I have a short question. Why XML files should be validated and not just well-formed?  I looked at several places for an answer to this question but I have not found a good one.
I wasn't aware of a difference, but a coworker says there is, although he can't back it up. What's the difference if any?
Ssh login hook? What is the maximum number of Locations Discovered that one can achieve in Skyrim? Fraleigh(7ed) Theorem33.12. Let $p$ be a prime and let $n\in\mathbb{Z}^+$. If $E$ and $E&#39;$ are fields of order $p^n$, then $E \simeq E&#39;$.   Proof in the text: Both $E$ and $E&#39;$ have $\mathbb{Z}_p$ as prime field, up to isomorphism. By Corollary 33.6(A finite extension $E$ of a finite field $F$ is a simple extension of $F$), $E$ is a simple extension of $\mathbb{Z}_p$ of degree $n$, so there exists an irreducible polynomial $f(x)$ of degree $n$ in $\mathbb{Z}_p[x]$ such that $E\simeq \mathbb{Z}_p[x]/ \langle f(x) \rangle$. Because the elements of $E$ are zeros of $x^{p^n}-x$, *we see that $f(x)$ is a factor of $x^{p^n}-x$ in $\mathbb{Z}_p[x]$*. Because $E&#39;$ also consists of zeros of  $x^{p^n}-x$, we see that $E&#39;$ also contains zeros of irreducible $f(x)$ in $\mathbb{Z}_p[x]$. Thus, because $E&#39;$ also contains exactly $p^n$ elements, $E&#39;$ is also isomorphic to $E\simeq \mathbb{Z}_p[x]/\langle f(x) \rangle$.  I don't know why $f(x)$ divides $x^{p^n}-x$. $E$ has a zero $\alpha$ of $f(x)$, but it doesn't need to have all the zeros of $f(x)$. So $f(x)=(x-\alpha)g(x)$ in $E[x]$ and $g(x)$ need not be splitted into linear factors. How can $f(x)$ divide $x^{p^n}-x$? How do I figure out what package something is in without resorting to Google? I often find myself wanting to install something, but I'm unsure of what package it's in. This is a very common occurrence for me:  $ make html sphinx-build -b djangohtml -d _build/doctrees   . _build/html make: sphinx-build: Command not found make: *** [html] Error 127  $ sudo apt-get install sphinx E: Unable to locate package sphinx  $ sudo apt-get install sphinx-build E: Unable to locate package sphinx-build   googles  $ sudo apt-get install python-sphinx   Is there a better way? Multiple object instances represented by two slightly shifted rectangles In a software diagram, I'd like to be able to represent multiple instances of an object by two rectangles with one of them slightly shifted. I recently learned about the pic style so I'm using it with two nodes to achieve what I want.  The following example does work, but I'd like to know if I can do the same without using the fill=white. My hack kind of assumes the entire picture background is white and that may not always hold. I'd like to be able to crop the unwanted picture part out.  \documentclass[crop,border=3pt]{standalone}  \usepackage{pgf,tikz} \usetikzlibrary{positioning}  \begin{document} \begin{tikzpicture}[     every node/.style={font=\sffamily\small},     block/.style={         rectangle, draw, align=center, minimum width=2cm,         minimum height=1.4cm, font=\sffamily\small     },     multinode/.pic={         \node [block] at (0.1,0.1) {};         \node [block, \tikzpictextoptions, fill=white] at (0,0) {\tikzpictext};% &lt;-- FILL WHITE     } ]     \node [block] (STG) at (2,5) {single\\instance};     \pic [pic text={multi\\instance}] at (5,5) {multinode}; \end{tikzpicture} \end{document}   The following images show first one version with the fill white hack, and then one version without it. JavaScript: Bitwise shift of long long number I need to bitwise shift a value 64 times in JavaScript. But JavaScript starts rounding after 32.  For example:  for(var j = 0; j &lt; 64; j++) {     mask = mask &lt;&lt; 1;     console.log(mask); }   This prints value from 0 to 1073741824 but then rounds of and starts printing 0. Using past tense when referencing a still-true fact In the sentence: "I didn't know she had a son,"   Can I say "I didn't know she has a son" instead, because he is a teenager now?  Or are both correct? What is the significance of Lie groups $SO(3)$ and $SU(2)$ to particle physics? I was hoping someone could give an overview as to how the Lie groups $SO(3)$ and $SU(2)$ and their representations can be applied to describe particle physics?  The application of Lie groups and their representations is an enormous field, with vast implications for physics with respect to such things as unification, but I what specifically made these groups of physical importance and why there study is useful.  I have just started studying these two groups in particular, but from a mathematical perspective, I'd very much appreciate understanding some sort of physical motivation. Consider an irreducible but possibly periodic Markov chain on a finite state space with transition matrix $P$. We know there exists a unique stationary distribution $\pi$. If the Markov chain were aperiodic, we would have $P^n_{ij} \to \pi(j)$ as $n \to \infty$. This fails if the chain is periodic, but we have convergence of the Cesaro averages: $$\frac{1}{n}\sum_{k=1}^n P^k_{ij} \to \pi(j) \text{ as } n \to \infty.$$ Can anyone point me to a reference that states this fact? Every reference I've seen only considers convergence for aperiodic chains, or "fixes" periodicity by considering a lazy version of the chain. Alternatively, is there a simple way to obtain this result using the result for aperiodic chains? Seemingly random reputation gain of 1 How to transit through Delhi without a visa? How can I reorder my divs using only CSS? If the dot product between two vectors is $0$, are the two linearly independent? If we have vectors $V$ and $W$ in $\mathbb{R^n}$ and their dot product is $0$, are the two vectors linearly independent?  I can expand $V_1 \cdot V_2 = 0 \Rightarrow v_1w_1+...+v_nw_n = 0$, but I don't understand how this relates to linear independence. Is there a way to access Windows file with administrative rights using WSL?  sudo vi /mnt/c/Users/a/admin/file.txt Can't boot Ubuntu or Windows 8 after Ubuntu 64-bit install on Samsung series 7 Windows 8 laptop, error "All boot options are tried." I have a Samsung Chronos 7 laptop (NP770Z5E) pre-installed with Windows 8, and I wanted to install Ubuntu 13.04 alongside it, so I can dual boot. Here is what I've done:  Updated BIOS to lastest version (P04ABU) using Samsung Updater Reduced Win8 partition by half, I left the others untouched Created a bootable USB stick using  and a Ubuntu 13.04 64-bit image Disabled FastStartup on Win 8 Disabled Fast BIOS Mode Boot Mode changed to CSM OS  Update:  Also disabled Secure Boot (I had to disable it in order to select CSM OS)  After that I saved the BIOS settings, and shut down the computer. I plugged in the USB drive, powered the computer on, entered the BIOS and tried to change the boot order. Oddly, there was only one option in the boot order screen, the USB drive (HDD didn't show up in the boot priority screen). I ignored that and installed Ubuntu. I've created 3 partitions from the unused spaced left: a 8GB swap, a 100MB BIOS boot partition, and the rest to ext4, mounted in /. Boot loader installed on /sda. After a reboot, this message appears:  All boot options are tried. Press &lt;F4&gt; key to recover with factory image using Recovery or any other keys for next boot loop iteration.  So I went to the BIOS to change the boot device priority, and the list is empty! Enabling Secure Boot and Fast BIOS had no effect. I used the Ubuntu Live USB to check the disk contents, I can see the Ubuntu and Win 8 partitions. I've used Boot Repair (using the Recommended Repair), with no avail, the Boot Repair log is here:  Boot Repair showed me a message about the system being a&quot;EFI system&quot;. I suppose that means that I should have checked out the advanced settings. I don't know how to proceed. I don't know if it's a good idea to &quot;recover with factory image&quot; since I have modified the original partitions. Maybe I need to experiment with Boot Repair's advanced settings. I am making a fudge recipe that calls for 1cup whole milk and 5 cups sugar. It also uses 2 sticks of butter and 25 marshmallows. I'm wondering if I can omit the milk and cut back on the sugar by using sweetened condensed milk. When is the Killing form null? When is the Killing form $\kappa$ of a Lie algebra $\mathfrak g$ null, i.e. $\kappa(\cdot,\cdot)=0$? Surely this is true for any Lie algebra with trivial bracket, but is this the only case? I can't seem to find any nontrivial examples. The Lie algebra of $SL_n(\mathbb C)$ are the matrices where the trace is $0$. But what is the Lie algebra of $SL_n(\mathbb H)$ where $\mathbb H$ is the quaternions? Nth max salary in Oracle How unusual is getting a Masters degree in a slightly different field than Bachelors? Would it be out of the ordinary to get a Bachelors in Mechanical Engineering and then go for a Masters in something like Civil or Structural Engineering?  I don't know a lot about how transitioning to a Masters program works.. Do people usually continue on in the same field, or is branching out common?