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• TDD - Outside In vs Inside Out

  - by Songo

  What is the difference between building an application Outside In vs building it Inside Out using TDD? These are the books I read about TDD and unit testing: Test Driven Development: By Example Test-Driven Development: A Practical Guide: A Practical Guide Real-World Solutions for Developing High-Quality PHP Frameworks and Applications Test-Driven Development in Microsoft .NET xUnit Test Patterns: Refactoring Test Code The Art of Unit Testing: With Examples in .Net Growing Object-Oriented Software, Guided by Tests---This one was really hard to understand since JAVA isn't my primary language :) Almost all of them explained TDD basics and unit testing in general, but with little mention of the different ways the application can be constructed. Another thing I noticed is that most of these books (if not all) ignore the design phase when writing the application. They focus more on writing the test cases quickly and letting the design emerge by itself. However, I came across a paragraph in xUnit Test Patterns that discussed the ways people approach TDD. There are 2 schools out there Outside In vs Inside Out. Sadly the book doesn't elaborate more on this point. I wish to know what is the main difference between these 2 cases. When should I use each one of them? To a TDD beginner which one is easier to grasp? What is the drawbacks of each method? Is there any materials out there that discuss this topic specifically?

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• Free Team Foundation Service a Boon for Play Projects

  - by Ken Cox [MVP]

  My ‘jump in and sink or swim’ learning style leads me to create dozens of unbillable ‘play’ projects in Visual Studio 2012.  For example, I’m currently learning to customize the powerful auction/fixed price/classifieds software called AuctionWorx Enterprise.  I make stupid mistakes as I grasp a new API and configure projects. It’s frustrating to go down a rat hole and discover the VS IDE’s Undo doesn’t reach back to a working build from the previous weekend. Enter Visual Studio’s Free Team Foundation Service.  Put your play projects into the free source control and check in (or shelve) a snapshot before embarking on something risky. (I already use Discount ASP.NET’s Team Foundation Server hosting for client projects so there’s zero TFS/VS learning curve for me and first class GUI support.) TFS is free right now for teams of five or fewer. I’m not naive enough to expect ‘free’ to last forever. So, it’ll be interesting to see how much Microsoft intends to charge in 2013 for TFS. In the meantime, why not grab some free source code storage? BTW, it’s weird to realize that Microsoft is backing up my junky little playtime code on three physically-distinct servers every day - and taking incremental backups every hour.

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• Implementing game rules in a tactical battle board game

  - by Setzer22

  I'm trying to create a game similar to what one would find in a typical D&D board game combat. For mor examples you could think of games like Advance Wars, Fire Emblem or Disgaea. I should say that I'm using design by component so far, but I can't find a nice way to fit components into the part I want to ask. I'm struggling right now with the "game rules" logic. That is, the code that displays the menu, allows the player to select units, and command them, then tells the unit game objects what to do given the player input. The best way I could thing of handling this was using a big state machine, so everything that could be done in a "turn" is handled by this state machine, and the update code of this state machine does different things depending on the state. This approach, though, leads to a large amount of code (anything not model-related) to go into a big class. Of course I can subdivide this big class into more classes, but it doesn't feel modular and upgradable enough. I'd like to know of better systems to handle this in order to be able to upgrade the game with new rules without having a monstruous if/else chain (or switch / case, for that matter). So, any ideas? I'd also like to ask that if you recommend me a specific design pattern to also provide some kind of example or further explanation and not stick to "Yeah you should use MVC and it'll work".

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• How to use the unit of work and repository patterns in a service oriented enviroment

  - by A. Karimi

  I've created an application framework using the unit of work and repository patterns for it's data layer. Data consumer layers such as presentation depend on the data layer design. For example a CRUD abstract form has a dependency to a repository (IRepository). This architecture works like a charm in client/server environments (Ex. a WPF application and a SQL Server). But I'm looking for a good pattern to change or reuse this architecture for a service oriented environment. Of course I have some ideas: Idea 1: The "Adapter" design pattern Keep the current architecture and create a new unit of work and repository implementation which can work with a service instead of the ORM. Data layer consumers are loosely coupled to the data layer so it's possible but the problem is about the unit of work; I have to create a context which tracks the objects state at the client side and sends the changes to the server side on calling the "Commit" (Something that I think the RIA has done for Silverlight). Here the diagram: ----------- CLIENT----------- | ------------------ SERVER ---------------------- [ UI ] -> [ UoW/Repository ] ---> [ Web Services ] -> [ UoW/Repository ] -> [DB] Idea 2: Add another layer Add another layer (let say "local services" or "data provider"), then put it between the data layer (unit of work and repository) and the data consumer layers (like UI). Then I have to rewrite the consumer classes (CRUD and other classes which are dependent to IRepository) to depend on another interface. And the diagram: ----------------- CLIENT ------------------ | ------------------- SERVER --------------------- [ UI ] -> [ Local Services/Data Provider ] ---> [ Web Services ] -> [ UoW/Repository ] -> [DB] Please note that I have the local services layer on the current architecture but it doesn't expose the data layer functionality. In another word the UI layer can communicate with both of the data and local services layers whereas the local services layer also uses the data layer. | | | | | | | | ---> | Local Services | ---> | | | UI | | | | Data | | | | | | | ----------------------------> | |

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• How common is prototyping as the first stage of development?

  - by EpsilonVector

  I've been taking some software design courses in the past few semesters, and while I see the benefit in a lot of the formalism, I feel like it doesn't tell me anything about the program itself: You can't tell how the program is going to operate from the Use Case spec, even though it discusses what the program can do. You can't tell anything about the user experience from the requirements document, even though it can include quality requirements. Sequence diagrams are a good description of how the software works as the call stack, but are very limited, and give a highly partial view of the overall system. Class diagrams are great for describing how the system is built, but are utterly useless in helping you figure out what the software needs to be. Where in all this formalism is the bottom line: how the program looks, operates, and what experience it gives? Doesn't it make more sense to design off of that? Isn't it better to figure out how the program should work via a prototype and strive to implement it for real? I know that I'm probably suffering from being taught engineering by theoreticians, but I need to ask, do they do this in the industry? How do people figure out what the program actually is, not what it should conform to? Do people prototype a lot, or do they mostly use the formal tools like UML and I just didn't get the hang of using them yet?

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• How common is prototyping as the first stage of development?

  - by EpsilonVector

  I've been taking some software design courses in the past few semesters, and while I see the benefit in a lot of the formalism, I still feel like it doesn't tell me anything about the program itself. You can't tell how the program is going to operate from the Use Case spec, even though it discusses what the program can do, and you can't tell anything about the user experience from the requirements document, even though it can include QA requirements. ...sequence diagrams are as good a description of how the software works as the call stack, in other words- very limited, highly partial view of the overall system, and a class diagram is great for describing how the system is built, but is utterly useless in helping you figure out what the software needs to be. Where in all this formalism is the bottom line- how the program looks, operates, and what experience it gives? Doesn't it make more sense to design off of that? Isn't it better to figure out how the program should work via a prototype and strive to implement it for real? I know that I'm probably suffering from being taught engineering by theoreticians, but I got to ask, do they do this in the industry? How do people figure out what the program actually is, not what it should conform to? Do people prototype a lot? ...or do they mostly use the formal tools like UML and I just didn't get the hang of using them yet?

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• How to properly diagram lambda expressions or traversals through them in Architecture Explorer?

  - by MainMa

  I'm exploring a piece of code in Architecture Explorer in Visual Studio 2010 to study the relations between methods. I noticed a strange behavior. Take the following source code. It generates a hello message based on a template and a template engine, the template engine being a method (a sort of strategy pattern simplified at a maximum for demo purposes). public string GenerateHelloMessage(string personName) { return this.ApplyTemplate( this.DefaultTemplateEngine, this.GenerateLocalizedHelloTemplate(), personName); } private string GenerateLocalizedHelloTemplate() { return "Hello {0}!"; } public string ApplyTemplate( Func<string, string, string> templateEngine, string template, string personName) { return templateEngine(template, personName); } public string DefaultTemplateEngine(string template, string personName) { return string.Format(template, personName); } The graph generated from this code is this one: Change the first method from this: public string GenerateHelloMessage(string personName) { return this.ApplyTemplate( this.DefaultTemplateEngine, this.GenerateLocalizedHelloTemplate(), personName); } to this: public string GenerateHelloMessage(string personName) { return this.ApplyTemplate( (a, b) => this.DefaultTemplateEngine(a, b), this.GenerateLocalizedHelloTemplate(), personName); } and the graph becomes: While semantically identical, those two versions of code produce different dependency graphs, and Architecture Explorer shows no trace of the lambda expression (while Visual Studio's code coverage, for example, shows them, as well as Code analysis seems to be able to understand that the link exists). How would it be possible, without changing the source code, to: Either force Architecture Explorer to display everything, including lambda expressions, Or make it traverse lambda expressions while drawing a dependency through them (so in this case, drawing the dependency from GenerateHelloMessage to DefaultTemplateEngine in the second example)?

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• Capitalizing on JavaScript's prototypal inheritance

  - by keithjgrant

  JavaScript has a class-free object system in which objects inherit properties directly from other objects. This is really powerful, but it is unfamiliar to classically trained programmers. If you attempt to apply classical design patterns directly to JavaScript, you will be frustrated. But if you learn to work with JavaScript's prototypal nature, your efforts will be rewarded. ... It is Lisp in C's clothing. -Douglas Crockford What does this mean for a game developer working with canvas and HTML5? I've been looking over this question on useful design patterns in gaming, but prototypal inheritance is very different than classical inheritance, and there are surely differences in the best way to apply some of these common patterns. For example, classical inheritance allows us to create a moveableEntity class, and extend that with any classes that move in our game world (player, monster, bullet, etc.). Sure, you can strongarm JavaScript to work that way, but in doing so, you are kind of fighting against its nature. Is there a better approach to this sort of problem when we have prototypal inheritance at our fingertips?

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• Be liberal in what you accept... or not?

  - by Matthieu M.

  [Disclaimer: this question is subjective, but I would prefer getting answers backed by facts and/or reflexions] I think everyone knows about the Robustness Principle, usually summed up by Postel's Law: Be conservative in what you send; be liberal in what you accept. I would agree that for the design of a widespread communication protocol this may make sense (with the goal of allowing easy extension), however I have always thought that its application to HTML / CSS was a total failure, each browser implementing its own silent tweak detection / behavior, making it near impossible to obtain a consistent rendering across multiple browsers. I do notice though that there the RFC of the TCP protocol deems "Silent Failure" acceptable unless otherwise specified... which is an interesting behavior, to say the least. There are other examples of the application of this principle throughout the software trade that regularly pop up because they have bitten developpers, from the top off my head: Javascript semi-colon insertion C (silent) builtin conversions (which would not be so bad if it did not truncated...) and there are tools to help implement "smart" behavior: name matching phonetic algorithms (Double Metaphone) string distances algorithms (Levenshtein distance) However I find that this approach, while it may be helpful when dealing with non-technical users or to help users in the process of error recovery, has some drawbacks when applied to the design of library/classes interface: it is somewhat subjective whether the algorithm guesses "right", and thus it may go against the Principle of Least Astonishment it makes the implementation more difficult, thus more chances to introduce bugs (violation of YAGNI ?) it makes the behavior more susceptible to change, as any modification of the "guess" routine may break old programs, nearly excluding refactoring possibilities... from the start! And this is what led me to the following question: When designing an interface (library, class, message), do you lean toward the robustness principle or not ? I myself tend to be quite strict, using extensive input validation on my interfaces, and I was wondering if I was perhaps too strict.

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• How or why would this mechanic (not) work to bring game balance to a singleplayer RPG? [closed]

  - by 0xFFF1

  Mechanic details The player, the monsters, and the merchants act as three separate parties. The player needs to beat up monsters for exp points and resources to sell and to buy potions from merchants to continue to fight. The monsters need healing and reviving to survive (also bought from merchants) and the merchants need potion ingredients from the player and the monsters to make potions to sell. These potions are only able to be processed in such bulk by merchants thus their potions would be cheaper than making them yourself. Only the monsters can farm ingredients in bulk. Only the player is or has to be overly aggressive (in bulk). Monsters can farm and produce "Level up candies" that do the work of exp. they are eaten right away after they are made and are never stockpiled or held for fear of the player and merchants who want to sell to the player. The monsters will defend themselves. Reviving is very expensive. The merchants can be found either with a concerned expression or a grinning expression based on how much profit they are making compared to their morale standing. The economies of each monster town and merchant city are distinct but interconnected. Magic Swords are worth a lot. So what I need to know is what concerns would there be to design a game around this mechanic and/or design this mechanic around a developing game. which would fare better? Is game balance an issue here? (how strong the monsters get or how quickly they die off based on the player's input into the system), Or is game balance solely in the hands of the player? (he decides if he overkills monsters or get underleveled.) What do I need to think about to make sure it isn't too easy or too hard to swing the amount/strength of monsters compared to the player and the amount of profit the merchants get vs the player. Would indicating how out of whack things are getting in game help with this?

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• Testcase runner for parametrized testcases

  - by Razer

  Let me explain my situation. I'm planning a kind of test case runner for doing testcases on external devices, which are microcontroller based. Lets consider the devices: Device 1 Device 2 There exist a lot of test cases which can be run with one of the devices above. For example: Testcase 1 Testcase 2 The main reason that all the testcases can be run with any device is, that the testcases validates some standard and this software should be extensible for future devices. The testcases itself must be runnable with changing parameters. For example Testcase 1 does some Timing Verification the testcase needs as input parameter the datarate: 4800, 9600, 19200. Now hoping you understand the situation, let me explain my design questions. For implementing the test cases I thought about an Attribute based approach, like nunit does it. The more complicated problem is, how to define the parametrized testcases? Like this: Device 1: Testcase 1: datarate: 4800, 9600, 19200 Testcase 2: supply: 1, 2, 3 Device 2: Testcase 1: datarate: 9600, 19200, 38400 Testcase 2: supply: 3, 4, 5 How would you design such a framework? I've done a similar desin in python where I had for every device a XML containing the testcase definitions like: <Testcase="Testcase 1" datarate=4800/> <Testcase="Testcase 1" datarate=9600/> <Testcase="Testcase 1" datarate=19200/>

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• Unity throws SynchronizationLockException while debugging

  - by pjohnson

  I've found Unity to be a great resource for writing unit-testable code, and tests targeting it. Sadly, not all those unit tests work perfectly the first time (TDD notwithstanding), and sometimes it's not even immediately apparent why they're failing. So I use Visual Studio's debugger. I then see SynchronizationLockExceptions thrown by Unity calls, when I never did while running the code without debugging. I hit F5 to continue past these distractions, the line that had the exception appears to have completed normally, and I continue on to what I was trying to debug in the first place.In settings where Unity isn't used extensively, this is just one amongst a handful of annoyances in a tool (Visual Studio) that overall makes my work life much, much easier and more enjoyable. But in larger projects, it can be maddening. Finally it bugged me enough where it was worth researching it.Amongst the first and most helpful Google results was, of course, at Stack Overflow. The first couple answers were extensive but seemed a bit more involved than I could pull off at this stage in the product's lifecycle. A bit more digging showed that the Microsoft team knows about this bug but hasn't prioritized it into any released build yet. SO users jaster and alex-g proposed workarounds that relieved my pain--just go to Debug|Exceptions..., find the SynchronizationLockException, and uncheck it. As others warned, this will skip over SynchronizationLockExceptions in your code that you want to catch, but that wasn't a concern for me in this case. Thanks, guys; I've used that dialog before, but it's been so long I'd forgotten about it.Now if I could just do the same for Microsoft.CSharp.RuntimeBinder.RuntimeBinderException... Until then, F5 it is.

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• Blank screen after GRUB (64 bit) - cannot install Ubuntu

  - by peGGi

  My laptop's specs: Lenovo IdeaPad Z570 Intel Core i5-2410M @ 2.3Ghz 6 Gb RAM DDR3 640 Gb ATAPI Hard-disk Drive @ 5,200 RPM NVIDIA GeForce G520M with Optimus switching technology Broadcom 802.11n Network Adapter REALTEK soundcard Windows 7 Home Premium 64-bit I downloaded Ubuntu Studio 11.04 and burned the iso image onto two different DVDs, using two different programs (one DVD is RW, the other is just R). I verified the hash MD5sum thing. I get as far as GRUB with the 4 options (install, advanced install, disk verification, system rescue) but no matter which one I select, I get a blank screen and nothing happens. The DVD drive spins down after about 30 seconds. Also just before the GRUB screen I get a message saying Error: "Prefix" is not set. I'm not sure if that's relevant. I have tried all the options using both DVDs. Same thing happens. I have changed the graphics setting in BIOS to UMA or Optimus, but still happens either way. I've tried booting with the wireless switch turned off, same thing happens. I downloaded 'vanilla' Ubuntu 64-bit and burned onto a CD, and the same thing happens. I have downloaded Ubuntu 32-bit and I am able to boot from the live CD (interestingly the wireless card won't work, but that's maybe another issue). I have searched extensively through these forums and other sites but I can't see anything that will help me. Is there something I'm missing? I'd really appreciate help on this. The laptop is less than 2 weeks old. I was so looking forward to getting Ubuntu Studio up and running. I've gone about as far as my technical abilities will allow.

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• Designing web-based plugin systems correctly so they don't waste as many resources?

  - by Xeoncross

  Many CMS systems which rely on third parties for much of their code often build "plugin" or "hooks" systems to make it easy for developers to modify the codebase's actions without editing the core files. This usually means an Observer or Event design pattern. However, when you look at systems like wordpress you see that on every page they load some kind of bootstrap file from each of the plugin's folders to see if that plugin will need to run that request. Its this poor design that causes systems like wordpress to spend many extra MB's of memory loading and parsing unneeded items each page. Are there alternative ways to do this? I'm looking for ideas in building my own. For example, Is there a way to load all this once and then cache the results so that your system knows how to lazy-load plugins? In other words, the system loads a configuration file that specifies all the events that plugin wishes to tie into and then saves it for future requests? If that also performs poorly, then perhaps there is a special file-structure that could be used to make educated guesses about when certain plugins are unneeded to fullfil the request. Any ideas? If anyone wants an example of the "plugin" concept you can find one here.

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• Designing a plug-in system

  - by madflame991

  I'm working on a Java project and I would like to add a plug-in system. More precisely, I would like to let the user design his own module, pack it into a jar, leave it in a "plugins/" subfolder of my application and be done with it. I've managed to get a child classloader to instantiate objects of classes located in external jars, but now I'm facing a design dilemma: Say Joe makes a plug-in and he packs it in joeplugin.jar. I would really like Joe to have a class named "instantiation.Factory" and I would also like everyone to have this class with this exact location and name. (This factory class obviously implements a interface that I provide and through it I get what I want from the plug-in.) If Joe wouldn't be restricted in this way I would have to look into his entire jar for some class that implements my factory interface and I don't want to imagine how complicated things get. So my question is: should I enforce a strict naming convention for this single class? I have no idea how plug-in systems work.

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• Procedural content (settlement) generation

  - by instancedName

  I have, lets say, something like a homework or assignment to do. Roughly said I need to write an algorithm (pseudo code is not necessary, just in depth description) of procedure that would generate settlements, environment and a people to populate it with, as part of some larger world generation procedure. The genre of game is not specified, it could be any genre (rpg, strategy, colony simulation etc.) where interacting with large and extensive world is central to the game. Procedure should be called once per settlement. At the time of calling, world generation procedure makes geography, culture and history input available. Output should be map of the village and it's immediate area, and various potential additional information like myths, history, demographic facts etc. Bonus would be quest ant similar stuff, but that not really my focus at the moment. I will leave quality of the output for later when I actually dig little deeper into this topic. I am free to change parameters as long as I have strong explanation for doing so. Setting of the game is undetermined so I am free to use anything that I like the most. Ok, so my actual question is: Can anyone who has some experience in this field of game design recommend me some good literature, or point me in the direction where I should look/reed/study? I'm somewhat experienced game programmer, but I've never been into game design till now so any help will be great. I want to do this assignment as good as I can. As for deadline, it's not strictly set, but lets say I don't want it to take longer then few weeks, one month at worst case.

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• First Project a big one, How much should we charge?

  - by confuzzled

  Two of my cousins and I started a freelance computer repair/web design business just to make some money on the side during college, and received our first major web design project about three weeks ago. Now we've created websites before, but it was mostly for family businesses and have never really charged money, and most of the websites have been static, and don't really require a CMS. This project, however, was a big one (for us anyways). We created a news site that had several categories, we created the banners, we created a classifieds page (not a web app just something static that they control). Several links, a few graphical assets, CSS drop down menu, RSS feed from a different news site, weather, all the normal stuff you would find on a regular news site. On top of that we put in all the usual Joomla stuff (search, Jcomments, Jslide pictures, JCE, etc.). Then we uploaded the first 10 articles they gave us, and we are going to train them how to use Joomla. Now, at first we decided for 700 dollars. I assumed they just wanted a simple blog like website where they can upload articles. But then we had a meeting, and they asked for a lot more. Note: we did not hard code the template from scratch, but customized the gantry framework to fit their needs. We did code quite a bit however. I estimate that we put in about 50-60 hours in total. I'm wondering if 700 dollars is a bit low, this price is definitely not set in stone. Please keep in mind that this is our first project, and we are newbies, please be kind. Thank You!

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• What do you wish language designers paid attention to?

  - by Berin Loritsch

  The purpose of this question is not to assemble a laundry list of programming language features that you can't live without, or wish was in your main language of choice. The purpose of this question is to bring to light corners of languge design most language designers might not think about. So, instead of thinking about language feature X, think a little more philisophically. One of my biases, and perhaps it might be controversial, is that the softer side of engineering--the whys and what fors--are many times more important than the more concrete side. For example, Ruby was designed with a stated goal of improving developer happiness. While your opinions may be mixed on whether it delivered or not, the fact that was a goal means that some of the choices in language design were influenced by that philosophy. Please do not post: Syntax flame wars (I could care less whether you use whitespace [Python], keywords [Ruby], or curly braces [Java, C/C++, et. al.] to denote program blocks). That's just an implementation detail. "Any language that doesn't have feature X doesn't deserve to exist" type comments. There is at least one reason for all programming languages to exist--good or bad. Please do post: Philisophical ideas that language designers seem to miss. Technical concepts that seem to be poorly implemented more often than not. Please do provide an example of the pain it causes and if you have any ideas of how you would prefer it to function. Things you wish were in the platform's common library but seldom are. One the same token, things that usually are in a common library that you wish were not. Conceptual features such as built in test/assertion/contract/error handling support that you wish all programming languages would implement properly--and define properly. My hope is that this will be a fun and stimulating topic.

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• Making money from a custom built interpreter?

  - by annoying_squid

  I have been making considerable progress lately on building an interpreter. I am building it from NASM assembly code (for the core engine) and C (cl.exe the Microsoft compiler for the parser). I really don't have a lot of time but I have a lot of good ideas on how to build this so it appeals to a certain niche market. I'd love to finish this but I need to face reality here ... unless I can make some good monetary return on my investment, there is not a lot of time for me to invest. So I ask the following questions to anyone out there, especially those who have experience in monetizing their programs: 1) How easy is it for a programmer to make good money from one design? (I know this is vague but it will be interesting to hear from those who have experience or know of others' experiences). 2) What are the biggest obstacles to making money from a programming design? 3) For the parser, I am using the Microsoft compiler (no IDE) I got from visual express, so will this be an issue? Will I have to pay royalties or a license fee? 4) As far as I know NASM is a 2-clause BSD licensed application. So this should allow me to use NASM for commericial development unless I am missing something? It's good to know these things before launching into the meat and potatoes of the project.

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• Testing of visualization projects

  - by paxRoman

  We develop small to large visualization projects for different tasks and industries and sometimes while rewriting them a couple of times in the process we hit walls because we discover that we need to add a lot of code to support new requirements. Now we have established a design process that seems to work well (at least we reduced the development time for each new project quite a bit), but we're still left scratching our heads around this question: what exactly should we test when testing visualizations? If everything that we want to explore is on the screen (bounded visualizations)? If the data is ok - if data is valid (that's one of the nice things about visualizations you can spot errors in your datasets)? Usability? User interaction? Code quality? I can tell you for sure that a simple check of the code quality is certainly not enough! Is there a classic paper / book about how to test visualizations? Also do you happen to know about classic design patterns for visualizations (except the obvious ones like Pub-Sub)?

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• Is there a canonical source supporting "all-surrogates"?

  - by user61852

  Background The "all-PK-must-be-surrogates" approach is not present in Codd's Relational Model or any SQL Standard (ANSI, ISO or other). Canonical books seems to elude this restrictions too. Oracle's own data dictionary scheme uses natural keys in some tables and surrogate keys in other tables. I mention this because these people must know a thing or two about RDBMS design. PPDM (Professional Petroleum Data Management Association) recommend the same canonical books do: Use surrogate keys as primary keys when: There are no natural or business keys Natural or business keys are bad ( change often ) The value of natural or business key is not known at the time of inserting record Multicolumn natural keys ( usually several FK ) exceed three columns, which makes joins too verbose. Also I have not found canonical source that says natural keys need to be immutable. All I find is that they need to be very estable, i.e need to be changed only in very rare ocassions, if ever. I mention PPDM because these people must know a thing or two about RDBMS design too. The origins of the "all-surrogates" approach seems to come from recommendations from some ORM frameworks. It's true that the approach allows for rapid database modeling by not having to do much business analysis, but at the expense of maintainability and readability of the SQL code. Much prevision is made for something that may or may not happen in the future ( the natural PK changed so we will have to use the RDBMS cascade update funtionality ) at the expense of day-to-day task like having to join more tables in every query and having to write code for importing data between databases, an otherwise very strightfoward procedure (due to the need to avoid PK colisions and having to create stage/equivalence tables beforehand ). Other argument is that indexes based on integers are faster, but that has to be supported with benchmarks. Obviously, long, varying varchars are not good for PK. But indexes based on short, fix-length varchar are almost as fast as integers. The questions - Is there any canonical source that supports the "all-PK-must-be-surrogates" approach ? - Has Codd's relational model been superceded by a newer relational model ?

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• Web Services and code lists

  - by 0x0me

  Our team heavily discuss the issues how to handle code list in a web service definition. The design goal is to describe a provider API to query a system using various values. Some of them are catalogs resp. code lists. A catalog or code list is a set of key value pairs. There are different systems (at least 3) maintaining possibly different code lists. Each system should implement the provider API, whereas each system might have different code list for the same business entity eg. think of colors. One system know [(1,'red'),(2,'green')] and another one knows [(1,'lightgreen'),(2,'darkgreen'),(3,'red')] etc. The access to the different provider API implementations will be encapsulated by a query service, but there is already one candidate which might use at least one provider API directly. The current options to design the API discussed are: use an abstract code list in the interface definition: the web service interface defines a well known set of code list which are expected to be used for querying and returning data. Each API provider implementation has to mapped the request and response values from those abstract codelist to the system specific one. let the query component handle the code list: the encapsulating query service knows the code list set of each provider API implementation and takes care of mapping the input and output to the system specific code lists of the queried system. do not use code lists in the query definition at all: Just query code lists by a plain string and let the provider API implementation figure out the right value. This might lead to a loose of information and possibly many false positives, due to the fact that the input string could not be canonical mapped to a code list value (eg. green - lightgreen or green - darkgreen or both) What are your experiences resp. solutions to such a problem? Could you give any recommendation?

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• Looking for a better Factory pattern (Java)

  - by Sam Goldberg

  After doing a rough sketch of a high level object model, I am doing iterative TDD, and letting the other objects emerge as a refactoring of the code (as it increases in complexity). (That whole approach may be a discussion/argument for another day.) In any case, I am at the point where I am looking to refactor code blocks currently in an if-else blocks into separate objects. This is because there is another another value combination which creates new set of logical sub-branches. To be more specific, this is a trading system feature, where buy orders have different behavior than sell orders. Responses to the orders have a numeric indicator field which describes some event that occurred (e.g. fill, cancel). The combination of this numeric indicator field plus whether it is a buy or sell, require different processing buy the code. Creating a family of objects to separate the code for the unique handling each of the combinations of the 2 fields seems like a good choice at this point. The way I would normally do this, is to create some Factory object which when called with the 2 relevant parameters (indicator, buysell), would return the correct subclass of the object. Some times I do this pattern with a map, which allows to look up a live instance (or constructor to use via reflection), and sometimes I just hard code the cases in the Factory class. So - for some reason this feels like not good design (e.g. one object which knows all the subclasses of an interface or parent object), and a bit clumsy. Is there a better pattern for solving this kind of problem? And if this factory method approach makes sense, can anyone suggest a nicer design?

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• Using visitor pattern with large object hierarchy

  - by T. Fabre

  Context I've been using with a hierarchy of objects (an expression tree) a "pseudo" visitor pattern (pseudo, as in it does not use double dispatch) : public interface MyInterface { void Accept(SomeClass operationClass); } public class MyImpl : MyInterface { public void Accept(SomeClass operationClass) { operationClass.DoSomething(); operationClass.DoSomethingElse(); // ... and so on ... } } This design was, however questionnable, pretty comfortable since the number of implementations of MyInterface is significant (~50 or more) and I didn't need to add extra operations. Each implementation is unique (it's a different expression or operator), and some are composites (ie, operator nodes that will contain other operator/leaf nodes). Traversal is currently performed by calling the Accept operation on the root node of the tree, which in turns calls Accept on each of its child nodes, which in turn... and so on... But the time has come where I need to add a new operation, such as pretty printing : public class MyImpl : MyInterface { // Property does not come from MyInterface public string SomeProperty { get; set; } public void Accept(SomeClass operationClass) { operationClass.DoSomething(); operationClass.DoSomethingElse(); // ... and so on ... } public void Accept(SomePrettyPrinter printer) { printer.PrettyPrint(this.SomeProperty); } } I basically see two options : Keep the same design, adding a new method for my operation to each derived class, at the expense of maintainibility (not an option, IMHO) Use the "true" Visitor pattern, at the expense of extensibility (not an option, as I expect to have more implementations coming along the way...), with about 50+ overloads of the Visit method, each one matching a specific implementation ? Question Would you recommand using the Visitor pattern ? Is there any other pattern that could help solve this issue ?

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• ASP.NET Webforms developers and web designers: how to interact?

  - by just_name

  I'm an ASP.NET Webforms developer, and I face some problems when I deal with designers. Designers always complain about the asp.net server controls. They'd rather just have an html file and create css files along with the required images to go with those. Sometimes, if the design phase is done in advance, I get html files with related css files, but then we face many problems integrating the design with the aspx files (sever controls an telerik controls ... etc). What I want to ask about is: How do I overcome these problems? The designers prefer php- and mvc developers because of the problems with .net server controls. I need to know how to interact with the designers in the correct way. Are there any tools or applications to provide the designers with the rendered (html page) of the .aspx pages? By that I mean the page in runtime rather than the aspx in Visual Studio. They do use Web Expression but they want the rendered page in html as well.

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