Top-down or bottom-up design?
- by Gabriel Šcerbák
There are basically those two approaches to designing a system. What are the advantages and disadvantages? When should I use which? Should I combine those approaches? How?
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Java Program Design Layout Recommendations?
- by Leebuntu
I've learned enough to begin writing programs from scratch, but I'm running into the problem of not knowing how to design the layout and implementation of a program. To be more precise, I'm having difficulty finding a good way to come up with an action plan before I dive in to the programming part. I really want to know what classes, methods, and objects I would need beforehand instead of just adding them along the way. My intuition is leading me to using some kind of charting software that gives a hierarchal view of all the classes and methods. I've been using OmniGraffle Pro and while it does seem to work somewhat, I'm still having trouble planning out the program in its entirety. How should I approach this problem? What softwares out there are available to help with this problem? Any good reads out there on this issue? Thanks so much! Edit: Oh yeah, I'm using Eclipse and I code mainly in Java right now.Read the article
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Windows Services -- High availability scenarios and design approach
- by Vadi
Let's say I have a standalone windows service running in a windows server machine. How to make sure it is highly available? 1). What are all the design level guidelines that you can propose? 2). How to make it highly available like primary/secondary, eg., the clustering solutions currently available in the market 3). How to deal with cross-cutting concerns in case any fail-over scenarios If any other you can think of please add it here .. Note: The question is only related to windows and windows services, please try to obey this rule :)Read the article
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'is instanceof' Interface bad design
- by peterRit
Say I have a class A class A { Z source; } Now, the context tells me that 'Z' can be an instance of different classes (say, B and C) which doesn't share any common class in their inheritance tree. I guess the naive approach is to make 'Z' an Interface class, and make classes B and C implement it. But something still doesn't convince me because every time an instance of class A is used, I need to know the type of 'source'. So all finishes in multiple 'ifs' making 'is instanceof' which doesn't sound quite nice. Maybe in the future some other class implements Z, and having hardcoded 'ifs' of this type definitely could break something. The escence of the problem is that I cannot resolve the issue by adding functions to Z, because the work done in each instance type of Z is different. I hope someone can give me and advice, maybe about some useful design pattern. ThanksRead the article
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design patterns for hierarchical structures
- by JLBarros
Anyone knows some design patterns for hierarchical structures? For example, to manage inventory categories, accounting chart of accounts, divisions of human resources, etc.. Thank you very much in advance EDIT: Thanks for your interest. I am looking for a better way of dealing with hierarchical items to which they should apply operations depending on the level of hierarchy. I have been studying the patterns by Martin Fowler, for example Accounting, but I wonder if there are other more generic. The problem is that operations apply to the items must be possible to change even at run time and may depend on other external variables. I thought of a kind of strategy pattern but would like to combine it with the fact that it is a hierarchical scheme. I would appreciate any reference to hierarchical patterns and you'll take care of them in depth.Read the article
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Needs opinions based on design guidelines .
- by Abu Hamzah
i am in the process of desigining my domain model and i know its very hard to suggest without knowledge of domain but what i am asking is how to implement or the best way of implementing the baseclass in my domain model. here are few classes: PartialPerson.cs Facilities.cs Visit.cs EntryPoint.cs etc.... my baseclass looks like this: public abstract class BaseClass { public int InfoId { get; } public int PersonId { get; } } here is what i am confused and need help. how do i implement the above baseclass? in the PartialPerson,Facilities,Visit...Read the article
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How should I handle expected errors? eg. "username already exists"
- by Pheter
I am struggling to understand how I should design the error handling parts of my code. I recently asked a similar question about how I should go about returning server error codes to the user, eg. 404 errors. I learnt that I should handle the error from within the current part of the application; seem's simple enough. However, what should I do when I can't handle the error from the current link in the chain? For example, I may have a class that is used to manage authentication. One of it's methods could be createUser($username, $password). Within that function, I need to determine if the username already exists. If this is true, how should I alert the calling code about this? Returning null instead of a user object is one way. But how do I then know what caused the error? How should I handle errors in such a way that calling code can easily find out what caused the error? Is there a design pattern commonly used for this kind of situation?Read the article
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SQL In The City Charlotte - Fundamentals of Database Design
- by drsql
Next Monday, October 14, at Red-Gate's SQL In The City conference in Charlotte, NC (one day before PASS), I will be presenting my Fundamentals of Database Design session. It is my big-time chestnut session, the one that I do the most and have the most fun with. This will be the "single" version of the session, weighing in at just under an hour, and it is a lot of material to go over (even with no code samples to go awry to take up time.) In this hour long session (presented in widescreen...(read more)Read the article
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C# Domain-Driven Design Sample Released
- by Artur Trosin
In the post I want to declare that NDDD Sample application(s) is released and share the work with you. You can access it here: http://code.google.com/p/ndddsample. NDDDSample from functionality perspective matches DDDSample 1.1.0 which is based Java and on joint effort by Eric Evans' company Domain Language and the Swedish software consulting company Citerus. But because NDDDSample is based on .NET technologies those two implementations could not be matched directly. However concepts, practices, values, patterns, especially DDD, are cross-language and cross-platform :). Implementation of .NET version of the application was an interesting journey because now as .NET developer I better understand the differences positive and negative between these two platforms. Even there are those differences they can be overtaken, in many cases it was not so hard to match a java libs\framework with .NET during the implementation. Here is a list of technology stack: 1. .net 3.5 - framework 2. VS.NET 2008 - IDE 3. ASP.NET MVC2.0 - for administration and tracking UI 4. WCF - communication mechanism 5. NHibernate - ORM 6. Rhino Commons - Nhibernate session management, base classes for in memory unit tests 7. SqlLite - database 8. Windsor - inversion of control container 9. Windsor WCF facility - for better integration with NHibernate 10. MvcContrib - and in particular its Castle WindsorControllerFactory in order to enable IoC for controllers 11. WPF - for incident logging application 12. Moq - mocking lib used for unit tests 13. NUnit - unit testing framework 14. Log4net - logging framework 15. Cloud based on Azure SDK These are not the latest technologies, tools and libs for the moment but if there are someone thinks that it would be useful to migrate the sample to latest current technologies and versions please comment. Cloud version of the application is based on Azure emulated environment provided by the SDK, so it hasn't been tested on ‘real' Azure scenario (we just do not have access to it). Thanks to participants, Eugen Gorgan who was involved directly in development, Ruslan Rusu and Victor Lungu spend their free time to discuss .NET specific decisions, Eugen Navitaniuc helped with Java related questions. Also, big thank to Cornel Cretu, he designed a nice logo and helped with some browser incompatibility issues. Any review and feedback are welcome! Thank you, Artur TrosinRead the article
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Book recommend: Start learning web design with css with basic HTML knowledge
- by Minh Hieu
I've already known some HTML, tables, link, image,...etc but just at a basic level. Now I want to learn how to build a layout for a website and design also. I want to start building a layout right a way and just learning from it, not really like reading so much theories, explanations. Many books are so verbose, they teach from the beginning of HTML or explain things too much. I don't want to waste my time. So are there any good books for me?Read the article
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Need advice on design in Ruby On Rails
- by Elad
For personal educational purposes I am making a site for a conference. One of the object that exist in a conference is a session, which has different states and in each state it has slightly different attributes: When submitted it has a speaker (User in the system), Title and abstract. When under review it has reviews and comments (in addition to the basic data) When accepted it has a defined time-slot but no reviewers anymore. I feel that it is not the best thing to add a "status" attributes and start adding many if statements... So I thought it would be better to have different classes for each state each with it's own validations and behaviors. What do you think about this design? Do you have a better idea? *I must add this out of frustration: I had several edits of the question, including one major change but no one actually gave any hint or clue on which direction should i take or where is a better place to ask this... Hardly helpful.Read the article
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Book recommend: Start learning web design with css with basic HTML knowledge
- by Hieusun2011
I've already known some HTML, tables, link, image,...etc but just at a basic level. Now I want to learn how to build a layout for a website and design also. I want to start building a layout right a way and just learning from it, not really like reading so much theories, explanations. Many books are so verbose, they teach from the beginning of HTML or explain things too much. I don't want to waste my time. So are there any good books for me?Read the article
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Design Patterns: Should I learn them?
- by prelic
So it's kinda weird asking two questions back-to-back, but they aren't very related and I didn't want to combine them, but I'm not spamming questions, I promise! Anyway, I'm a recent college grad, and my education only touched on design patterns...we implemented a few simple ones, touched on the fact that there were more complicated ones, and were instructed to turn to the GoF book if we wanted to learn more. My question is, is it worth learning the patterns in the GoF book? To me, it's always seemed counter-intuitive to try and make a problem fit a classic pattern, but obviously the book, and the patterns, are famous for a reason. Do they show up enough that I should be learning them? Thanks again!Read the article
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cocos2d-x - object creation and management in game design
- by Jason
How do others keep track of everything going on in their games? I am working on a new game and I am quickly realizing everything that I need to keep track of. Example: Maybe a layerManager that keeps track of all the layers and what is happening for a particular scene. Maybe a sceneManager for sharing objects among scenes But then getting to game play itself, what if you have 100 objects on the screen each with its own state and happenings, there needs tobe a way to keep track of all of that. Drawing everything out is really helping me. Can anyone share with me how they go about object tracking/management? I am seeing a few different managers and then maybe even a parent object that manages the managers..is my thinking way off? Any design patterns that may be useful for me to read about? Update: doing some reading and maybe a Factory pattern might apply.Read the article
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Board Game Design in Cocos2d
- by object2.0
Hi folks i am going to start a chess like board game. and for that i have reviewed a number to things available. one is http://www.mapeditor.org/ , using which you can create a grid base games. another option is geekgameboard for iphone available at http://mooseyard.lighthouseapp.com/projects/23201-geekgameboard now i want your expert opinion that would it be better to make a game in cocos2d using the first option or the second option? both looks promising to me and give good control over board design. ps: sorry for duplicates, i found about the http://gamedev.stackexchange.com/ lately after posting it on stackexchange. so i am just posting it here again as i feel its more relevant board.Read the article
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design pattern for unit testing? [duplicate]
- by Maddy.Shik
This question already has an answer here: Unit testing best practices for a unit testing newbie 4 answers I am beginner in developing test cases, and want to follow good patterns for developing test cases rather than following some person or company's specific ideas. Some people don't make test cases and just develop the way their senior have done in their projects. I am facing lot problems like object dependencies (when want to test method which persist A object i have to first persist B object since A is child of B). Please suggest some good books or sites preferably for learning design pattern for unit test cases. Or reference to some good source code or some discussion for Dos and Donts will do wonder. So that i can avoid doing mistakes be learning from experience of others.Read the article
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design pattern for unit testing?
- by Maddy.Shik
I am beginner in developing test cases, and want to follow good patterns for developing test cases rather than following some person or company's specific ideas. Some people don't make test cases and just develop the way their senior have done in their projects. I am facing lot problems like object dependencies (when want to test method which persist A object i have to first persist B object since A is child of B). Please suggest some good books or sites preferably for learning design pattern for unit test cases. Or reference to some good source code or some discussion for Dos and Donts will do wonder. So that i can avoid doing mistakes be learning from experience of others.Read the article
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Java applet game design no keyboard focus
- by Sri Harsha Chilakapati
THIS IS PROBABLY THE WRONG PLACE. POSTED ITHERE (STACKOVERFLOW) I'm making an applet game and it is rendering, the game loop is running, the animations are updating, but the keyboard input is not working. Here's an SSCCE. public class Game extends JApplet implements Runnable { public void init(){ // Initialize the game when called by browser setFocusable(true); requestFocus(); requestFocusInWindow(); // Always returning false GInput.install(this); // Install the input manager for this class new Thread(this).start(); } public void run(){ startGameLoop(); } } And Here's the GInput class. public class GInput implements KeyListener { public static void install(Component c){ new GInput(c); } public GInput(Component c){ c.addKeyListener(this); } public void keyPressed(KeyEvent e){ System.out.println("A key has been pressed"); } ...... } This is my GInput class. When run as an applet, it doesn't work and when I add the Game class to a frame, it works properly. ThanksRead the article
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Why many designs ignore normalization in RDBMS?
- by Yosi
I got to see many designs that normalization wasn't the first consideration in decision making phase. In many cases those designs included more than 30 columns, and the main approach was "to put everything in the same place" According to what I remember normalization is one of the first, most important things, so why is it dropped so easily sometimes? Edit: Is it true that good architects and experts choose a denormalized design while non-experienced developers choose the opposite? What are the arguments against starting your design with normalization in mind?Read the article
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Cheaper alternatives to 99Designs.com (outsource CSS design)
- by Chris Smith
I'm designing my own website as a side project and I want the site to look professional. (Read, not designed by a programmer.) I don't mind spending a little money to have a professional do it, but design sites like 99designs.com cost way to much. (~$500+) Is there a cheaper (~$100 - $200) alternative for getting a designer to improve an existing site? (Things like updating the CCS or suggesting better ways for laying out the navigation.) Or is my best bet trying to pick up a freelancer on Craigslist?Read the article
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Cheaper alternatives to 99Designs.com (outsource CSS design)
- by Chris Smith
I'm designing my own website as a side project and I want the site to look professional. (Read, not designed by a programmer.) I don't mind spending a little money to have a professional do it, but design sites like 99designs.com cost way to much. (~$500+) Is there a cheaper (~$100 - $200) alternative for getting a designer to improve an existing site? (Things like updating the CCS or suggesting better ways for laying out the navigation.) Or is my best bet trying to pick up a freelancer on Craigslist?Read the article
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Low-level game engine renderer design
- by Mark Ingram
I'm piecing together the beginnings of an extremely basic engine which will let me draw arbitrary objects (SceneObject). I've got to the point where I'm creating a few sensible sounding classes, but as this is my first outing into game engines, I've got the feeling I'm overlooking things. I'm familiar with compartmentalising larger portions of the code so that individual sub-systems don't overly interact with each other, but I'm thinking more of the low-level stuff, starting from vertices working up. So if I have a Vertex class, I can combine that with a list of indices to make a Mesh class. How does the engine determine identical meshes for objects? Or is that left to the level designer? Once we have a Mesh, that can be contained in the SceneObject class. And a list of SceneObject can be placed into the Scene to be drawn. Right now I'm only using OpenGL, but I'm aware that I don't want to be tying OpenGL calls right in to base classes (such as updating the vertices in the Mesh, I don't want to be calling glBufferData etc). Are there any good resources that discuss these issues? Are there any "common" heirachies which should be used?Read the article
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Serious Forum Design Issue
- by John
I want to launch a school forum for a country. I'm in dilemma as to how to design this forum. Country will have many states, each state will have cities, each city will have many schools. Each school will have many classes( 1st - 12th). It looks like this: States - Cities - Schools - Classes I want to make each class as forum. Now the biggest problems are two fold: If I were to list even 1000 schools it will create huge number of forums and I don't think forum softwares(PHPBB, MyBB) are designed to support these many Secondly creating and maintaining huge forums is also very difficult. Ideally I'd like to duplicate existing forum hierarchy to new one. I've done lot of search and I've found that such type of forums are infeasible and such designs don't work. Leave alone the fact the nobody uses such a forum. Keeping in mind this, how should I go about designing this forum?Read the article
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How granular should a command be in a CQ[R]S model?
- by Aaronaught
I'm considering a project to migrate part of our WCF-based SOA over to a service bus model (probably nServiceBus) and using some basic pub-sub to achieve Command-Query Separation. I'm not new to SOA, or even to service bus models, but I confess that until recently my concept of "separation" was limited to run-of-the-mill database mirroring and replication. Still, I'm attracted to the idea because it seems to provide all the benefits of an eventually-consistent system while sidestepping many of the obvious drawbacks (most notably the lack of proper transactional support). I've read a lot on the subject from Udi Dahan who is basically the guru on ESB architectures (at least in the Microsoft world), but one thing he says really puzzles me: As we get larger entities with more fields on them, we also get more actors working with those same entities, and the higher the likelihood that something will touch some attribute of them at any given time, increasing the number of concurrency conflicts. [...] A core element of CQRS is rethinking the design of the user interface to enable us to capture our users’ intent such that making a customer preferred is a different unit of work for the user than indicating that the customer has moved or that they’ve gotten married. Using an Excel-like UI for data changes doesn’t capture intent, as we saw above. -- Udi Dahan, Clarified CQRS From the perspective described in the quotation, it's hard to argue with that logic. But it seems to go against the grain with respect to SOAs. An SOA (and really services in general) are supposed to deal with coarse-grained messages so as to minimize network chatter - among many other benefits. I realize that network chatter is less of an issue when you've got highly-distributed systems with good message queuing and none of the baggage of RPC, but it doesn't seem wise to dismiss the issue entirely. Udi almost seems to be saying that every attribute change (i.e. field update) ought to be its own command, which is hard to imagine in the context of one user potentially updating hundreds or thousands of combined entities and attributes as it often is with a traditional web service. One batch update in SQL Server may take a fraction of a second given a good highly-parameterized query, table-valued parameter or bulk insert to a staging table; processing all of these updates one at a time is slow, slow, slow, and OLTP database hardware is the most expensive of all to scale up/out. Is there some way to reconcile these competing concerns? Am I thinking about it the wrong way? Does this problem have a well-known solution in the CQS/ESB world? If not, then how does one decide what the "right level" of granularity in a Command should be? Is there some "standard" one can use as a starting point - sort of like 3NF in databases - and only deviate when careful profiling suggests a potentially significant performance benefit? Or is this possibly one of those things that, despite several strong opinions being expressed by various experts, is really just a matter of opinion?Read the article
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Software development, basics of design, conventions and scalability
- by goce ribeski
I need to improve my programming skills in order to achieve better scalability for the software I'm working on. Purpose is to learn the rules of adding new modules and features, so when it comes to maintaining existing ones there is some concept. So, I'm looking for a good book, tutorial or websites where I can continue to read about this. Currently, what I know and what I do is: to design relational database(3NF), make separate class for each table put that in MVC implement modular programming ...write code and hope for the best... I presume that next things I need to learn more deeply are: programming codex(naming, commenting, conventions...), organize functions building interfaces organizing custom made libraries, organizing API that I'm using, documenting, team work... ... At last what my job is, it does't need to affect your answer, PHP CodeIgniter developer.Read the article
