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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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• Reading OpenDocument spreadsheets using C#

  - by DigiMortal

  Excel with its file formats is not the only spreadsheet application that is widely used. There are also users on Linux and Macs and often they are using OpenOffice and other open-source office packages that use ODF instead of OpenXML. In this post I will show you how to read Open Document spreadsheet in C#. Importer as example My previous post about importers showed you how to build flexible importers support to your web application. This post introduces you practical example of one of my importers. Of course, sensitive code is omitted. We start with ODS importer class and we add new methods as we go. public class OdsImporter : ImporterBase {     public OdsImporter()     {     }       public override string[] SupportedFileExtensions     {         get { return new[] { "ods" }; }     }       public override ImportResult Import(Stream fileStream, long companyId, short year)     {         string contentXml = GetContentXml(fileStream);           var result = new ImportResult();         var doc = XDocument.Parse(contentXml);           var rows = doc.Descendants("{urn:oasis:names:tc:opendocument:xmlns:table:1.0}table-row").Skip(1);           foreach (var row in rows)         {             ImportRow(row, companyId, year, result);         }           return result;     } } The class given here just extends base class for importers (previous post uses interface but as I already told there you move to abstract base class when writing code for real projects). Import method reads data from *.ods file, parses it (it is XML), finds all data rows and imports data. As you may see then first row is skipped. This is because the first row on my sheet is always headers row. Reading ODS file Our import method starts with getting XML from *.ods file. ODS files like OpenXml files are zipped containers that contain different files. We need content.xml as all data is kept there. To get the contents of file we use SharpZipLib library to read uploaded file as *.zip file. private static string GetContentXml(Stream fileStream) {     var contentXml = "";       using (var zipInputStream = new ZipInputStream(fileStream))     {         ZipEntry contentEntry = null;         while ((contentEntry = zipInputStream.GetNextEntry()) != null)         {             if (!contentEntry.IsFile)                 continue;             if (contentEntry.Name.ToLower() == "content.xml")                 break;         }           if (contentEntry.Name.ToLower() != "content.xml")         {             throw new Exception("Cannot find content.xml");         }           var bytesResult = new byte[] { };         var bytes = new byte[2000];         var i = 0;           while ((i = zipInputStream.Read(bytes, 0, bytes.Length)) != 0)         {             var arrayLength = bytesResult.Length;             Array.Resize<byte>(ref bytesResult, arrayLength + i);             Array.Copy(bytes, 0, bytesResult, arrayLength, i);         }         contentXml = Encoding.UTF8.GetString(bytesResult);     }     return contentXml; } If here is content.xml file then we stop browsing the file. We read this file to memory and return it as UTF-8 format string. Importing rows Our last task is to import rows. We use special method for this as we have to handle some tricks here. To keep files smaller the cell count on row is not always the same. If we have more than one empty cell one after another then ODS keeps only one cell for sequential empty cells. This cell has attribute called number-columns-repeated and it’s value is set to the number of sequential empty cells. This is why we use two indexers for cells collection. private void ImportRow(XElement row, ImportResult result) {     var cells = (from c in row.Descendants()                 where c.Name == "{urn:oasis:names:tc:opendocument:xmlns:table:1.0}table-cell"                 select c).ToList();       var dto = new DataDto();       var count = cells.Count;     var j = -1;       for (var i = 0; i < count; i++)     {         j++;         var cell = cells[i];         var attr = cell.Attribute("{urn:oasis:names:tc:opendocument:xmlns:table:1.0}number-columns-repeated");         if (attr != null)         {             var numToSkip = 0;             if (int.TryParse(attr.Value, out numToSkip))             {                 j += numToSkip - 1;             }         }           if (i > 30) break;         if (j == 0)         {             dto.SomeProperty = cells[i].Value;         }         if (j == 1)         {             dto.SomeOtherProperty = cells[i].Value;         }         // some more data reading     }       // save data } You can define your own class for import results and add there all problems found during data import. Your application gets the results and shows them to user. Conclusion Reading ODS files may seem to complex task but actually it is very easy if we need only data from those documents. We can use some zip-library to get the content file and then parse it to XML. It is not hard to go through the XML but there are some optimization tricks we have to know. The code here is safe to use in web applications as it is not using any API-s that may have special needs to server and infrastructure.

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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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• 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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• Good practice or service for monitoring unhandled application errors for a small organization

  - by palto

  I'm working with multiple software with varying ways of monitoring for errors. When I make software, I usually send email with the stack trace to admins(usually me). Some customer software is monitored by a team who check that a particular batch run was successfull. Other software might not have any monitoring at all(someone will call when things go wrong horribly). Sending emails is good, except when things start going wrong, my mail gets filled fast. Also I don't want to solve the same problem in code for every software. Is there some relatively cheap and low maintenance software or practice to handle this. I want it to be cheap/low maintenance because usually I work alone or in teams of 5 or smaller. For example it would be great if errors would be aggregated so I don't get 10 000 emails when something unexpected happens... For clarification: By unhandled errors I mean Exceptions that were unhandled by application code that were propagated to Tomcat or Jboss. I don't need help with how to catch those errors. I need help with what to do with them. Is there any cloud application that I could send my errors to? Or some simple server to install? Or some library that can handle errors using configuration files. I use Java if that is any help.

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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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• What is meant by, "A user shouldn't decide whether it is an Admin or not. The Privileges or Security system should."

  - by GlenPeterson

  The example used in the question pass bare minimum data to a function touches on the best way to determine whether the user is an administrator or not. One common answer was: user.isAdmin() This prompted a comment which was repeated several times and up-voted many times: A user shouldn't decide whether it is an Admin or not. The Privileges or Security system should. Something being tightly coupled to a class doesn't mean it is a good idea to make it part of that class. I replied, The user isn't deciding anything. The User object/table stores data about each user. Actual users don't get to change everything about themselves. But this was not productive. Clearly there is an underlying difference of perspective which is making communication difficult. Can someone explain to me why user.isAdmin() is bad, and paint a brief sketch of what it looks like done "right"? Really, I fail to see the advantage of separating security from the system that it protects. Any security text will say that security needs to be designed into a system from the beginning and considered at every stage of development, deployment, maintenance, and even end-of-life. It is not something that can be bolted on the side. But 17 up-votes so far on this comment says that I'm missing something important.

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• Invalid Html Response and JS Errors when you open your Application in Visual Studio 2013

  - by imran_ku07

   I was working on an application which uses Telerik controls. The application was working fine for a while. Suddenly, the application stopped working. I mean lot of my application pages becoming very very ugly. I found JavaScript errors on every Browser's console. When I check the page view-source, the generated HTML was messy and invalid. This was only happening with my local machine. If someone else on my network accesses my application pages, he will get the correct HTML and no JavaScript errors. My mind was blowing because the same page was generating invalid HTML(and JavaScript errors) when I access the page using a local browser but generate correct HTML(and no JavaScript errors) when someone else access my application page remotely. Then I realized that I the only change I made last was opening my application in Visual Studio 2013 RTM which I installed few days ago. I closed the Visual Studio 2013, everything work like a charm. Then I became100% sure that this is only happening due to new Visual Studio 2013 feature called Browser Link. I just open the application again and add this in web.config. Everything become fine Happy coding :)   <add key="vs:EnableBrowserLink" value="false" />

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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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• 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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• 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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• 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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• 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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• Using Behavior Trees and Events together

  - by weichsem

  I am beginning to work with behavior trees and am unsure how events should be handled within the tree. Lets say we have a space game where the player is dogfighting with a handful of other ships, some friendly some not. The player destroys a ship and the rest of the hostile ships should then start to retreat. How was should the shipWasDestroyed event effect the other ship's behavior trees so that they start running the retreat behavior? One way I could think of doing this is have all the conditions I care about be high level nodes that effectively state change the ship. This would mean I'd have to check all of these state change conditions on every frame the behavior tree was run, even if they are very rare occurrences. I'd prefer not doing this for performance and complexity reasons. From looking at the Halo papers on behavior trees it seems that they handled this by dynamically placing nodes into the tree when the event occurred. It seems like calculating where the new node should go could be problematic depending on the current state of the running behavior. How is this normally handled?

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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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• CQRS applicability when some commands need to block the UI

  - by regularfry

  I am working on an app which I would dearly love to transition from a fairly traditional layered architecture to CQRS, for a number of reasons, not least fo which is that having a robust event log will make adding a couple of feature requests I can see barrelling towards me trivial to accomodate. Now, I have a conceptual problem: of around 40 commands the user can initiate, there are three which the user needs to be sure have successfully completed before the UI lets them do anything else. Everything else fits into the "submit a request, query for success later" model, except for these three commands. How is this handled in CQRS-land? Do I separate the three blocking commands to effectively a third service, so I have Commands, Queries, and BlockingCommands? Do I have a two-stage event processor with an in-request blocking first stage which only gets used for the blocking commands? Does the existence of these three commands mean that the whole idea of applying CQRS is invalid? Should I just pretend they aren't blocking and poll for success in the UI? I'm sure this must come up on other projects, how is it usually handled?

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• Complexity of defense AI

  - by Fredrik Johansson

  I have a non-released game, and currently it's only possible to play with another human being. As the game rules are made up by me, I think it would be great if new players could learn basic game play by playing against an AI opponent. I mean it's not like Tennis, where the majority knows at least the fundamental rules. On the other hand, I'm a bit concerned that this AI implementation can be quite complex. I hope you can help me with an complexity estimation. I've tried to summarize the gameplay below. Is this defense AI very hard to do? Basic Defense Game Play Player Defender can move within his land, i.e. inside a random, non-convex, polygon. This land will also contain obstacles modeled as polygons, that Defender has to move around. Player Attacker has also a land, modeled as another such polygon. Assume that Defender shall defend against Attacker. Attacker will then throw a thingy towards Defender's land. To be rewarded, Attacker wants to hit Defender's land, and Defender will want to strike away the thingy from his land before it stops to prevent Attacker from scoring. To feint Defender, Attacker might run around within his land before the throw, and based on these attacker movements Defender shall then continuously move to the best defense position within his land.

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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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• How to fix "Disk drive for /boot/efi is not ready or not present"?

  - by N.N.

  After I updated BIOS/UEFI version to 1101 on an Asus P8Z68-V PRO motherboard Ubuntu (11.10) did not boot. After POST all I saw was a black screen with a blinking cursor in the top left corner. I booted an Ubuntu 11.10 live-CD and set the flag for the 20 MB partition before my boot partition to "bios_grub". Then I was able to boot and login. But now every time I boot and Ubuntu loads I get the following message: Disk drive for /boot/efi is not ready or not present. Continue waiting or press s to skip or m for manual recovery. I am able to login if I choose to ignore it by pressing s, but what does this message mean? How can I fix what the message warns about? After logging in I have noticed that /boot/efi is empty. The following forum post speaks of the same issue ubuntuforums.org/showthread.php?t=1893030. Updating to the latest BIOS/UEFI - version 3203, did not have any effect on this issue.

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• What's the best way to learn/increase problem-solving skills?

  - by tucaz

  Hi all! I'm not sure this is the right place to ask this question, neither if this is the right way to ask this question but I hope you help me if it is not. I work as a programmer since I was 15 (will be 24 next week) so learning programming logic was somehow natural during the course of my career and I think that it helped me to get pretty good problem-solving. One thing none of us (programmers) can deny is that programming logic helps us in a lot of fields outside computer programming. So I'd say it is a very valuable resource that one should learn. My girlfriend is not a programmer and graduated in college on a non related course (Foreign Relations) because she didn't know what to study back then. As the years passed she discovered that she liked Logistics and started to work with it almost two years ago. However, since she does not have a technical background (not even basic Math) she is really having a hard time with it. She is already trying to catch up with Math, but even simple questions/brain-teasers are hard to her. For example, trying to find the missing numbers of this sequence: 0, 1, 1, 2, 3, 5, 8, _, _, 34 and so on. We know that this is Fibonacci but if we didn't we would probably be able to get to the correct answer just by "guessing" (using our acquired problem-solving skills). I'm not sure if problem-solving skills or logic are the correct name for it, but this is what I mean: quick solve problems, brain-teasers, find patterns, have a "sharp" mind. So, the question is: what is the best way for someone to learn this kind of skills without being a programmer (or studying algorithms and such)? If you say it is a book, could you please recommend one? Thanks a lot!

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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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• What is the `ServerName` attribute for apache2 and what does it do?

  - by freddydoggie

  I do not know what this config setting means. Does it mean that it registers a domain name? Is it like DNS? Here is what I have for my apache2 default config ServerName staugie.org ServerAdmin webmaster@localhost DocumentRoot /var/www <Directory /> Options FollowSymLinks Indexes MultiViews AllowOverride All </Directory> <Directory /var/www/> Options Indexes FollowSymLinks MultiViews AllowOverride All Order allow,deny allow from all </Directory> ScriptAlias /cgi-bin/ /usr/lib/cgi-bin/ <Directory "/usr/lib/cgi-bin"> AllowOverride All Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch Order allow,deny Allow from all </Directory> ErrorLog ${APACHE_LOG_DIR}/error.log # Possible values include: debug, info, notice, warn, error, crit, # alert, emerg. LogLevel warn CustomLog ${APACHE_LOG_DIR}/access.log combined Alias /doc/ "/usr/share/doc/" <Directory "/usr/share/doc/"> Options Indexes MultiViews FollowSymLinks AllowOverride None Order deny,allow Deny from all Allow from 127.0.0.0/255.0.0.0 ::1/128 </Directory> also, is there any way to register a free domain through the apache foundation?

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• Contract Work - Lessons Learned

  - by samerpaul

  I thought I would write a post of a different nature today, but still relevant to the tech world. I do a lot of contract jobs myself and really enjoy it. It's nice to keep jumping from project to project, and not having to go to an office or keep regular hours, etc. I really enjoy it. I have learned a lot in the past few years of doing it (both from experience and from help given to me from others, and the internet) so I thought I'd share some of that knowledge/experience today.So here's my own personal "lesson's learned" that hopefully will help you if you find yourself doing contract work:Should I take the job?Ok, so this is the first step. Assuming you were given sufficient information about what they want, then you should really think about what you're capable of doing and whether or not you should take this job. Personally, my rule is, if I know it's possible, I'll say yes, even if I don't yet know how to do it. That's because the internet is such a great help, it would be rare to run into an issue that you can't figure out with some help. So if your clients are asking for something that you don't yet know how to program, but you know you can do it on the platform then go for it. How else are you going to learn?Use this rule with some limitation, however. If you're really lacking the expertise or foundation in something, then unless you have tons of time to complete the project, then I wouldn't say yes. For example, I haven't personally done any 3d/openGL programming yet so I wouldn't say yes to a project that extensively uses it. OK, so I want the job, but how much do I charge?This part can be tricky. There is no set formula really, but I have some tips for pricing that will hopefully give you a better idea on how to confidently ask your price and have them accept. Here are some personal guidelinesHow much time do you have to complete the project? If it's shorter than average, then charge more. You can even make a subtle note about this (or not so subtle if they still don't get it.) If it seems too short of a time (i.e. near impossible to complete), be sure to say that. It looks bad to promise a time that you can't keep--and it makes it less likely for them to return to you for work.Your Hourly rate: How long have you been working in that language? Do you have existing projects to back you up? Or previous contacts that can vouch for your work? Are there very few people with your particular skill set? All of these things will lend themselves to setting an hourly rate. I'd also try out a quick google search of what your line of work is, to see what the industry standard is at that point in time.I wouldn't price too low, because you want to make your time worth it. You also want them to feel like they're paying for quality work (assuming you can deliver it :) ). Finally, think about your client. If it's a small business, then don't price it too high if you want the job. If it's an enterprise (like a Fortune company), then don't be afraid to price higher. They have the budget for it.Fixed price: If they want a fixed price project, then you need to think about how many hours it will take you to complete it and multiply it by the hourly rate you set for yourself. Then, honestly, I would add 10-20% on top of that. Why? Because nothing ever works exactly how you want it to. There are lots of times that something "trivial" is way harder than it should be, or something that "should work" doesn't for hours and it eats away at your hourly rate. I can't count the number of times I encountered a logical bug that took away an entire's day work because debuggers don't help in those cases. By adding that padding in, it's still OK to have those days where you don't get as much done as you want. And another useful tip: Depending on your client, and the scope, you most likely want to set that you both sign off on a specification sheet before doing any work, and that any changes will result in a re-evaulation of the price. This is to help protect you from being handed a huge new addition to the project half-way in, without any extra payment.Scope of project: Finally, is it a huge project? Is it really small/fast? This affects how much your client will be willing to pay. If it sounds big, they will be willing to pay more for it. If it seems really small, then you won't be able to get away with a large asking price (as easily).Ok, I priced it, now what?So now that you have the price, you want to make sure it feels justified to your client. I never set a price before I can really think about everything. For example, if you're still in your introduction phase, and they want a price, don't give one! Just comment that you will send them a proposal sheet with all the features outlined, and a price for everything. You don't want to shout out a low number and then deliver something that is way higher. You also don't want to shock them with a big number before they feel like they are getting a great product.Make up a proposal document in a word editor. Personally, I leave the price till the very end. Why? Because by the time they reach the end, you've already discussed all the great features you plan to implement, and how it's the best product they'll ever use, etc etc...so your price comes off as a steal! If you hit them up front with a price, they will read through the document with a negative bias. Think about those commercials on TV. They always go on about their product, then at the end, ask "What would you pay for something like this? $100? $50? How about $20!!". This is not by accident.Scenario: I finished the job way earlier than expectedYou have two options then. You can either polish the hell out of the application, and even throw in a few bonus features (assuming they are in-line with the customer's needs) or you can sit and wait on it until you near your deadline. Why don't you want to turn it in too early? Because you should treat that extra time as a surplus. If you said it is going to take you 3 weeks, and it took you only 1, you have a surplus of 2 weeks. I personally don't want to let them know that I can do a 3 week project in 1 week. Why not? Because that may not always be the case! I may later have a 3 week project that takes all 3 weeks, but if I set a precedent of delivering super early, then the pressure is on for that longer project. It also makes it harder to quote longer times if you keep delivering too early.Feel free to deliver early, but again, don't do it too early. They may also wonder why they paid you for 3 weeks of work if you're done in 1. They may further wonder if the product sucks, or what is wrong with it, if it's done so early, etc.I would just polish the application. Everyone loves polish in their applications. The smallest details are what make an application go from "functional" to "fantastic". And since you are still delivering on time, then they are still going to be very happy with you.Scenario: It's taking way too long to finish this, and the deadline is nearing/here!So this is not a fun scenario to be in, but it'll happen. Sometimes the scope of the project gets out of hand. The best policy here is OPENNESS/HONESTY. Tell them that the project is taking longer than expected, and give a reasonable time for when you think you'll have it done. I typically explain it in a way that makes it sound like it isn't something that I did wrong, but it's just something about the nature of the project. This really goes for any scenario, to be honest. Just continue to stay open and communicative about your progress. This doesn't mean that you should email them every five minutes (unless they want you to), but it does mean that maybe every few days or once a week, give them an update on where you're at, and what's next. They'll be happy to know they are paying for progress, and it'll make it easier to ask for an extension when something goes wrong, because they know that you've been working on it all along.Final tips and thoughts:In general, contract work is really fun and rewarding. It's nice to learn new things all the time, as mandated by the project ,and to challenge yourself to do things you may not have done before. The key is to build a great relationship with your clients for future work, and for recommendations. I am always very honest with them and I never promise something I can't deliver. Again, under promise, over deliver!I hope this has proved helpful!Cheers,samerpaul

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• How to explain a layperson why a developer should not be interrupted while neck-deep in coding?

  - by András Szepesházi

  If you just consider the second part of my question, "Why a developer should not be interrupted while neck-deep in coding", that has been discussed a number of times by smart people. Heck, even the co-founder of SO, Joel Spolsky, wrote a blog post about "getting in the zone" and "being knocked out of the zone" and why it takes an average of 15 minutes to achieve productivity when participating in complex, software development related tasks. So I think the why has been established. What I'm interested in is how to explain all that to somebody who doesn't know beans about Beans (khmm I mean software development). How to tell the wife, or the funny guy from accounting at the workplace, or the long time friend who pings you on Skype every 30 minutes with a "Wazzzzzzup?!", that all the interruptions have a much deeper impact on your work than the obvious 30 seconds they took from your time. Obviously you can't explain it by sentences like "I have to juggle a lot of variable names in my short term memory" unless you want to be the target of blank stares or friendly abuse. I'd like to be able to explain all that to non-developers in a way that will make them clearly understand - without being offensive, elitist or too technical. EDIT: Thanks to everyone for their great insights. I've accepted EpsilonVector's answer as his analogy was the closest one to my original needs. The "falling asleep" explanation is neither offensive nor technical, almost anyone can relate to it, and the consequences of getting disturbed while falling asleep or while being in the zone are very similar: you experience frustration and you "lose" 15-20 minutes of time.

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• Turn-based Client-Server Card Game - Unicast (TCP) or Multicast (UDP)

  - by LDM91

  I am currently planning to make a card game project where the clients will communicate with the server in a turn-based and synchronous manner using messages sent over sockets. The problem I have is how to handle the following scenario: (Client takes it turn and sends its action to server) Client sends a message telling the server its move for the turn (e.g. plays the card 5 from its hand which needs to placed onto the table) Server receives messages and updates game state (server will hold all game state). Server iterates through a list of connected clients and sends a message to tell of them change in state Clients all refresh to display the state This is all based on using TCP, and looking at it now it seems a bit like the Observer pattern. The reason this seems to be an issue to me is this message doesn't seem to be point-to-point like the others as I want to send it to all the clients, and doesn't seem very efficient sending the same message in that way. I was thinking about using multicasting with UDP as then I could send the message to all the clients, however wouldn't this mean that the clients would in theory be able to message each other? There is of course the synchronous aspect as well, though this could be put on top of the UDP I guess. Basically, I would like to know what would be good practice as this project is really all about learning, and even though it won't be big enough to encounter performance issues from this I would like to consider them anyway. However, please note I am not interested in using message oriented middleware as a solution (I have experience with using MOM and I'm interested in considering other options excluding MOM if TCP sockets is a bad idea!).

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