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  • What alternative is better to diagram this scenario?

    - by Mosty Mostacho
    I was creating and discussing a class diagram with a partner of mine. To simplify things, I've modify the real domain we're working on and made up the following diagram: Basically, a company works on constructions that are quite different one from each other but are still constructions. Note I've added one field for each class but there should be many more. Now, I thought this was the way to go but my partner told me that if in the future new construction classes appear we would have to modify the Company class, which is correct. So the new proposed class diagram would be this: Now I've been wondering: Should the fact that in no place of the application will there be mixed lists of planes and bridges affect the design in any way? When we have to list only planes for a company, how are we supposed to distinguish them from the other elements in the list without checking for their class names? Related to the previous question, is it correct to assume that this type of diagram should be high-level and this is something it shouldn't matter at this stage but rather be thought and decided at implementation time? Any comment will be appreciated.

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  • How should we deal with multiple transaction-report requests?

    - by Mithir
    We are developing a system for the retail market which one of it's features will enable clients(actually consumer clubs) to go through all transactions made by end-clients. One of the ways to get this information will be via an API. The idea is that there will be requests for reports with a start date and an end date, and a response will have all the transactions between those dates. We are worry that some reports may be very large, and that some clients will repeatedly request for reports, in this case the DB and CPU will be very overloaded. The same server that will service those requests, also takes care the the actual retail transactions (received by proprietary devices) and a Web application. We are not sure about how to limit the report requests from the API so that it won't affect the system too much. So, how should we deal with this scenario? any thoughts? EDIT: just to make clear: When I mentioned proprietary devices I meant "On-Location" devices which are used during sales with end-clients, this means that these requests shouldn't get delayed, and this is the main concern.

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  • how should I design Objects around this business requirement?

    - by brainydexter
    This is the business requirement: " A Holiday Package (e.g. New York NY Holiday Package) can be offered in different ways based on the Origin city: From New Delhi to NY From Bombay to NY NY itself ( Land package ) (Bold implies default selection) a. and b. User can fly from either New Delhi or Bombay to NY. c. NY is a Land package, where a user can reach NY by himself and is a standalone holidayPackage. " Let's say I have a class that represents HolidayPackage, Destination (aka City). public class HolidayPackage{ Destination holidayCity; ArrayList<BaseHolidayPackageVariant> variants; BaseHolidayPackageVariant defaultVariant; } public abstract class BaseHolidayPackageVariant { private Integer variantId; private HolidayPackage holidayPackage; private String holidayPackageType; } public class LandHolidayPackageVariant extends BaseHolidayPackageVariant{ } public class FlightHolidayPackageVariant extends BaseHolidayPackageVariant{ private Destination originCity; } What data structure/objects should I design to support: options a default within those options Sidenote: A HolidayPackage can also be offered in different ways based on Hotel selections. I'd like to follow a design which I can leverage to support that use case in the future. This is the backend design I have in mind.

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  • Switching mdadm to an external bitmap

    - by Oli
    I've just read this in another post about improving RAID5/6 write speeds: After increasing stripe cache & switching to external bitmap, my speeds are 160 Mb/s writes, 260 Mb/s reads. :-D I've already found out how to increase the stripe cache and this worked pretty well but I'd like to know more about an external bitmap. I have an incredibly fast (540MB/s) RAID0 SSD that would do well if a bitmap does what I think it does but I'm still very unsure. I've only known about them as long as I've known this post. A few questions: What is a bitmap (in terms of mdadm)? What are the advantages of an internal bitmap (over external)? What are the advantages of an external bitmap (over internal)? How do I switch between the two? I should add that while this is a I'm-bored-let's-break-something thread, I do value the data stored on the RAID array. If doing this is going to put data at significant risk, please let me know.

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  • Triple buffering causes input lag?

    - by user782220
    Consider some time in between two vsyncs. Suppose the first display buffer is being used to display the current image, and suppose the game was really fast and computed and rendered the next image to the second display buffer and the next one after that to the third display buffer. That is the rendering to the second and third display buffer happens so fast that it occurs before the next vsync. Suppose input from the user comes in now. What you would like is for the results of the input to show up on the next vsync or (probably more typical) the vsync after that. However, with the third display buffer already rendered the input can only effect the image after that. Meaning the input will only take effect at best 3 vsyncs later. I wish i had an image to show the exact timings of what I mean.

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  • What are the Crappy Code Games - Who can enter?

    - by simonsabin
    This is part of a series on the Crappy Code Games The background Who can enter? What are the challenges? What are the prizes? Why should I attend? Tips on how to win Who can enter? Anyone can enter the competition, whats more anyone can just come along for the evening. All the evenings are aimed at being a social evening with food and drink. So just think of them as usergroup meetings with The evening will have lots of SQL bods in attendance and I'll be trying to help out anyone that wants some...(read more)

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  • Inheritance vs containment while extending a large legacy project

    - by Flot2011
    I have got a legacy Java project with a lot of code. The code uses MVC pattern and is well structured and well written. It also has a lot of unit tests and it is still actively maintained (bug fixing, minor features adding). Therefore I want to preserve the original structure and code style as much as possible. The new feature I am going to add is a conceptual one, so I have to make my changes all over the code. In order to minimize changes I decided not to extend existing classes but to use containment: class ExistingClass { // .... existing code // my code adding new functionality private ExistingClassExtension extension = new ExistingClassExtension(); public ExistingClassExtension getExtension() {return extension;} } ... // somewhere in code ExistingClass instance = new ExistingClass(); ... // when I need a new functionality instance.getExtension().newMethod1(); All functionality that I am adding is inside a new ExistingClassExtension class. Actually I am adding only these 2 lines to each class that needs to be extended. By doing so I also do not need to instantiate new, extended classes all over the code and I may use existing tests to make sure there is no regression. However my colleagues argue that in this situation doing so isn't a proper OOP approach, and I need to inherit from ExistingClass in order to add a new functionality. What do you think? I am aware of numerous inheritance/containment questions here, but I think my question is different.

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  • How to verify the Liskov substitution principle in an inheritance hierarchy?

    - by Songo
    Inspired by this answer: Liskov Substitution Principle requires that Preconditions cannot be strengthened in a subtype. Postconditions cannot be weakened in a subtype. Invariants of the supertype must be preserved in a subtype. History constraint (the "history rule"). Objects are regarded as being modifiable only through their methods (encapsulation). Since subtypes may introduce methods that are not present in the supertype, the introduction of these methods may allow state changes in the subtype that are not permissible in the supertype. The history constraint prohibits this. I was hoping if someone would post a class hierarchy that violates these 4 points and how to solve them accordingly. I'm looking for an elaborate explanation for educational purposes on how to identify each of the 4 points in the hierarchy and the best way to fix it. Note: I was hoping to post a code sample for people to work on, but the question itself is about how to identify the faulty hierarchies :)

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  • Law of Demeter confusion [duplicate]

    - by user2158382
    This question already has an answer here: Rails: Law of Demeter Confusion 4 answers I am reading a book called Rails AntiPatterns and they talk about using delegation to to avoid breaking the Law of Demeter. Here is their prime example: They believe that calling something like this in the controller is bad (and I agree) @street = @invoice.customer.address.street Their proposed solution is to do the following: class Customer has_one :address belongs_to :invoice def street address.street end end class Invoice has_one :customer def customer_street customer.street end end @street = @invoice.customer_street They are stating that since you only use one dot, you are not breaking the Law of Demeter here. I think this is incorrect, because you are still going through customer to go through address to get the invoice's street. I primarily got this idea from a blog post I read: http://www.dan-manges.com/blog/37 In the blog post the prime example is class Wallet attr_accessor :cash end class Customer has_one :wallet # attribute delegation def cash @wallet.cash end end class Paperboy def collect_money(customer, due_amount) if customer.cash < due_ammount raise InsufficientFundsError else customer.cash -= due_amount @collected_amount += due_amount end end end The blog post states that although there is only one dot customer.cash instead of customer.wallet.cash, this code still violates the Law of Demeter. Now in the Paperboy collect_money method, we don't have two dots, we just have one in "customer.cash". Has this delegation solved our problem? Not at all. If we look at the behavior, a paperboy is still reaching directly into a customer's wallet to get cash out. Can somebody help me clear the confusion. I have been searching for the past 2 days trying to let this topic sink in, but it is still confusing.

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  • How selective do we need to be for an index to be used?

    - by TiborKaraszi
    You know the answer already: It depends. But I often see some percentage value quoted and the point of this post is to show that there is no such percentage value. To get the most out of this blog post, you should understand the basic structure for an index, i.e. how the b+ tree look like. You should also understand the difference between a clustered and a non-clustered index. In essence, you should be able to visualize these structures and searches through them as you read the text. If you find...(read more)

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  • The Column Prediction_Status, MDP_Matrix and Engine. How are they Related? Understand Prediction_status Values

    - by user702295
    Do you know what these values are telling you? COUNT(*) PREDICTION_STATUS DO_FORE DO_AGGRI AGGRI_98 AGGRI_99 LEVEL_ID 19854 99 1 1 1 1 3 1077 99 0 1 1 1 0 262691 99 1 1 -1 56 99 0 1 1 1 2 1 98 1 1 1 1 1 99 0 1 1 1 748796 1 1 1 4 351633 1 1 1 1 1 2 1877829 97 1 1 4 840 99 1 1 1 1 27 99 0 1 1 1 3 1 97 1 1 -1 66712 99 1 1 1 1 2 53213 1 1 1 1 1 3 2560 98 1 1 4   Check out The Column Prediction_Status, MDP_Matrix and Engine. How are they Related? Understand Prediction_status Values (Doc ID 1509754.1) This customer is adding an additional processing burden, adding no value.  The incoming data should be scrubbed to eliminate the overhead. 

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  • What are the Crappy Code Games - Why should I attend?

    - by simonsabin
    This is part of a series on the Crappy Code Games The background Who can enter? What are the challenges? What are the prizes? Why should I attend? Tips on how to win Why should I attend? The crappy code games isn’t all about winning, its also about having a good time and learning about SQL Server. Even if you don’t want to enter the competition I think its valuable for you to come along to the heats and the final in Brighton as a chance to meat SQL Server bods and also to learn about SQL Server and...(read more)

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  • How to improve programming skills?

    - by Mike
    I'm very new to programming. I started learning PHP about half a year ago, so I do know something. I can write small functions, I can export and import information from a database and I can make a website. I don't know OOP principles and I don't know about objects and classes. Should I move to OOP principles and learn about classes, methods and objects? If not, what should I do? Continue writing simple code? How can a programmer write his/her own API? Is OOP necessary to do this? So how can i improve my skills? I love programming. I spend my 24/7 on it, so any help will be appreciated.

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  • Is having 'Util' classes a cause for concern? [closed]

    - by Matt Fenwick
    I sometimes create 'Util' classes which primarily serve to hold methods and values that don't really seem to belong elsewhere. But every time I create one of these classes, I think "uh-oh, I'm gonna regret this later ...", because I read somewhere that it's bad. But on the other hand, there seem to be two compelling (at least for me) cases for them: implementation secrets that are used in multiple classes within a package providing useful functionality to augment a class, without cluttering its interface Am I on the way to destruction? What you say !! Should I refactor?

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  • Set-based Speed Phreakery: The FIFO Stock Inventory SQL Problem

    The SQL Speed Freak Challenge is a no-holds-barred competition to find the fastest way in SQL Server to perform a real-life database task. It is the programming equivalent of drag racing, but without the commentary box. Kathi has stepped in to explain what happened with the second challenge and why some SQL ran faster than others.

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  • nagios3 Error: Could not read object configuration data!

    - by user1493730
    I have a brand new install of nagios3 on ubuntu 12.04. After I log in to the web interface and click any link I get the error: Error: Could not read object configuration data! Here are some things you should check in order to resolve this error: Verify configuration options using the -v command-line option to check for errors. Check the Nagios log file for messages relating to startup or status data errors. I ran it with the -v option and it reported no errors: Total Warnings: 0 Total Errors: 0 Things look okay - No serious problems were detected during the pre-flight check The nagios log and apache error log and debug log all have nothing regarding this. Does anyone know how to turn on logging that will give me some kind of useful error? Or if anyone knows how to fix this specific problem without additional logging, I guess that's okay too. Thanks!

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  • SEO for images: can I use a different (cookieless) domain?

    - by Oliver
    Hello, We want to increase the value of some of our important images by means of SEO, and we want to start serving them from a different, i.e. cookieless, domain. We want to go from http://www.example.com/images/1234.jpg to http://www.example.com/germany/bavaria/landscape.jpg which can easily be done via URL rewriting. Then on the other hand, we would like to serve the image from a completely different domain, let's say http://www.examplestatic.com/germany/bavaria/landscape.jpg, to save the overhead of sending the cookie from www.example.com. Somehow I feel that this is not a good idea because I move the image away from the content by putting it on a different domain. Can anyone shed some light on this problem? Naturally, I would just use a different subdomain, e.g. img.example.com, but we already use subdomains for languages and our cookies are valid for all subdomains of example.com, so this won't help. I'd really appreciate any hints. Cheers,

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  • Procedural object generation and unique identification

    - by 2080
    My question relates to procedural content generation and data management of the emerging objects in a database. I assume a networked game, with a server-client model. Unspecified objects in the game world are generated while the game is running with procedural algorithms (for example perlin noise). The players (/clients) can modify the properties of these objects, but have to notify the server of these changes. How could this communication address unique objects, so that both the server and the client know of which object they are speaking? Not only the inner properties of the objects can differ, but also visible, such as the position. When the player wants to select one of these objects the game has to find out the id - does anyone know which methods or algorithms can accomplish that?

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  • Fitting an established site into a CI framework

    - by David
    I manage a rather large, feature full nightmare of a site which has no end of feature creep settings/options/etc. Up to now its been coded in a procedural/functional way and would like to move to an OO,MVC setup. I'm quite new to it all but have done alot of research and feel that CodeIgniter is a code choice of framework to use to help quicken the transfer. Before looking at a framework, I started constructing a list of objects to create classes out of: photos users forum topics forums blogs blog posts comments The trouble I have now, is I do understand where these generic/universal objects fall into the CI MVC setup. What is the best way to organise this kind of stuff? These classes can generally be used on multiple models/views/controllers.

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  • What is the ideal laptop for creative coding applications?

    - by Jason
    Hi, I am a creative coder using C++(cinder and OpenFrameworks) I am looking to upgrade from my MacBook, which slowed down to about 3fps this morning. My project involves particles systems and fluids reacting to audio analysis data and computer vision data in real-time. SD or HD? no biggie. I have asked many people what computer I need. Ideally, I want a MacBook Pro. But is that enough power? I've been told that I need a desktop for what I am doing though I'd rather stay portable I've been told that I should go PC linux to get the most power but I'd rather stay mac I've been told that RAM is more of bottleneck than processor speed I've been told that the Graphics Card is more important than CPU and that code optimizations such as using trees over lists, proper threading, sending tasks to the GPU make a bigger difference than the hardware!!! what's true?! what do I need? Any suggestions are greatly appreciated

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  • Slow USB 3.0 speeds

    - by Cygnus X
    Long time forum forager, first time poster. I bought a Toshiba 500 GB usb 3.0 hard drive last week and instantly ran home to see how fast I could push it. On my desktop (that I built) I was able to get 200 MB/sec. On my laptop (MSI FX something or other), which I dual boot Windows 7/Ubuntu 11.10, I was able to get about 120 MB/sec on Windows, but on Ubuntu, i get about 25 MB/sec. lsusb shows: Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub Bus 001 Device 002: ID 8087:0020 Intel Corp. Integrated Rate Matching Hub Bus 002 Device 002: ID 8087:0020 Intel Corp. Integrated Rate Matching Hub Bus 001 Device 003: ID 0bda:0139 Realtek Semiconductor Corp. Bus 002 Device 003: ID 1532:0015 Razer USA, Ltd Bus 004 Device 002: ID 0480:a007 Toshiba America Info. Systems, Inc. lspci -vvv shows that the USB 3.0 host controller is using the kernel driver in use is xhci_hcd. dmesg |grep usb shows: [ 1815.455368] usb 4-1: new SuperSpeed USB device number 2 using xhci_hcd [ 1815.475459] scsi7 : usb-storage 4-1:1.0 The built in disk utility says its connected via usb at 705 MB/s, but that's not what it reports when I transfer files over to it. Not really sure what to do at this point. Any help would be very nice, thank you.

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  • How can I access bitmaps created in another activity?

    - by user22241
    I am currently loading my game bitmaps when the user presses 'start' in my animated splash screen activity (the first / launch activity) and the app progresses from my this activity to the main game activity, This is causing choppy animation in the splashscreen while it loads/creates the bitmaps for the new activity. I've been told that I should load all my bitmaps in one go at the very beginning. However, I can't work out how to do this - could anyone please point me in the right direction? I have 2 activities, a splash screen and the main game. Each consist of a class that extends activity and a class that extends SurfaceView (with an inner class for the rendering / logic updating). So, for example at the moment I am creating my bitmaps in the constructor of my SurfaceView class like so: public class OptionsScreen extends SurfaceView implements SurfaceHolder.Callback { //Create variables here public OptionsScreen(Context context) { Create bitmaps here } public void intialise(){ //This method is called from onCreate() of corresponding application context // Create scaled bitmaps here (from bitmaps previously created) }

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  • Fetching database query through function

    - by Shubham Maurya
    I am sick of connecting database in each script i need a more OOP approach to fetching database results. ex like wordpress use wpdb class to fetch results. This what wordpress does to get data <?php $posts = $wpdb->get_results("SELECT ID, post_title FROM $wpdb->posts WHERE post_status = 'publish' AND post_type='post' ORDER BY comment_count DESC LIMIT 0,4") ?> How can i create the same feature too using any class or function and use it in my script Thank you

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  • Java word scramble game [closed]

    - by Dan
    I'm working on code for a word scramble game in Java. I know the code itself is full of bugs right now, but my main focus is getting a vector of strings broken into two separate vectors containing hints and words. The text file that the strings are taken from has a colon separating them. So here is what I have so far. public WordApp() { inputRow = new TextInputBox(); inputRow.setLocation(200,100); phrases = new Vector <String>(FileUtilities.getStrings()); v_hints = new Vector<String>(); v_words = new Vector<String>(); textBox = new TextBox(200,100); textBox.setLocation(200,200); textBox.setText(scrambled + "\n\n Time Left: \t" + seconds/10 + "\n Score: \t" + score); hintBox = new TextBox(200,200); hintBox.setLocation(300,400); hintBox.hide(); Iterator <String> categorize = phrases.iterator(); while(categorize.hasNext()) { int index = phrases.indexOf(":"); String element = categorize.next(); v_words.add(element.substring(0,index)); v_hints.add(element.substring(index +1)); phrases.remove(index); System.out.print(index); } The FileUtilities file was given to us by the pofessor, here it is. import java.util.*; import java.io.*; public class FileUtilities { private static final String FILE_NAME = "javawords.txt"; //------------------ getStrings ------------------------- // // returns a Vector of Strings // Each string is of the form: word:hint // where word contains no spaces. // The words and hints are read from FILE_NAME // // public static Vector<String> getStrings ( ) { Vector<String> words = new Vector<String>(); File file = new File( FILE_NAME ); Scanner scanFile; try { scanFile = new Scanner( file); } catch ( IOException e) { System.err.println( "LineInput Error: " + e.getMessage() ); return null; } while ( scanFile.hasNextLine() ) { // read the word and follow it by a colon String s = scanFile.nextLine().trim().toUpperCase() + ":"; if( s.length()>1 && scanFile.hasNextLine() ) { // append the hint and add to collection s+= scanFile.nextLine().trim(); words.add(s); } } // shuffle Collections.shuffle(words); return words; } }

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  • Deletes that Split Pages and Forwarded Ghosts

    - by Paul White
    Can DELETE operations cause pages to split? Yes. It sounds counter-intuitive on the face of it; deleting rows frees up space on a page, and page splitting occurs when a page needs additional space. Nevertheless, there are circumstances when deleting rows causes them to expand before they can be deleted. The mechanism at work here is row versioning (extract from Books Online below): Isolation Levels The relationship between row-versioning isolation levels (the first bullet point) and page splits is...(read more)

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