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  • Showing Egde Shaped Event Duration in StreamInsight using Debugger

    Whilst writing some courseware I wanted to be able to see the start and end times of Edge shaped events from within the debugger.  A quick recap on Edge events At the start of the event you do not know the end time and most probably cannot work it out or you should be using one of the other shapes. You enqueue an event (Start Edge) with the start time and payload of the event.  The end time of the event is set to infinity When you see the end edge come through, you enqueue another event (End Edge) with the previous start time and payload and restate the event’s end time.  This is the Retract Event All seems simple enough.  The problem is the debugger is a little shy about showing you what you need but you can get it to show you everything by also reading this article Here’s what I mean. Here is what the Event Debugger looks like by default when viewing 2 complete edge events.  Notice how all the end times are set to infinity   The above does not tell you for how long an event was valid.  I then add the “NewEndTime” column to the debugger output and there I can now see the duration of events.  You will see the Retract events (End Edge) have the same start time and payload as their respective start events (Start Edge)   You can follow the exact same logic when looking at Interval shape events.  They look a little different on the output adapter but using this article you can easily see what is happening.

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  • How to experience gradual improvement of knowledge while a newbie does .NET maintenance programming?

    - by amir
    I started my career as a software developer about 6 months ago. This is my first job, and I am the only developer in this company. I gained .NET knowledge by self study and also by doing some university projects. Our systems have old foundations based on an earlier version of .NET, and I'm starting to feel that I am not improving since I am a maintenance programmer here. Everything is old and my manager is not really taking any chances on gradually improving the software. What is your opinion? What should I do? I am newbie and also work hard to find my way through. There is no other developer, not even a senior one to help me here. I need your advice on my situation. And one last thing, can I get a new job with doing maintenance programming? I mean don't managers say that you do not have the experience of developing a new software from scratch? I feel redundant, what do I do?

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  • Designing spawning system

    - by Vlad
    I played this game recently http://www.kongregate.com/games/JuicyBeast/knightmare-tower and I am amazed by the way how different monsters are beign spawned. I personally developed my own shooter game and I added time based but also count based spawing system. By count based I mean when there are 5 enemies on stage stop spawning. But this is one example. My question is how are these spawning mechanism built, is there some pattern or some theory how they are built? Are there some online materials/pages where I can improve my knowledge? To sumarize, let just say we have 6 types of monsters. I start the game and kill of monsters of type 1,2 and 3 all the time. Once I pass the first ceiling, like in the game above, monster type 4 appear. ANd so on. As I progress trough the game, the same system of 6 types of monsters stay, but they become more and more resilient and dangerous. So I must also improve to be able to destroy the same monsters but now stronger. My question is simple, are there some theories built or written for developing this type of inteligent systems? Note: This is a general question, not tied up with some game or how exactly should the game work. I am capable to program my own mechanisms but I think I need some help. Thanks.

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  • How to Figure AdSense PPC with AdWords CPC of $0.05

    - by Melanie
    Often when I am using the Adwords Keyword tool I find keywords with a CPC of $0.05... I mean VERY often. Is this like base level when it comes to PPC or is this a possible error? For example, with a few keywords I have targetted with a 0.05 CPC, I often find a PPC of 0.25 or more. Obviously, this is because my content is triggering other keywords, although it is centered around a 0.05 keyword. I have found several keywords that have over 200,000 searches using the [exact] search parameter but have a CPC of $0.05. I plan on writing content to cover these keywords, but I am trying to figure the approximate value of these keywords. 0.05 leads me to believe there are no advertisers so IF someone were to advertise and use this keyword, it would cost them ~0.05. But since there is obviously no demand for these keywords and thus they aren't getting bids, other ads MUST be shown. How can I predict the value of ads with a CPC of $0.05? Strange question I know, but I'm just trying to understand this a bit more.

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  • Adaptive Case Management Modeling with CMMN by Jessica Ray

    - by JuergenKress
    A new version of Oracle BPM Suite 11.1.1.7 with Adaptive Case Management (ACM) is now available, so what will that mean for requirements gathering? BPM project requirements can be documented using Business Process Model and Notation (BPMN 2.0). For ACM, there is a new notation in the works. It is called Case Management Model and Notation (CMMN). For now, this notation isn’t included as a modeling tool in the new version of Oracle BPM Suite 11.1.1.7 with ACM, but it is possible that a modeling tool could be included in a future release. What is CMMN? CMMN is a standard intended to capture the common elements that Case Management Products use, the same way that BPMN is a standard for BPM products (such as Oracle BPM). CMMN is created by the Object Management Group (OMG) and is still in the beta version. In April 2014, OMG released the second beta version the CMMN 1.0, and the most recent version is available here. CMMN captures some of the elements that are commonly used when talking about ACM such as Cases, Milestones, and Tasks. It also introduces some elements that you may not automatically hear when talking about ACM such as Stages, Events, and Decorators. Here is a quick summary at a few (but not all) of the elements of CMMN taken from the CMMN spec. A Few CMMN Elements Read the complete article here SOA & BPM Partner Community For regular information on Oracle SOA Suite become a member in the SOA & BPM Partner Community for registration please visit www.oracle.com/goto/emea/soa (OPN account required) If you need support with your account please contact the Oracle Partner Business Center. Blog Twitter LinkedIn Facebook Wiki Technorati Tags: Jessica Ray,Avio,Adaptive Case Management,ACM,CMMN,SOA Community,Oracle SOA,Oracle BPM,Community,OPN,Jürgen Kress

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  • Calling COM from Intel Fortran?

    - by user57460
    I'm trying to get COM working from my Fortran application. I do a "COMINITIALIZE" followed by a "COMCreateObjectByProgID". Both of these appear to be successful and return a status of zero. However, when I try to use the COM object, I get "Unhandled exception at 0x00000000 in FortranProg01.exe: 0xC0000005: Access violation." I realize that this error can mean almost anything, but has anyone got some suggestions of common problems with COM that produce this problem? Here are some more details. My program code: program FortranProg01 use myolepg implicit none integer*4 comInitStatus integer:: comCreateStatus INTEGER(INT_PTR_KIND()) $OBJECT INTEGER(4) funcResult REAL(8) pkgVersion call COMINITIALIZE(comInitStatus) print *, comInitStatus call COMCreateObjectByProgID('MyOlePg.MyOlePkg', $OBJECT, comCreateStatus) print *, comCreateStatus funcResult = IMyOlePkg_GetPackageVersion($OBJECT, pkgVersion) print *, funcResult call COMUNINITIALIZE() end program FortranProg01 The wizard-generated interface code: INTERFACE !property PackageVersion INTEGER(4) FUNCTION IMyOlePkg_GetPackageVersion($OBJECT, pVal) INTEGER(INT_PTR_KIND()), INTENT(IN) :: $OBJECT ! Object Pointer !DEC$ ATTRIBUTES VALUE :: $OBJECT REAL(8), INTENT(OUT) :: pVal !DEC$ ATTRIBUTES REFERENCE :: pVal !DEC$ ATTRIBUTES STDCALL :: IMyOlePkg_GetPackageVersion END FUNCTION IMyOlePkg_GetPackageVersion END INTERFACE Any help would be much appreciated! Thanks! Brad.

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  • Not getting paid for hours you've worked?

    - by Sauron
    So I was reading from a previous thread about App vs Game Development: If it was for you to chose Game Development vs Application Development, which will you chose? Which brought me to this site: EA: The Human Story A lot of it talked about developers working something like 85 hours a week, and not getting paid overtime, or anything. Just getting paid for the 40 hours. Is this normal for most software companies? I mean where I work I'm only an entry level guy but I get overtime, and anything over 40 hours is considered this. But it got me thinking "Holy crap" I could never do that. My FREE time is important to me. But is this commonplace in most software companies? Or is more a rarity to certain types (game development, etc)? Because it got me scared! Like I understand having to put some extra hours in for a project... but like 80! that's ridiculous.

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  • An Oracle's Interns Story by Samarth Varshney

    - by user769227
    I have written a short write-up about my experience at Oracle and am attaching some pics along:  I joined Oracle on 5th January 2011 as part of my internship program in BITS Pilani Goa Campus. In the short period of six months, I had the most beautiful and interesting time of my life. It was fun to work in Oracle, thanks to the whole team. I had an excellent manager, simple and sophisticated, who gave me the utmost enthusiasm to work. I gained a lot of knowledge during my internship, thanks to my colleagues. They were very helpful and motivated us (interns) in every possible way. In the initial stages of work, in which you know almost nothing, they helped me gain knowledge at a rapid speed. Thanks to the vast database of study material at the Oracle site, that I could start on with my project in a very short time.  For me, the time flew like anything and made the 6 months look like a few days. It was probably due to the team, that the work was so much fun. We had our deadlines but had full freedom as to how to work and when to work. I don't remember a single instance, in which I was working and not listening to songs. I mean it will always be a time to remember. I hope to join this company and make this time last forever.  Samarth 

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  • from MS Biology to BS Computer Science [on hold]

    - by Air Borne
    I'm Marco from Italy and I'd like to ask you a piece of advice about my career. I hold a Ms degree in Biology, I enjoyed a lot studying it and I got very good grades but I didn't know what to do with my degree in the real life. Few months ago, I began to read a book about Python programming (Introduction to Computer Science, Zelle J.) and I've great fun learning Python as a beginner, I wake up in the morning thinking about doing excersies and writing simple programs with python :) I'm also watching free lectures from MIT open courseware, and I'm feeling a certain degree of regrets for never asking myself what was computer science, since it seems to me it's a magic world. After weeks of doubts, I made a move :) I applied for a CS bachelor degree abroad, I got an interview and I'm going to start this great adventure next September. I feel incredibly excited at it, but a little bit scared too. Scared because sometimes I think I'm making a great mistake for my life restarting from a bachelor in a completely different area of study. Sometimes I hear people saying the IT market is bad, sometimes I hear other ones saying quite the opposite instead. Moreover, some colleagues of mine suggested me to try to get into Bioinformatics, instead of CS. My question is: I want to really discover if CS is for me, I mean the passion of my life. I know I'm just a beginner and I can't say nothing about it yet. What do you suggest me: CS or Bioinformatics? If I get a Bs in CS, could I get into bioinformatics without relevant experience, taking into account I have a Ms Biology degree? Any comment is appreciated, thanks in advance.

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  • Creating a backup - Rsync - Connection refused (111)

    - by pablofiumara
    I am trying to create a backup of my website for free. I just want to have a backup of my website, including not only all files and the configuration but also the databases. I mean, a full backup. If it can be done automatically, it would be better. I feel there are better ways than using the cpanel to achieve that (actually, I believe sometimes web hosters does not have any cpanel). I read the following on how to do it: Automatically mirror the entire contents and configuration of your main server to a secondary backup server on a completely separate network in a different data centre. Use RSync, FXP, cPanel voodoo, or whatever method you wish to automate syncing. That is why I installed Rsync Daemon which is an alternative to SSH for remote backups. I configured it but the test went wrong. The terminal is showing me this: pablofiumara@pablofiumara-Lenovo-G470:~$ sudo rsync [email protected]::share [sudo] password for pablofiumara: rsync: failed to connect to pablofiumara.com (50.87.147.75): Connection refused (111) rsync error: error in socket IO (code 10) at clientserver.c(122) [Receiver=3.0.9] pablofiumara@pablofiumara-Lenovo-G470:~$ sudo rsync [email protected]::share failed to connect to 50.87.147.7 (50.87.147.7): Connection refused (111) rsync error: error in socket IO (code 10) at clientserver.c(122) [Receiver=3.0.9] What should I do? Is there a better or easier way to achieve what I wish (I mentioned this in the first paragraph)?

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  • Google ranking, page crawl

    - by Nawaf Mubarak
    please don't mind me for asking this newbie question about Google ranking. I know that in order to get ranked the page has to be crawled by Google bots, I have had a page example of which I will get a better understanding of how the system works with Google. I have made a page on my website last month, it got indexed pretty quickly, then I found that it's in Google's page 15 on my keyword as a start, next day it made it to page 13, then after a week it was jumping back and forth in page 17/18 up to 20. Now a month passed by, when and it isn't listed in any position of that 'keyword' sometimes I will find it in page 30, but later I won't find it anywhere, keep happening this way these days. Even if it isn't listed in any page for my keyword if I do a search for "site:thepageadress" it will be listed which means I'm not penalized and my page is there for google to see, but it isn't in the search result for my keyword. But when I write "site:thepage_adress" and I hit "search tools" option and click on "Past day" or "past week" it isn't listed, it is only listed when I click on "Past month" which I think means that Google indexed the page, looked at it once when I published it, and never looked at it again, is this a fair statement? So two questions that comes to mind here. 1- Should Google keep looking at a page even if I haven't changed any info for it? and is this an indication for me that my page is doing fine? or is it normal that Google see's it once and thats it? 2- Why and how to fix the fact that my page keeps jumping back and forth in the ranking result for keyword, and sometimes it isn't even listed, what does that mean? Sorry for the long msg, I hope to god that somebody help me with this. Thank you!

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  • both IPV4 and IPV6 at the same time over DSL connection?

    - by namiheike
    Let me describe my situation: while I connect computer with the wire, I've got an IPV6 address automatically, there's a "Wired connection" tab in network manager, and I can access an website that support IPV6 (google,facebook,twitter...)with a hosts file, or use the proxy like google.com.sixxs.org But if I want to access the whole internet, I have to create a DSL connection with username and password that ISP gave me. BUT after I change my connection into this DSL connection, I cannot access website over IPV6, even there's the site's ipv6 address in /etc/hosts, then I realize that I lose my IPV6 connection, because the ping6 says connect: Network is unreachable. the problem is, there's no IPV6 tab or options about IPV6 in the configure of DSL connection. It feels like I can only use one connection at the same time, but the DSL doesn't support IPV6 and the wired connection doesn't support IPV4(I mean, there's no way to input the password the ISP gave me) maybe make somebody uncomfortable, but when I work in MS windows, there's no such problem, (maybe just feel like) I can access V4 and V6 at the same time. So how to solve with this? thanks a lot. I'm in 11.10 + gnome3

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  • Compute the AES-encryption key given the plaintext and its ciphertext?

    - by Null Pointers etc.
    I'm tasked with creating database tables in Oracle which contain encrypted strings (i.e., the columns are RAW). The strings are encrypted by the application (using AES, 128-bit key) and stored in Oracle, then later retrieved from Oracle and decrypted (i.e., Oracle itself never sees the unencrypted strings). I've come across this one column that will be one of two strings. I'm worried that someone will notice and presumably figure out what those two values to figure out the AES key. For example, if someone sees that the column is either Ciphertext #1 or #2: Ciphertext #1: BF,4F,8B,FE, 60,D8,33,56, 1B,F2,35,72, 49,20,DE,C6. Ciphertext #2: BC,E8,54,BD, F4,B3,36,3B, DD,70,76,45, 29,28,50,07. and knows the corresponding Plaintexts: Plaintext #1 ("Detroit"): 44,00,65,00, 74,00,72,00, 6F,00,69,00, 74,00,00,00. Plaintext #2 ("Chicago"): 43,00,68,00, 69,00,63,00, 61,00,67,00, 6F,00,00,00. can he deduce that the encryption key is "Buffalo"? 42,00,75,00, 66,00,66,00, 61,00,6C,00, 6F,00,00,00. I'm thinking that there should be only one 128-bit key that could convert Plaintext #1 to Ciphertext #1. Does this mean I should go to a 192-bit or 256-bit key instead, or find some other solution? (As an aside, here are two other ciphertexts for the same plaintexts but with a different key.) Ciphertext #1 A ("Detroit"): E4,28,29,E3, 6E,C2,64,FA, A1,F4,F4,96, FC,18,4A,C5. Ciphertext #2 A ("Chicago"): EA,87,30,F0, AC,44,5D,ED, FD,EB,A8,79, 83,59,53,B7.

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  • Reinventing the Wheel, why should I?

    - by Mercfh
    So I have this problem, it may be my OCD (i have OCD it's not severe.....but It makes me very..lets say specific about certain things, programming being one of them) or it may be the fact that I graduated college and still feel "meh" at programming. Reading This made me think "OH thats me!" but thats not really my main problem. My big problem is....anytime im using a high level language/API/etc. I always think to myself that im not really "programming". I know I know...it sounds stupid. But Like I feel like....if i can't figure out how to do it at the lowest level then Im not really "understanding" it. I do this for just about every new technology I learn. I look at the lowest level and try to understand it. Sometimes I do.....most of the time I don't, I mean i've only really been programming for 4 years (at college, if you even call it programming.....our university's program was "meh"). For instance I do a little bit of embedded programming (with the Atmel AVR 8bits/Arduino stuff). And I can't bring myself to use the C compiler, even though it's 8 million times easier than using assembly......it's stupid I know... Anyone else feel like this, I think it's just my OCD that makes me feel this way....but has anyone else ever felt like they need to go down to the lowest level of the language to even be satisfied with using it? I apologize for the very very odd question, but I think it really hinders me in getting deep seeded into a programming language and making a real application of my own. (it's silly I know)

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  • I know how to program, and how to learn how to program, but how/where do you learn how to make systems properly?

    - by Ryan
    There are many things that need to be considered when making a system, let's take for example a web based system where users log in and interact with each other, creating and editing content. Now I have to think about security, validation (I don't even think I am 100% sure what that entails), "making sure users don't step on each others feet" (term for this?), preventing errors in many cases, making sure database data doesn't become problematic through unexpected... situations? All these things I don't know how or where to learn, is there a book on this kind of stuff? Like I said there seems to be a huge difference between writing code and actually writing the right code, know what I mean? I feel like my current programming work lacks much of what I have described and I can see the problems it causes later, and then the problems are much harder to solve because data exists and people are using it. So can anyone point me to books or resources or the proper subset of programming(?) for this type of learning? PS: feel free to correct my tags, I don't know what I am talking about. Edit: I assume some of the examples I wrote apply to other types of systems too, I just don't know any other good examples because I've been mostly involved in web work.

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  • install libreoffice in Ubuntu 12.04 is impossible

    - by user1587239
    What is wrong with Ubuntu repositories? sudo apt-get install libreoffice Reading package lists... Done Building dependency tree Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation: The following packages have unmet dependencies: libreoffice : Depends: libreoffice-core (= 1:3.5.4-0ubuntu1.1) but it is not going to be installed Depends: libreoffice-writer but it is not going to be installed Depends: libreoffice-calc but it is not going to be installed Depends: libreoffice-impress but it is not going to be installed Depends: libreoffice-draw but it is not going to be installed Depends: libreoffice-math but it is not going to be installed Depends: libreoffice-base but it is not going to be installed Depends: libreoffice-filter-mobiledev but it is not going to be installed Depends: libreoffice-java-common (>= 1:3.5.4~) but it is not going to be installed Recommends: libreoffice-gnome but it is not going to be installed or libreoffice-kde but it is not going to be installed E: Unable to correct problems, you have held broken packages.

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  • What should a developer know before building a public web site?

    - by Joel Coehoorn
    What things should a programmer implementing the technical details of a web site address before making the site public? If Jeff Atwood can forget about HttpOnly cookies, sitemaps, and cross-site request forgeries all in the same site, what important thing could I be forgetting as well? I'm thinking about this from a web developer's perspective, such that someone else is creating the actual design and content for the site. So while usability and content may be more important than the platform, you the programmer have little say in that. What you do need to worry about is that your implementation of the platform is stable, performs well, is secure, and meets any other business goals (like not cost too much, take too long to build, and rank as well with Google as the content supports). Think of this from the perspective of a developer who's done some work for intranet-type applications in a fairly trusted environment, and is about to have his first shot and putting out a potentially popular site for the entire big bad world wide web. Also: I'm looking for something more specific than just a vague "web standards" response. I mean, HTML, JavaScript, and CSS over HTTP are pretty much a given, especially when I've already specified that you're a professional web developer. So going beyond that, Which standards? In what circumstances, and why? Provide a link to the standard's specification. This question is community wiki, so please feel free to edit that answer to add links to good articles that will help explain or teach each particular point. To search in only the answers from this question, use the inquestion:this option.

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  • I am having trouble booting 12.04 keyboard and little man in circle appears and then nothing

    - by Rich J.
    I have a new system (ASUS 990FX mother board, 2 western dig drives, 32 gb memory, an ASUS nvidia video card (GeForce GTX560), and an ASUS DVD Burner (24B1ST)) I am struggling to get the 12.04 cd to work. I have been able to see the little man inside a circle and a graphic of a keyboard? with an == sign between them. Is this is a clue? What does it mean? After that the mauve screen with keyboard and little man in circle goes away. I get a dark background and underline cursor... even hear some work being done reading the rom.... but nothing appears on the screen. I haven't even got to the point where the graphic card is displaying improperly... it is just not displaying anything. If any kind soul has an idea about how to proceed, I am all ears. BTW, I have posted the issue to ASUS... waiting for reply.

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  • How to hide the mouse cursor

    - by MvG
    I'm building a kiosk using Ubuntu Precise on a touch screen. Now I'm looking for the appropriate way to make the mouse cursor disappear. As people know where they are pointing, displaying an arrow under their finger is useless, and having an error where they last pointed even more so. My best bet would be some kind of cursor theme consisting only of transparent cursors. I'm a bit surprised to find no UI to switch and maybe install cursor themes the default Unity UI, but as I won't be using Unity, that's not much of a problem. It appears that the alternatives listed in update-alternatives --list x-cursor-theme all refer to .theme files, so I searched the package list for those. The resulting list does not list any likely candidates, i.e. no packages containing “invisible” or “transparent” in their name. So far, some googled result yielding a readme for “XCursor Transparent Theme” is my best bet. That would mean compiling those sources myself, perhaps putting them into my PPA. I'm also a bit sceptical about that result as said readme is dated from 2003. And I'm not sure that I'm not making things overly complicated. After all, there is quite some support in Precise for touch devices, so I don't believe I'm the first one who wants to get rid of his mouse cursor. Is there another way which doesn't involve user-compiled binary code? Is there a theme package for transparent cursors which I've overlooked? Is there some other mechanism to make the cursor disappear without changing the cursor theme? I'll be using Matchbox WM, Firefox and Java applets, so I'll be happy with any solution working under such a setup. I'm not interested in any solutions twiddling with Gnome or Compiz, as I'll not be running either.

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  • What is the aim of this email? Is this a ping/sping? [closed]

    - by mplungjan
    Hi, I received this spam in my catch-all. As a webmaster of the domain it was sent to, I am really curious what the reason for this mail is. It was sent to a non-existent user "tania" on my domain - here I used mydomain.zzz - what do the sender want to achieve? Since many mail servers have stopped backscattering, not getting a bounce would not mean anything, would it? And if this is off topic, where inb the StackExchange WOULD it be on topic? Delivered-To: [email protected] Received: (qmail 8015 invoked from network); 27 Jan 2011 02:32:47 -0000 Received: from unknown (HELO p3pismtp01-021.prod.phx3.secureserver.net) ([10.6.12.26]) (envelope-sender <[email protected]>) by smtp35.prod.mesa1.secureserver.net (qmail-1.03) with SMTP for <[email protected]>; 27 Jan 2011 02:32:47 -0000 X-IronPort-Anti-Spam-Result: At4FAAlnQE1GVjtCVGdsb2JhbACWXo4gCwEWCA0YJLwyhU8EhRc Received: from mx.dt3ls.com ([70.86.59.66]) by p3pismtp01-021.prod.phx3.secureserver.net with ESMTP; 26 Jan 2011 19:32:47 -0700 Received: from 70.86.59.66 by mx.dt3ls.com (Merak 8.9.1) with ASMTP id JXF39710 for <[email protected]>; Wed, 26 Jan 2011 17:31:10 -0500 Return-Path: [email protected] Status: Message-ID: <20110126173109.4d9d6c3f2b@1c3c> From: "Tech Support" <[email protected]> To: <[email protected]> Subject: Information, as instructed. Date: Wed, 26 Jan 2011 17:31:09 -0500 X-Priority: 3 X-Mailer: General-Mailer v.3 MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Quote: I give it to you not that you may remember time, but that you might forget it now and then for a moment and not spend all your breath trying to conquer it. Because no battle is ever won he said. They are not even fought. The field reveals to a man his own folly and despair, and victory is an illusion of philosophers and fools. William Faulkner The Sound and the Fury

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  • Of transactions and Mongo

    - by Nuri Halperin
    Originally posted on: http://geekswithblogs.net/nuri/archive/2014/05/20/of-transactions-and-mongo-again.aspxWhat's the first thing you hear about NoSQL databases? That they lose your data? That there's no transactions? No joins? No hope for "real" applications? Well, you *should* be wondering whether a certain of database is the right one for your job. But if you do so, you should be wondering that about "traditional" databases as well! In the spirit of exploration let's take a look at a common challenge: You are a bank. You have customers with accounts. Customer A wants to pay B. You want to allow that only if A can cover the amount being transferred. Let's looks at the problem without any context of any database engine in mind. What would you do? How would you ensure that the amount transfer is done "properly"? Would you prevent a "transaction" from taking place unless A can cover the amount? There are several options: Prevent any change to A's account while the transfer is taking place. That boils down to locking. Apply the change, and allow A's balance to go below zero. Charge person A some interest on the negative balance. Not friendly, but certainly a choice. Don't do either. Options 1 and 2 are difficult to attain in the NoSQL world. Mongo won't save you headaches here either. Option 3 looks a bit harsh. But here's where this can go: ledger. See, and account doesn't need to be represented by a single row in a table of all accounts with only the current balance on it. More often than not, accounting systems use ledgers. And entries in ledgers - as it turns out – don't actually get updated. Once a ledger entry is written, it is not removed or altered. A transaction is represented by an entry in the ledger stating and amount withdrawn from A's account and an entry in the ledger stating an addition of said amount to B's account. For sake of space-saving, that entry in the ledger can happen using one entry. Think {Timestamp, FromAccountId, ToAccountId, Amount}. The implication of the original question – "how do you enforce non-negative balance rule" then boils down to: Insert entry in ledger Run validation of recent entries Insert reverse entry to roll back transaction if validation failed. What is validation? Sum up the transactions that A's account has (all deposits and debits), and ensure the balance is positive. For sake of efficiency, one can roll up transactions and "close the book" on transactions with a pseudo entry stating balance as of midnight or something. This lets you avoid doing math on the fly on too many transactions. You simply run from the latest "approved balance" marker to date. But that's an optimization, and premature optimizations are the root of (some? most?) evil.. Back to some nagging questions though: "But mongo is only eventually consistent!" Well, yes, kind of. It's not actually true that Mongo has not transactions. It would be more descriptive to say that Mongo's transaction scope is a single document in a single collection. A write to a Mongo document happens completely or not at all. So although it is true that you can't update more than one documents "at the same time" under a "transaction" umbrella as an atomic update, it is NOT true that there' is no isolation. So a competition between two concurrent updates is completely coherent and the writes will be serialized. They will not scribble on the same document at the same time. In our case - in choosing a ledger approach - we're not even trying to "update" a document, we're simply adding a document to a collection. So there goes the "no transaction" issue. Now let's turn our attention to consistency. What you should know about mongo is that at any given moment, only on member of a replica set is writable. This means that the writable instance in a set of replicated instances always has "the truth". There could be a replication lag such that a reader going to one of the replicas still sees "old" state of a collection or document. But in our ledger case, things fall nicely into place: Run your validation against the writable instance. It is guaranteed to have a ledger either with (after) or without (before) the ledger entry got written. No funky states. Again, the ledger writing *adds* a document, so there's no inconsistent document state to be had either way. Next, we might worry about data loss. Here, mongo offers several write-concerns. Write-concern in Mongo is a mode that marshals how uptight you want the db engine to be about actually persisting a document write to disk before it reports to the application that it is "done". The most volatile, is to say you don't care. In that case, mongo would just accept your write command and say back "thanks" with no guarantee of persistence. If the server loses power at the wrong moment, it may have said "ok" but actually no written the data to disk. That's kind of bad. Don't do that with data you care about. It may be good for votes on a pole regarding how cute a furry animal is, but not so good for business. There are several other write-concerns varying from flushing the write to the disk of the writable instance, flushing to disk on several members of the replica set, a majority of the replica set or all of the members of a replica set. The former choice is the quickest, as no network coordination is required besides the main writable instance. The others impose extra network and time cost. Depending on your tolerance for latency and read-lag, you will face a choice of what works for you. It's really important to understand that no data loss occurs once a document is flushed to an instance. The record is on disk at that point. From that point on, backup strategies and disaster recovery are your worry, not loss of power to the writable machine. This scenario is not different from a relational database at that point. Where does this leave us? Oh, yes. Eventual consistency. By now, we ensured that the "source of truth" instance has the correct data, persisted and coherent. But because of lag, the app may have gone to the writable instance, performed the update and then gone to a replica and looked at the ledger there before the transaction replicated. Here are 2 options to deal with this. Similar to write concerns, mongo support read preferences. An app may choose to read only from the writable instance. This is not an awesome choice to make for every ready, because it just burdens the one instance, and doesn't make use of the other read-only servers. But this choice can be made on a query by query basis. So for the app that our person A is using, we can have person A issue the transfer command to B, and then if that same app is going to immediately as "are we there yet?" we'll query that same writable instance. But B and anyone else in the world can just chill and read from the read-only instance. They have no basis to expect that the ledger has just been written to. So as far as they know, the transaction hasn't happened until they see it appear later. We can further relax the demand by creating application UI that reacts to a write command with "thank you, we will post it shortly" instead of "thank you, we just did everything and here's the new balance". This is a very powerful thing. UI design for highly scalable systems can't insist that the all databases be locked just to paint an "all done" on screen. People understand. They were trained by many online businesses already that your placing of an order does not mean that your product is already outside your door waiting (yes, I know, large retailers are working on it... but were' not there yet). The second thing we can do, is add some artificial delay to a transaction's visibility on the ledger. The way that works is simply adding some logic such that the query against the ledger never nets a transaction for customers newer than say 15 minutes and who's validation flag is not set. This buys us time 2 ways: Replication can catch up to all instances by then, and validation rules can run and determine if this transaction should be "negated" with a compensating transaction. In case we do need to "roll back" the transaction, the backend system can place the timestamp of the compensating transaction at the exact same time or 1ms after the original one. Effectively, once A or B visits their ledger, both transactions would be visible and the overall balance "as of now" would reflect no change.  The 2 transactions (attempted/ reverted) would be visible , since we do actually account for the attempt. Hold on a second. There's a hole in the story: what if several transfers from A to some accounts are registered, and 2 independent validators attempt to compute the balance concurrently? Is there a chance that both would conclude non-sufficient-funds even though rolling back transaction 100 would free up enough for transaction 117 (some random later transaction)? Yes. there is that chance. But the integrity of the business rule is not compromised, since the prime rule is don't dispense money you don't have. To minimize or eliminate this scenario, we can also assign a single validation process per origin account. This may seem non-scalable, but it can easily be done as a "sharded" distribution. Say we have 11 validation threads (or processing nodes etc.). We divide the account number space such that each validator is exclusively responsible for a certain range of account numbers. Sounds cunningly similar to Mongo's sharding strategy, doesn't it? Each validator then works in isolation. More capacity needed? Chop the account space into more chunks. So where  are we now with the nagging questions? "No joins": Huh? What are those for? "No transactions": You mean no cross-collection and no cross-document transactions? Granted - but don't always need them either. "No hope for real applications": well... There are more issues and edge cases to slog through, I'm sure. But hopefully this gives you some ideas of how to solve common problems without distributed locking and relational databases. But then again, you can choose relational databases if they suit your problem.

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  • A new clients come into my web agency. How to configure email and social accounts to work better? [on hold]

    - by Marco Panichi
    I created websites for many years but still have not found the right way to organize all the email and social accounts of every clients. I mean, every web agency follows dozens of customers. Each client needs at least Google Analytics, AdWords, a Facebook page, a Twitter profile, a Youtube channel, probably a listing on Google Places and maybe a Mail Chimp (or similar) account. The web agency, in my opinion, must own these accounts, use them to deliver results to the customer and -of course- make them available to the customer for two reasons: - The customer must be able to see how things are going - The client must have the ability to change web agency without suffering The web agency, however, has many problems in having all of these accounts. For example, I like the idea of having a Gmail account for each client and from that account use all the products of Google. But is not possible to create more than many Gmail account from the same ip address and with the same phone number. The web agency could invite the customer to create his own accounts but: - This is not necessary a value for the customer (indeed...) - The web agency would manage them, however, from the same ip address, incurring in problems - If phone verification occurs, the web agency has to disturb the customer for verification Have you the same problem? How to solve it?

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  • Verfication vs validation again, does testing belong to verification? If so, which?

    - by user970696
    I have asked before and created a lot of controversy so I tried to collect some data and ask similar question again. E.g. V&V where all testing is only validation: http://www.buzzle.com/editorials/4-5-2005-68117.asp According to ISO 12207, testing is done in validation: •Prepare Test Requirements,Cases and Specifications •Conduct the Tests In verification, it mentiones. The code implements proper event sequence, consistent interfaces, correct data and control flow, completeness, appropriate allocation timing and sizing budgets, and error definition, isolation, and recovery. and The software components and units of each software item have been completely and correctly integrated into the software item Not sure how to verify without testing but it is not there as a technique. From IEEE: Verification: The process of evaluating software to determine whether the products of a given development phase satisfy the conditions imposed at the start of that phase. [IEEE-STD-610]. Validation: The process of evaluating software during or at the end of the development process to determine whether it satisfies specified requirements. [IEEE-STD-610] At the end of development phase? That would mean UAT.. So the question is, what testing (unit, integration, system, uat) will be considered verification or validation? I do not understand why some say dynamic verification is testing, while others that only validation. An example: I am testing an application. System requirements say there are two fields with max. lenght of 64 characters and Save button. Use case say: User will fill in first and last name and save. When checking the fields and Save button presence, I would say its verification. When I follow the use case, its validation. So its both together, done on the system as a whole.

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  • Is using the student version of 3DS Max and Unity3d legal?

    - by SubZeron
    I am developing an indie game together with my friend using Unity3D engine. I bought "Silo 3D" for modeling two month ago and for texturing I use 3D coat. We plan to sell our game in the future. For the animations I work with 3DS max (only animation part). My question is, can I work with a students license? The license for the original version is too expensive for me. I am still at the university and I can not buy the 3DS Max license which costs 4000 €. As an alternative I have the choice beetween Blender (can´t work with this software and don't have time to invest for learning a new program) and Truespace (can´t export fbx animation and specially with bones) so for me, 3DS Max is the best choice to be effective and quick. Is it possible to prove it when I export my fbx characters from 3DS Max to Unity3D? I mean can they find out that I have used the students license of 3DS Max for the animations after the release of the game? Maybe with help of DRM? Can I solve that problem when I export the fbx from 3DS Max to Blender and after that export the same fbx to Unity3D?

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  • ROI in choosing a CMS solution

    - by Tio
    At the company I work for we need a CMS. The question is, what to choose, for me I think the best solution is to develop one of our own, but we ( my boss and I ), talked about using Drupal. But my boss is completely non-technical, and want's to take a lot of shortcut's which for programming is utterly bad. Too many shortcut's ( and that's why just last Friday we had a bug on one of our systems that caused a lot of panic ). So I'm trying to investigate on the ROI of using already existing CMS solutions VS developing our own customized CMS ( based on a open source library or not ). So that I can sell this to my boss. I'm almost sure that developing a customized CMS is the best for our small company. After a search on google I found this: Choose between a commercial, open source, or customized CMS, but the link is from 2003, it has some truth's, but the world changed a lot from 2003. But I can't seem to find anything else about it. I've developed my own CMS, so I know it's not the most easy thing to do, and that it takes time. Can someone give me any tips? EDIT: With CMS I mean Content Management System, to manage the webpages of our clients.

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