: The limitation has to do with the inability for these machines' EFI to load 64-bit Kernle extensions, which was magically fixed by the MLPostFactor mod. My girlfriend's GMA Macbook is running it, and it's working great so far.


what is the relationship between the dynamical casimir effect and virtual particles?

Question: Since virtual particles are disturbances in a field, and not particles in any sense, as explained here, how is it that true photons arise from them when excited with kinetic energy via the dynamical casimir effect?
While the effect is described here, I was hoping to get an answer that touches more with the virtual particle's role in the effect, if it is of sigificance.
Answer: All interactions at the quantum dynamical level are subject to an analysis with Feynman diagrams, and the Casimir effect is not different in this case. Virtual pairs are internal lines in Feynman diagrams.
R.L.Jaffe has a arXiv paper that goes into the detail on the Casimir force and corresponding diagrams.
the abstract:

In discussions of the cosmological constant, the Casimir effect is often invoked as decisive evidence that the zero point energies of quantum fields are "real''. On the contrary, Casimir effects can be formulated and Casimir forces can be computed without reference to zero point energies. They are relativistic, quantum forces between charges and currents. The Casimir force (per unit area) between parallel plates vanishes as "alpha", the fine structure constant, goes to zero, and the standard result, which appears to be independent of "alpha", corresponds to the "alpha"--> infinity limit.

He separates the Casimir effect from the vacuum fluctuations effect.From the conclusions:

I have presented an argument that the experimental confirmat
  ion of the Casimir effect does not establish the reality of zero point fluctuations. Casimir forces can be calculated without reference to the vacuum and, like any other dynamical effect in QED, vanish as α→0. The vacuum-to-vacuum graphs (See Fig. 1) that define the zero point energy do not enter the calculation of the Casimir force, which instead only involves graphs with external lines. So the concept of zero point fluctuations is a heuristic and calculational aid in the description of the Casimir effect, but not a necessity.
Answer: Your sea of virtual photons normally come in and out of existence in pairs. But with a mirror moving relativistically, those pairs separate and hence become real photons (producing light).  This is explained in any paper on the effect, so I advise doing so for better enlightenment.


Credit Card Billing Cycle

Question: I am considering getting the QuikTrip credit card offered by First Bankcard. After the credit card application is approved, when does the billing cycle begin? I have contacted First Bankcard's Customer Service but they could not answer the question.
Comment: Does it matter when the billing cycle begins?
Comment: Business cards typically begin and end on the first and last of the month.  Consumer cards are variable and usually dependent upon when an account is opened.  Provided you did not make any charges, you can probably have that day changed if it is not to your satisfaction.
Answer: You need to ask the bank. There is no standard, and different card issuers behave in significantly different ways. Even within a specific bank, there may not be consistency from product to product, or even within a product, depending on when you opened it or other happenings:

Some banks have all their cards cycle on the same day of the month (i.e. the 1st or the 15th).
Some banks have all their cards cycle on the anniversary of it's open date (i.e. if you open it on the 8th it cycles on the 8th of every month) with rounding up or down for cards issued on the 29th - 31st.
Some banks have a set number of cycle batches, and your card is randomly assigned to one of those batches. for instance, they may have a batch that cycles on the 5th, the 15th, and the 25th of every month. New cards are randomly assigned in a way that keeps the sizes of the three batches consistent.
Some banks let you change your cycle date. Others don't.
Some banks used to use one of these methods (say, every card cycles on the 1st) but then switched to another (maybe they allow new cards to cycle on their anniversary date, but anyone with a card before the change still cycles on the 1st).
Sometimes, when a bank merges with another, the customers keep the cycle dates they had with their old bank. In other mergers, everyone from one bank is "forced" to convert to the cycle dates the other bank used.

Credit Card Billing Cycle


How to fix a socket that works and doesn't work and has a switch in the cord. It is a small one the size of a chandelier bulb.

Question: 25 watt round light bulb in a device that melts wax with fragrance in it goes off after a couple of minutes.  If I mess around with the bulb it will come on and then off again.  This fragrance melter is new and was a gift so want to fix it.  Do you all know how to fix it or buy a new small socket with a switch in the cord?  The socket is only 1 3/8 inch tall and is small like a chandelier bulb socket. Appreciate any help?
Answer: The contact in the light socket might be bent too far down.  Unplug the device, remove the lightbulb, gently bend the contact up a little.  The light should work awesomely then.
Comment: Or try a new bulb...
Answer: Following Mikes advice is a good way to go to cheaply do it - it can work for you, but it might not work for long either. Some of these components are made very cheaply and so the material is not the highest quality. What can happen is that metal tab gets oxidized over and corrodes - the bulb and the socket can have dissimilar metals. They do sell replacement sockets and sometimes the whole cord/switch and socket at hardware stores such as HD - look in the lighting section near the fans - there is usually an end display with such parts on it.


Is is any way to read all history from Google chrome history and save it in an excel sheet?

Question: I search for a way that allow me read all history data from Google Chrome history and save it in any format for example excel sheet .. but i want a way in which i make it by copy data from page and paste in a sheet and formating it .. i search for automatic way or a tool ?
Answer: Google saves the history in an sqlite3 database located in C:\Users\\AppData\Local\Google\Chrome\User Data\Default (on Windows 7).
Try installing an ODBC driver for sqlite3, you will then be able to use Data->From Other sources (in Get External Data) -> From Microsoft Query to get hold of the file and the data it contains. (I haven't actually done this, I just opened the file in the sqlite manager addin in Firefox to have a quick peek.)
Comment: that's what i want i found it in C:\Documents and Settings\%user%\Local Settings\Application Data\Google\Chrome\User Data\Default in windows server 2003 and also found this free browser http://sourceforge.net/projects/sqlitebrowser/ that can open these db


How to preserve inventory when migrating from BDS to Realms?

Question: I have been running a BDS Minecraft server in windows. I now want to move my and my friend's world to Realms. I took the level folder out of the worlds folder and put it in the minecraftWorlds folder on my iPad using iFunBox. I made a copy of the world to test with. While the world is the same, I have lost my inventory. How can I preserve my and my friend's inventories?
Answer: The "local" player inventory is separate from remote player inventories. You don't need to worry about your friends encountering this problem provided your account owns the realm as they will always be "remote" players and have their inventory match up.
I have not tested whether uploading a world file where you are a remote player to a realm owned by you would give your player the same problem or whether realms is smart enough to reconcile the inventories. An easy work-around is simply to dump your inventory into a chest, save and quit, then upload the world.
Comment: That's exactly what happened. All my friends were fine and I just gave myself back my valuable items.


What's the best way to manage multiple media servers, and file allocations between them?

Question: I have a file host website thats burning through 2gbit of bandwidth, so I need to start adding secondary media servers to store the files. What would be the best way to manage a multiple server setup, with a large amount of files? Preferably through php only.
Currently, I only have around 100Gb of files... so I could get a 2nd server, mirror all content between them, and then round robin the traffic 50/50, 33/33/33, etc. But once the total amount of files grows beyond the capacity of a single server, this wont work.
The idea that I had was to have a list of media servers stored in the DB with the amounts of free space left on each server. Once a file is uploaded, php will choose to which server the file is actually uploaded to, and spread out all the files evenly among the servers.
Was hoping to get some more input/inspiration.
Cant use any 3rd party services like Amazon. The files range from several bytes to a gigabyte.
Thanks
Answer: You could try MogileFS. It is a distributed file system. Has a good API for PHP. You can create categories and upload a file to that category. For each category you can define on how many servers it should be distributed. You can use the API to get a URL to that file on a random node.
Answer: If you are doing as much data transfer as you say, it would seem whatever it is you are doing is growing quite rapidly.
It might be worth your while to contact your hosting provider and see if they offer any sort of shared storage solutions via iscsi, nas, or other means.  Ideally the storage would not only start out large enough to store everything you have on it, but it would also be able to dynamically grow beyond your needs.  I know my hosting provider offers a solution like this.
If they do not, you might consider colocating your servers somewhere that either does offer a service like that, or would allow you install your own storage server (which could be built cheaply from off the shelf components and software like Freenas or Openfiler).
Once you have a centralized storage platform, you could then add web-servers to your hearts content and load balance them based on load, all while accessing the same central storage repository.
Not only is this the correct way to do it, it would offer you much more redundancy and expandability in the future if you endeavor continues to grow at the pace it is currently growing.
The other solutions offered using a database repository of what is stored where, would work, but it not only adds an extra layer of complexity into the fold, but an extra layer of processing between your visitors and the data they wish to access.
What if you lost a hard disk, do you lose 1/3 or 1/2 of all your data?
Should the heavy IO's of static content be on the same spindles as the rest of your operating system and application data?
Answer: Your best bet is really to get your files into some sort of storage that scales.  Storing files locally should only be done with good reason (they are sensitive, private, etc.)
Your best bet is to move your content into the cloud.  Mosso's CloudFiles or Amazon's S3 will both allow you to store an almost infinite amount of files.  All your content is then accessible through an API.  If you want, you can then use MySQL to track meta-data for easy searching, and let the service handle the actual storage of the files.
Comment: They are sensitive, and considering its using a lot of bandwidth (for which I get a deal), storing them elsewhere isnt an option.
Answer: i think your own idea is not the worst one. get a bunch of servers, and for every file store which server(s) it's on. if new files are uploaded, use most-free-space first*. every server handles it's own delivery (instead of piping through the main server).
pros:

use multiple servers for a single file. e.g. for cutekitten.jpg: filepath="server1\cutekitten.jpg;server2\cutekitten.jpg", and then choose the server depending on the server load (or randomly, or alternating, ...)
if you're careful you may be able to move around files automatically depending on the current load. so if your cute-kitten image gets reddited/slashdotted hard, move it to the server with the lowest load and update the entry.
you could do this with a cron-job. just log the downloads for the last xx minutes. try some formular like (downloads-per-minutefilesize(product of serverloads)) for weighting. pick tresholds for increasing/decreasing the number of servers those files are distributed to.
if you add a new server, it's relativley painless (just add the address to the server pool)

cons:

homebrew solutions are always risky
your load distribution algorithm must be well tested, otherwise bad things could happen (everything mirrored everywhere)
constantly moving files around for balancing adds additional server load

* or use a mixed weighting algorithm: free-space, server-load, file-popularity
disclaimer: never been in the situation myself, just guessing.
Answer: Consider HDFS, which is part of Apache's Hadoop. This will integrate with PHP, but you'll be setting up a second application. This will also solve all your points of balancing among servers and handling things when your file space usage exceeds one server's ability. It's not purely in PHP, though, but I don't think that's what you meant when you said "pure" anyway.
See http://hadoop.apache.org/core/docs/current/hdfs_design.html for the idea of it. They cover the whole idea of how it handles large files, many files, replication, etc.


How can I backup or archive my iPhone messages?

Question: I'm upgrading to iOS 8 and need to make some room on my phone. Under "Usage" (in Settings), my "Messages" is over 2 GB. I assume this refers to the Messages app, including iMessages and SMS. I don't necessarily need to keep these on my phone, but I'd like to archive these for posterity. Are there any good ways of doing this? I would prefer to be able to restore messages to my phone at will, but I don't know what options exist. I've used Phoneview before and found its import/export functionality limited.
Comment: If you want to access your iMessage history, use Baskup, an OS X application that backs up all your iMessages from your Macbook

https://peterkaminski09.github.io/baskup
Answer: To keep old messages for posterity, I would perform a backup and then rename it so that it does not get overwritten. A quick google search will give plenty of instructions.
As regards to restoring individual messages to your phone, I don't know that it's possible. There are certainly a number of non-free desktop apps for both PC/Mac to extract and view items from backups, again a google search will give you what you need.


How is 64-bit math accomplished on a 32-bit machine?

Question: If a 32-bit processor is, indeed, really only 32 bits in length, then how can math operations work on 64-bit numbers? For example:
<code>long lngTemp1 = 123456789123;
long lngTemp2 = lngTemp1 * 123;
</code>
According to MSDN, a long in C# is a signed 64-bit number: http://msdn.microsoft.com/en-us/library/ctetwysk(VS.71).aspx
How is it that a 32-bit Intel Microprocessor can execute code, like the above without getting an overflow?
Answer: They use the carry bit for add and subtract.  The assembler ops for "add with carry" and "subtract with carry" (or "borrow") can be used for arbitrary bit length extended precision addition and subtraction.
For multiply, if you only have a 32-bit result from multiply, you can break it into 16-bit value pairs and multiply and then shift and add (with carry) to get a full 64-bit result from 32-bit multiply.  Basically, doing the long-hand version (any two 16-bit multiplies fit in a 32-bit result) can be used to generate arbitrary bit-length multiplies using a more limited precision.
FWIW, the Intel 32-bit asm "mul" instruction can put a 64-bit result in EDX:EAX so you can actually do multiplies in 32-bit chunks (with 64-bit values to add) rather than 16-bit chunks (with 32-bit values to shift and add).
Answer: 32 bit instruction set of x86 can be used for 64 bit arithmetic, see  Extended Precision Multiplication.
Answer: Even 32-bit processors often came with a 64-bit floating point unit - but the data could only be bussed in 32-bits at a time.
More generally, however, 64-bit floating point could be accomplished even if the underlying processor only allows 8-bit integer operations. However, the compiler or programmer would have to insert sufficient code in order to virtualize the effect.


Why do we say that someone "practices" law or medicine?

Question: I'm wondering why we refer to providing legal or medical services as a practice of law or medicine, respectively. For example, we say that a lawyer practices law or a doctor practices medicine. This makes these fields sound like they're some special art, but what is the historical origin of the usage of the word practice in this context?
Comment: possible duplicate of ["Practise the piano" vs. "practise medicine"](http://english.stackexchange.com/questions/34696/practise-the-piano-vs-practise-medicine)
Comment: This is more about the history of this usage, rather than this usage compared to other, more common, usages.
Comment: Diagnosis really means two people not knowing
Answer: The word's earliest meaning was, in the OED's definition, 'to pursue or be engaged in (a particular occupation, profession, skill, or art)'. It is first recorded as such in 1421 and that is the meaning it continues to have when we speak of practising (BrEng spelling) law or medicine. At around the same time, it seems to have been used to mean 'to exercise oneself in a skill or art in order to acquire or maintain proficiency, especially in music', but it is not until 1542 that it is recorded as meaning 'to perform (an activity) or exercise (a skill) repeatedly or regularly in order to acquire, improve or maintain proficiency'. That is the meaning it most commonly has today.
Answer: One of the principle meanings of practice is

the continuous exercise of a profession b : a professional business; especially : one constituting an incorporeal property

This derives no doubt from earlier meanings of systematic performance of a skill or action.
The term is not limited to law and medicine. Consultancies, engineering firms, architects, and many other kinds of professionals also refer to their firms, specialties or lines of business as practices.
Answer: When there is no definitive way to do something in a particular profession, then it can be referred to as a practice.
Comment: I think this needs a little more than a single sentence. Do you have some support for this assertion?

Why do we say that someone “practices” law or medicine?


I have South Africa refugee passport. I am Eritrean. Can I travel to Greece without a visa?

Question: I need to visit Greek with a South African refugee document. Can I travel without a visa?
Answer: Using the passport of the country which you fled from is very risky, and not a good idea at all.
That's because a refugee using the passport of the country from which the refugee has fled makes a statement that they now accept the authority of the country from which they've fled. This will be seen as abandoning their claim to refugee status.
If the country that issued the refugee travel document learns of this use, it will likely cancel the refugee's travel document and the refugee's asylee status.


Why did SharePoint erase metadata from photos?

Question: At my job, our main server went down and our IT department had to migrate those files to SharePoint to allow us to access those files. My job is to archive, categorize, and organize some of those files. Once I downloaded the necessary photos, metadata was erased from them. The date created is now the date I downloaded them. I know that is not true. How do I extract the photos from SharePoint while keeping the original metadata? Thanks!
Answer: You would need to write a PowerShell script or use some kind of migration software like sharegate there is no out of the box option.
Here is one thread that should help you start Automatically move sharepoint files to local server
Answer: This is not possible. When you download a file from SharePoint the file gets a new created date. Same happens when you download & zip a set of SharePoint files. You loose the original SharePoint create and modify dates.
Using PowerShell script is an option.
Using OneDrive for Business client may also offer a solution. I would expect the local files to retain the original SharePoint modify date.
Another option is to use 3rd party apps. See list
There are apps that allow you download a set of files and capture the SharePoint modify dates into the zip. So after expanding the zip file you end up with files having the SharePoint modify date.
Note: some of the apps take this to the next level by exposing the actual create/modify dates in the photos itself. This also includes GPS coordinates, date time taken etc...


How do I stop windows from maximizing when dragged into a corner?

Question: How do I stop windows from maximizing when dragging them into a corner? I'm guessing this is a compiz feature but I'm not finding it in ccsm. I've turned off unity so it shouldn't be that. I'm running Natty.
Comment: possible duplicate of [How to keep programs from launching maximized?](http://askubuntu.com/questions/40571/how-to-keep-programs-from-launching-maximized)
Answer: To change the windows behaviour you can install and run Compiz Config Settings Manager ccsm .
sudo apt-get install compizconfig-settings-manager

Warning: ccsm can lead to unwanted effects that may be hard to overcome and may leave you without a desktop (see also this question for more background information).

Choose Grid from Window Management:

and adapt the window's grid behaviour to your needs:
Answer: It's the grid plugin in ccsm, deactivating it removes this feature. Or there are options to make it not maximise when dragging to the top but it will still fill one side of the screen when you drag it to that side.
Answer: Just disabling the grid in the Compiz manager did not solve this for me.
I also had to use gconf-editor to uncheck:
/ -> desktop -> cinnamon -> windows -> edge_tiling.
After that, windows were no longer snapping to fullscreen.


When using digital signatures, what does "capable of verification" mean?

Question: Numerous state regulations adopt the NCEES model language for the use of digital signatures.  This language says, among other things, that the signature must be "capable of verification."  It is not clear to me what this means, though I can make some guesses.  Is there any authoritative answer as to what, exactly, must be verifiable when using a digital signature to sign an engineering document?
Comment: Questions about licensure are on-topic.  I have re-opened the question and cleared out the earlier comments.
Answer: The question mentions numerous states, but I will use Washington State as a defined example.
Law
The state law interpreted guidance in Washington states this:

Digital Signature
A Digital Signature has the following properties:
A. It has a hardware or software cryptographic protection (such as a public/private key pair) that is unique to the licensee.
B. It can be independently verified by a third-party certification authority.
C. The Electronic Record to which it is attached is encrypted such that the recipient can verify that the document was uniquely signed by the licensee.
D. The Electronic Record to which it is attached is encrypted such that the recipient can verify if the document has been altered since the licensee signed it.

Implementation
I haven't seen very many variations in usage. All of the digital signature that I have seen are on Adobe PDFs. Their help goes through the details of how to actually use the signatures, but it also mentions how each part meets the law as stated above.
Certificate-based Signatures
On this page, the following is stated:

The digital ID contains a private key and a certificate with a public key and more. The private key is used to create the certificate-based signature. The certificate is a credential that is automatically applied to the signed document. The signature is verified when recipients open the document.
When you apply a certificate-based signature, Acrobat uses a hashing algorithm to generate a message digest, which it encrypts using your private key. Acrobat embeds the encrypted message digest in the PDF, certificate details, signature image, and a version of the document when it was signed.

This statement basically meets all of the items as described in the law.
Adobe has a separate page that talks about how the verification works, but that is only more background information stating that it does was is described above.
Answer
All of that above is a lot of text that basically says that the entire process works together, i.e. signing and verification are parts of the same general process. There is no one part that is verifiable; either the entire document (signature and document) are verified, or they aren't. If you think about it, there is no use to have one or the other.
As I mentioned in the beginning, I'm sure that there are other available methods/programs, but I have only ever seen the Adobe version in practice.
Comment: Washington does seem to provide a little more guidance than some states.  But I think what you're saying is that what must be verifiable is that the signature is MINE and not forged.  Otherwise there's no need for a certificate authority to get involved.  Am I understanding your answer correctly?
Comment: I would say that there is room for some disagreement, but the strict reading of "Third Party" would mean that it has to include a certificate authority (and the yearly fee that goes along with that).  On the more lenient side, the fact that *YOU* have the signing key in your possession would be the equivalent of having control of the original wet signed plans.