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• Android Design - Service vs Thread for Networking

  - by Nevyn

  I am writing an Android app, finally (yay me) and for this app I need persistant, but user closeable, network sockets (yes, more than one). I decided to try my hand at writing my own version of an IRC Client. My design issue however, is I'm not sure how to run the Socket connectivity itself. If I put the sockets at the Activity level, they keeps getting closed shortly after the Activity becomes non-visible (also a problem that needs solving...but I think i figured that one out)...but if I run a "connectivity service", I need to find out if I can have multiple instances of it running (the service, that is...one per server/socket). Either that or a I need a way to Thread the sockets themselves and have multiple threads running that I can still communicate with directly (ID system of some sort). Thus the question: Is it a 'better', or at least more "proper" design pattern, to put the Socket and networking in a service, and have the Activities consume said service...or should I tie the sockets directly to some Threaded Process owned by the UI Activity and not bother with the service implementation at all? I do know better than to put the networking directly on the UI thread, but that's as far as I've managed to get.

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• Design pattern for animation sequence in LibGDX

  - by kevinyu

  What design pattern to use for sequence of animation that involve different actor in libGDX. For example I am making a game to choose a wolf from a group of sheeps. The first animation played when the game begin is the wolf enter the field that is filled with two sheeps.Then the wolf disguise as a sheep and goes to the center of the screen. Then the game will shuffle the sheeps. After it finished it will ask the player where is the wolf. The game wait for player input. After that the game will show animation to show the player whether their answer is right or wrong. I am currently using State design pattern. There are four states wolfEnterState,DisguiseState,ShuffleState,UserInputState, and answerAnimationState. I feel that my code is messy. I use addAction with action sequence and action completion(new Runnable()) a lot. I feel that the action sequence is getting long. Is there a better solution for this kind of problem

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• OO Design, how to model Tonal Harmony?

  - by David

  I have started to write a program in C++ 11 that would analyse chords, scales, and harmony. The biggest problem I am having in my design phase, is that the note 'C' is a note, a type of chord (Cmaj, Cmin, C7, etc), and a type of key (the key of Cmajor, Cminor). The same issue arises with intervals (minor 3rd, major 3rd). I am using a base class, Token, that is the base class for all 'symbols' in the program. so for example: class Token { public: typedef shared_ptr<Token> pointer_type; Token() {} virtual ~Token() {} }; class Command : public Token { public: Command() {} pointer_type execute(); } class Note : public Token; class Triad : public Token; class MajorTriad : public Triad; // CMajorTriad, etc class Key : public Token; class MinorKey : public Key; // Natural Minor, Harmonic minor,etc class Scale : public Token; As you can see, to create all the derived classes (CMajorTriad, C, CMajorScale, CMajorKey, etc) would quickly become ridiculously complex including all the other notes, as well as enharmonics. multiple inheritance would not work, ie: class C : public Note, Triad, Key, Scale class C, cannot be all of these things at the same time. It is contextual, also polymorphing with this will not work (how to determine which super methods to perform? calling every super class constructors should not happen here) Are there any design ideas or suggestions that people have to offer? I have not been able to find anything on google in regards to modelling tonal harmony from an OO perspective. There are just far too many relationships between all the concepts here.

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• Architectural and Design Challenges with SOA

  With all of the hype about service oriented architecture (SOA) primarily through the use of web services, not much has been said about potential issues of using SOA in the design of an application. I am personally a fan of SOA, but it is not the solution for every application. Proper evaluation should be done on all requirements and use cases prior to deciding to go down the SOA road. It is important to consider how your application/service will handle the following perils as it executes. Example Challenges of SOA Network Connectivity Issues Handling Connectivity Issues Longer Processing/Transaction Times How many of us have had issues visiting our favorite web sites from time to time? The same issue will occur when using service based architecture especially if it is implemented using web services. Forcing applications to access services via a network connection introduces a lot of new failure points to the application. Potential failure points include: DNS issues, network hardware issues, remote server issues, and the lack of physical network connections. When network connectivity issues do occur, how are the service clients are implemented is very important. Should the client wait and poll the service until it is accessible again? If so what is the maximum wait time or number of attempts it should retry. Due to the fact of services being distributed across a network automatically increase the responsiveness of client applications due to the fact that processing time must now also include time to send and receive messages from called services. This could add nanoseconds to minutes per each request based on network load and server usage of the service provider. If speed highly desirable quality attribute then I would consider creating components that are hosted where the client application is located. References: Rader, Dave. (2002). Overcoming Web Services Challenges with Smart Design: http://soa.sys-con.com/node/39458

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• Software Design Idea for multi tier architecture

  - by Preyash

  I am currently investigating multi tier architecture design for a web based application in MVC3. I already have an architecture but not sure if its the best I can do in terms of extendability and performance. The current architecure has following components DataTier (Contains EF POCO objects) DomainModel (Contains Domain related objects) Global (Among other common things it contains Repository objects for CRUD to DB) Business Layer (Business Logic and Interaction between Data and Client and CRUD using repository) Web(Client) (which talks to DomainModel and Business but also have its own ViewModels for Create and Edit Views for e.g.) Note: I am using ValueInjector for convering one type of entity to another. (which is proving an overhead in this desing. I really dont like over doing this.) My question is am I having too many tiers in the above architecure? Do I really need domain model? (I think I do when I exposes my Business Logic via WCF to external clients). What is happening is that for a simple database insert it (1) create ViewModel (2) Convert ViewModel to DomainModel for Business to understand (3) Business Convert it to DataModel for Repository and then data comes back in the same order. Few things to consider, I am not looking for a perfect architecure solution as it does not exits. I am looking for something that is scalable. It should resuable (for e.g. using design patterns ,interfaces, inheritance etc.) Each Layers should be easily testable. Any suggestions or comments is much appriciated. Thanks,

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• Which book should I pick to improve my program designs/design patterns?

  - by zxcvbnm

  I want to learn about design patterns and from what I've seen the most recommended ones are the Gang of Four's Design Patterns and Head First Design Patterns. There are also language specific books, but I never see them recommended. I suppose it ties you to whatever strengths/weaknesses are inherent to each language, so not a good idea to learn design patterns in general. The Gang of Four's book is kinda old, so I'm wondering if there isn't a better alternative out today? I've heard the Heard First one isn't quite as good. But I'm not sure why, so it's really hard to pick either one. I've see some answers on this very site recommending both, but if I can only read one, which should I pick? I've been coding for 3+ years, though I've never had a good class on this subject. Also, would a book like Code Complete help me with this? One more thing: how often are these techniques supposed to be useful? For example, this question has me wondering if this stuff is worth the trouble. And please, tell me more than just "read x". I'd like to know why you're suggesting x.

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• Experienced programmer, beginner at web design, tools for effective maintainable web design? [closed]

  - by Clinton

  I do quite a bit of programming in my work, which I'm comfortable with, but recently I've being trying to do some web-design for non-work related reasons. I've got a Drupal site up and running, and added some content. But they all look fairly basic. Header with some content. It doesn't look particularly polished. Anyway, as an example, what I wanted to do was make some "bubbles", each with some text in them. From a programmers point of view, say: bubble(question_text, answer_text) might expand to a box with some border, with "Question: " + question_text then "Answer: " + answer_text. Of course I'd have lots of these bubbles, but I'd like to change their look and feel in one place, so simple HTML would be a maintainable nightmare. I also want to lay them out on the screen in some fashion. I was thinking a mixture of javascript and CSS, or possibly use PHP which Drupal uses. On the other hand, I fear I might be taking a 1990s approach to this, and that there's actually tools available now that make this process a lot easier. I'm just wondering what the best approach to this sort of task is? Should I be using offline web design software and copying the code to Drupal, and if so, any recommendations? I'm sorry if my question is a bit vague, because I'm not really sure what question I should be asking. I'd appreciate if you answer and comment, and I'll try my best to be more specific as I understand more.

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• Design practice for securing data inside Azure SQL

  - by Sid

  Update: I'm looking for a specific design practice as we try to build-our-own database encryption. Azure SQL doesn't support many of the encryption features found in SQL Server (Table and Column encryption). We need to store some sensitive information that needs to be encrypted and we've rolled our own using AesCryptoServiceProvider to encrypt/decrypt data to/from the database. This solves the immediate issue (no cleartext in db) but poses other problems like Key rotation (we have to roll our own code for this, walking through the db converting old cipher text into new cipher text) metadata mapping of which tables and which columns are encrypted. This is simple when it's just couple of columns (send an email to all devs/document) but that quickly gets out of hand ... So, what is the best practice for doing application level encryption into a database that doesn't support encryption? In particular, what is a good design to solve the above two bullet points? If you had specific schema additions would love it if you could give details ("Have a NVARCHAR(max) column to store the cipher metadata as JSON" or a SQL script/commands). If someone would like to recommend a library, I'd be happy to stay away from "DIY" too. Before going too deep - I assume there isn't any way I can add encryption support to Azure by creating a stored procedure, right?

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• MVC design patterns

  - by insane-36

  I have an application and it does not use a very good structure. However it seems to me that I have tried to stick to mvc design pattern but a senior engineer claims that I have no design patterns and code are mesh. How I have structured the code : I have couple of nsmanagedobject model classes which represents model in my case and a reskit library which encapsulates the nsurlconnection and url request. I fetch the request from the view controller itself and then when the request get completed I create predicate and then populate it in tableview. Wherever I need custom view either I create it in nib or create in a custom subclass of UIView. I have use delegation pattern and notification to communication to view controller, views and block callback with restkit. But, the senior engineer is very new to ios. He has been doing it for 2 months now but he is a good java programmer. So, what is mvc pattern ? Is core data model not working as a model objects, view controller as controller and views. I dont seem to find any other places or any other cases to create my own model object since the most of the models are used as NSManagedObject subclass.

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• Examples of temporal database designs? [closed]

  - by miku

  I'm researching various database design for historical record keeping - because I would like to implement a prototypical web application that (excessively) tracks changes made by users and let them undo things, see revisions, etc. I'd love use mercurial or git as backend (with files as records) - since they already implement the kind of append-only changes I imagine. I tried git and dulwich (python git API) - and it went ok - but I was concerned about performance; Bi-temporal database design lets you store a row along with time periods, when this record was valid. This sure sound more performant than to operate on files on disk (as in 1.) - but I had little luck finding real-world examples (e.g. from open source projects), that use this kind of design and are approachable enough to learn from them. Revisions à la MediaWiki revisions or an extra table for versions, as in Redmine. The problem here is, that DELETE would take the whole history with it. I looked at NoSQL solutions, too. With a document oriented approach, it would be simple to just store the whole history of an entity within the document itself - which would reduce design plus implementation time in contrast to a RDBMS approach. However, in this case I'm a bit concerned about ACID-properties, which would be important in the application. I'd like ask about experiences about real-world and pragmatic designs for temporal data.

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• How to improve designer and developer work flow?

  - by mbdev

  I work in a small startup with two front end developers and one designer. Currently the process starts with the designer sending a png file with the whole page design and assets if needed. My task as front end developer is to convert it to a HTML/CSS page. My work flow currently looks like this: Lay out the distinct parts using html elements. Style each element very roughly (floats, minimal fonts and padding) so I can modify it using inspection. Using Chrome Developer Tools (inspect) add/change css attributes while updating the css file. Refresh the page after X amount of changes Use Pixel Perfect to refine the design more. Sit with the designer to make last adjustments. Inferring the paddings, margins, font sizes using trial and error takes a lot of time and I feel the process could become more efficient but not sure how to improve it. Using PSD files is not an option since buying Photoshop for each developer is currently not considered. Design guide is also not available since design is still evolving and new features are introduced. Ideas for improving the process above and sharing how the process looks like in your company will be great.

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• Name for Osherove's modified singleton pattern?

  - by Kazark

  I'm pretty well sold on the "singletons are evil" line of thought. Nevertheless, there are limited occurrences when you want to limit the creation of an object. Roy Osherove advises, If you're planning to use a singleton in your design, separate the logic of the singleton class and the logic that makes it a singleton (the part that initializes a static variables, for example) into two separate classes. That way, you can keep the single responsibility principle (SRP) and also have a way to override singleton logic. (The Art of Unit Testing 261-262) This pattern still perpetuates the global state. However, it does result in a testable design, so it seems to me to be a good pattern for mitigating the damage of a singleton. However, Osherove does not give a name to this pattern; but naming a pattern, according to the Gang of Four, is important: Naming a pattern immediately increases our design vocabulary. It lets us design at a higher level of abstraction. (3) Is there a standard name for this pattern? It seems different enough from a standard singleton to deserve a separate name. Decoupled Singleton, perhaps?

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• Advice on choosing a book to read

  - by Kioshiki

  I would like to ask for some recommendations on useful books to read. Initially I had intended on posting quite a long description of my current issue and asking for advice. But I realised that I didn’t have a clear idea of what I wanted to ask. One thing that is clear to me is that my knowledge in various areas needs improving and reading is one method of doing that. Though choosing the right book to read seems like a task in itself when there are so many books out there. I am a programmer but I also deal with analysis, design & testing. So I am not sure what type of book to read. One option might be to work through two books at the same time. I had thought maybe one about design or practices and another of a more technical focus. Recently I came across one book that I thought might be useful to read: http://xunitpatterns.com/index.html It seems like an interesting book, but the comments I read on amazon.co.uk show that the book is probably longer than it needs to be. Has anyone read it and can comment on this? Another book that I already own and would probably be a good one to finish reading is this: http://www.amazon.co.uk/Code-Complete-Practical-Handbook-Construction/dp/0735619670/ref=sr_1_1?ie=UTF8&qid=1309438553&sr=8-1 Has anyone else read this who can comment on its usefulness? Beyond these two I currently have no clear idea of what to read. I have thought about reading a book related to OO design or the GOF design patterns. But I wonder if I am worrying too much about the process and practices and not focusing on the actual work. I would be very grateful for any suggestions or comments. Many Thanks, Kioshiki

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• Relationship between SOA and OOA

  - by TheSilverBullet

  Thomas Erl defines SOA as follows in his site: Service-oriented computing represents a new generation distributed computing platform. As such, it encompasses many things, including its own design paradigm and design principles, design pattern catalogs, pattern languages, a distinct architectural model, and related concepts, technologies, and frameworks. This definitely sounds like a whole new category which is parallel to object orientation. Almost one in which you would expect an entirely new language to exist for. Like procedural C and object oriented C#. Here is my understanding: In real life, we don't have entirely new language for SOA. And most application which have SOA architecture have an object oriented design underneath it. SOA is a "strategy" to make the entire application/service distributed and reliable. SOA needs OOPS working underneath it. Is this correct? Where does SOA (if at all it does) fit in with object oriented programming practices? Edit: I have learnt through answers that OOA and SOA work with each other and cannot be compared (in a "which is better" way). I have changed the title to "Relationship between SOA and OOA" rather than "comparison".

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• Must all AI states be able to react to any event?

  - by Prog

  FSMs implemented with the State design pattern are a common way to design AI agents. I am familiar with the State design pattern and know how to implement it. How is this used in games to design AI agents? Consider a simplified class Monster, representing an AI agent: class Monster { State state; // other fields omitted public void update(){ // called every game-loop cycle state.execute(this); } public void setState(State state){ this.state = state; } // irrelevant stuff omitted } There are several State subclasses implementing execute() differently. So far, classic State pattern. AI agents are subject to environmental effects and other objects communicating with them. For example, an AI agent might tell another AI agent to attack (i.e. agent.attack()). Or a fireball might tell an AI agent to fall down. This means that the agent must have methods such as attack() and fallDown(), or commonly some message receiving mechanism to understand such messages. With an FSM, the current State of the agent should be the one taking care of such method calls - i.e. the agent delegates to the current state upon every event. Is this correct? If correct, how is this done? Are all states obligated by their superclass to implement methods such as attack(), fallDown() etc., so the agent can always delegate to them on almost every event? Or is it done in some other way?

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• How to learn to deliver quality software designs when working on a tight deadline?

  - by chester89

  I read many books about how to design great software, but I kind of struggle to come up with a good design decisions when it comes to business apps, especially when the timeframe is tough. In the company I currently work for, the following situation happen all the time: my teamlead tells me that there's a task to do, I call some guy or a girl from business who tells me exactly what is it they want, and then I start coding. The task always fits in some existing application (we do only web apps or web services), usually it's purpose is to pull data from one datasource and put into the other one, with some business logic attached in the process. I start coding and then, after spending some time on a problem, my code didn't work as expected - either because of technical mistake or my lack of knowledge of the domain. The business is ringing me 2-3 times a day to hurry me up. I ask my team lead to help, he comes up, sees my code and goes like 'What's this?'. Then he throws away about half of my code, including all the design decisions I made, writes 2-3 methods that does the job (each of them usually 200-300 lines long or more, by the way), and task is complete, code works as it should have. The guy is smarter than me, obviously, and I'm aware of that. My goal is to be better software developer, that means write better code, not finish the job quicker with some crappy code. And the thing is, when I have enough time to tackle a problem, I can come up with a design that is good (in my opinion, of course), but I fall short to do so when I'm on a tight deadline. What should I do? I am fully aware that it's rather vague explanation, but please bear with me

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• How useful are design patterns when it comes to web programming?

  - by Raja

  Background: My organization uses Microsoft .Net (3.5) with SQL Server 2005 as back end. With RAD being the norm and Agile being the widely used process. I have always found using design patterns difficult since it involves a bit more understanding and bit more training. Can you give me some examples where design patterns have solved real time problems in Web programming? What is the criteria for using any design pattern? What is the benefit reaped from it. I know it is a general question but this would help me a bunch.

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• Flash Web Design with the Help of Flash Professionals

  Flash has often been criticized by web specialists for its relatively slow loading time. It?s also been targeted by many people who have experienced loading problem of a Flash site on the web. But no... [Author: David Jackson - Web Design and Development - August 31, 2009]

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• 24 Hours of PASS – Database Design Fundamentals

  - by drsql

  Well, I have to admit when I got the invite to speak during this event, I was honored (and still am for that matter). But I have to admit, I hope people don’t come in with any belief that I will be Celebrating SQL Server 2008 R2.  Most of what I will present could have been celebrated with SQL Server 6.5, as I will be doing my bread and butter Database Design Fundamentals session that I have done multiple times over the past few years. Ironically, had the people that you and I work with/for...(read more)

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• Professional Custom Logo Design vs. Mr. Right

  John is an ex-marine and ex-employee of general motors. He recently lost his job working as a welder on the assembly lines of one of GM manufacturing plants. John has traveled a lot and knows a lot a... [Author: Emily Matthew - Web Design and Development - March 31, 2010]

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• Design Book– Third Section (Implementing the Database)

  - by drsql

  The third section is the primary section that a person who has some decent knowledge and experience doing design will likely really find exciting. Whereas the first half of the book is there for fundamentals, this section is more skills based, and unless you are a walking encyclopedia of SQL Server syntax (and I am not), you have to use some form of reference to discover how to implement different sorts of problems using DDL, including Triggers, Constraints, etc;  Security; Source Control, etc....(read more)

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• Website Design Versus Website Development

  Even though website design and website development is treated as one and the same thing, one should not confuse the differences between the two. To make a website complete, both a website designer and developers contribution is important as without either one we would not be able to view the websites on the world wide web.

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• Google I/O 2011: Smart App Design

  Google I/O 2011: Smart App Design Travis Green, Max Lin, Robert Kaplow, Jóhannes Kristinsson, Ryan McGee Learn how to recommend the unexpected, automate the repetitive, and distill the essential using machine learning. This session will show you how you can easily add smarts to your apps with the Prediction API, and how to create apps that rapidly adapt to new data. From: GoogleDevelopers Views: 10078 47 ratings Time: 01:01:04 More in Science & Technology

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• Power, Cooling and Data Center Design -- From Square One

  Building a data center from scratch doesn't just mean getting the latest in gear. It also brings with it the latest power, cooling and data center design. Here's what one company did.

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• Power, Cooling and Data Center Design -- From Square One

  Building a data center from scratch doesn't just mean getting the latest in gear. It also brings with it the latest power, cooling and data center design. Here's what one company did.

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