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  • So what *did* Alan Kay really mean by the term "object-oriented"?

    - by Charlie Flowers
    Reportedly, Alan Kay is the inventor of the term "object oriented". And he is often quoted as having said that what we call OO today is not what he meant. For example, I just found this on Google: "I made up the term 'object-oriented', and I can tell you I didn't have C++ in mind" - Alan Kay, OOPSLA '97 I vaguely remember hearing something pretty insightful about what he did mean. Something along the lines of "message passing". Do you know what he meant? Can you fill in more details of what he meant and how it differs from today's common OO? Please share some references if you have any. Thanks.

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  • 15 Stylish Navigation Menus For Inspiration

    - by Jyoti
    A site’s navigation menu is one of the most prominent things that users see when they first visit. There are many ways to design a navigation menu  and since almost all websites have some form of navigation designers have to push their creative limits to build one that’s remarkable and outstanding. In this article, you’ll [...]

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  • How does I/O work for large graph databases?

    - by tjb1982
    I should preface this by saying that I'm mostly a front end web developer, trained as a musician, but over the past few years I've been getting more and more into computer science. So one idea I have as a fun toy project to learn about data structures and C programming was to design and implement my own very simple database that would manage an adjacency list of posts. I don't want SQL (maybe I'll do my own query language? I'm just having fun). It should support ACID. It should be capable of storing 1TB let's say. So with that, I was trying to think of how a database even stores data, without regard to data structures necessarily. I'm working on linux, and I've read that in that world "everything is a file," including hardware (like /dev/*), so I think that that obviously has to apply to a database, too, and it clearly does--whether it's MySQL or PostgreSQL or Neo4j, the database itself is a collection of files you can see in the filesystem. That said, there would come a point in scale where loading the entire database into primary memory just wouldn't work, so it doesn't make sense to design it with that mindset (I assume). However, reading from secondary memory would be much slower and regardless some portion of the database has to be in primary memory in order for you to be able to do anything with it. I read this post: Why use a database instead of just saving your data to disk? And I found it difficult to understand how other databases, like SQLite or Neo4j, read and write from secondary memory and are still very fast (faster, it would seem, than simply writing files to the filesystem as the above question suggests). It seems the key is indexing. But even indexes need to be stored in secondary memory. They are inherently smaller than the database itself, but indexes in a very large database might be prohibitively large, too. So my question is how is I/O generally done with large databases like the one I described above that would be at least 1TB storing a big adjacency list? If indexing is more or less the answer, how exactly does indexing work--what data structures should be involved?

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  • Is pixelmator a viable alternative for photoshop? [migrated]

    - by ChrisR
    I've always been a photoshop user, i know the ins and outs and know my way around all the tools i need for my webdesign work. But now i'm faced with a dilemma, for my new job i haven't got the budget for a full photoshop license so i'm wondering, is pixelmator a good alternative? I use Photoshop mainly to slice a design into separate images so enable/disable layers is a must, PSD compatibility too, ... Anyone has experience with Pixelmator?

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  • What is a Non-Functional Requirement?

    - by atconway
    In my breakdown of work I have to define work against 'Functional' and 'Non-Functional' design elements / work in my applications. I read the description from Wikipedia here: https://en.wikipedia.org/wiki/Non-functional_requirement but as typical the description did not speak exactly to me to clear up my understanding. Can someone please explain in terms of an example when creating an application from scratch, what would be defined as a 'Non-Functional' requirement?

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  • Advantages and disadvantages of building a single page web application

    - by ryanzec
    I'm nearing the end of a prototyping/proof of concept phase for a side project I'm working on, and trying to decide on some larger scale application design decisions. The app is a project management system tailored more towards the agile development process. One of the decisions I need to make is whether or not to go with a traditional multi-page application or a single page application. Currently my prototype is a traditional multi-page setup, however I have been looking at backbone.js to clean up and apply some structure to my Javascript (jQuery) code. It seems like while backbone.js can be used in multi-page applications, it shines more with single page applications. I am trying to come up with a list of advantages and disadvantages of using a single page application design approach. So far I have: Advantages All data has to be available via some sort of API - this is a big advantage for my use case as I want to have an API to my application anyway. Right now about 60-70% of my calls to get/update data are done through a REST API. Doing a single page application will allow me to better test my REST API since the application itself will use it. It also means that as the application grows, the API itself will grow since that is what the application uses; no need to maintain the API as an add-on to the application. More responsive application - since all data loaded after the initial page is kept to a minimum and transmitted in a compact format (like JSON), data requests should generally be faster, and the server will do slightly less processing. Disadvantages Duplication of code - for example, model code. I am going to have to create models both on the server side (PHP in this case) and the client side in Javascript. Business logic in Javascript - I can't give any concrete examples on why this would be bad but it just doesn't feel right to me having business logic in Javascript that anyone can read. Javascript memory leaks - since the page never reloads, Javascript memory leaks can happen, and I would not even know where to begin to debug them. There are also other things that are kind of double edged swords. For example, with single page applications, the data processed for each request can be a lot less since the application will be asking for the minimum data it needs for the particular request, however it also means that there could be a lot more small request to the server. I'm not sure if that is a good or bad thing. What are some of the advantages and disadvantages of single page web applications that I should keep in mind when deciding which way I should go for my project?

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  • What are the advantages of the delegate pattern over the observer pattern?

    - by JoJo
    In the delegate pattern, only one object can directly listen to another object's events. In the observer pattern, any number of objects can listen to a particular object's events. When designing a class that needs to notify other object(s) of events, why would you ever use the delegate pattern over the observer pattern? I see the observer pattern as more flexible. You may only have one observer now, but a future design may require multiple observers.

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  • What advantages do we have when creating a separate mapping table for two relational tables

    - by Pankaj Upadhyay
    In various open source CMS, I have noticed that there is a separate table for mapping two relational tables. Like for categories and products, there is a separate product_category_mapping table. This table just has a primary key and two foreign keys from the categories and product tables. My question is what are the benefits of this database design rather than just linking the tables directly by defining a foreign key in either table? Is it just matter of convenience?

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  • Single Responsibility Principle Implementation

    - by Mike S
    In my spare time, I've been designing a CMS in order to learn more about actual software design and architecture, etc. Going through the SOLID principles, I already notice that ideas like "MVC", "DRY", and "KISS", pretty much fall right into place. That said, I'm still having problems deciding if one of two implementations is the best choice when it comes to the Single Responsibility Principle. Implementation #1: class User getName getPassword getEmail // etc... class UserManager create read update delete class Session start stop class Login main class Logout main class Register main The idea behind this implementation is that all user-based actions are separated out into different classes (creating a possible case of the aptly-named Ravioli Code), but following the SRP to a "tee", almost literally. But then I thought that it was a bit much, and came up with this next implementation class UserView extends View getLogin //Returns the html for the login screen getShortLogin //Returns the html for an inline login bar getLogout //Returns the html for a logout button getRegister //Returns the html for a register page // etc... as needed class UserModel extends DataModel implements IDataModel // Implements no new methods yet, outside of the interface methods // Haven't figured out anything special to go here at the moment // All CRUD operations are handled by DataModel // through methods implemented by the interface class UserControl extends Control implements IControl login logout register startSession stopSession class User extends DataObject getName getPassword getEmail // etc... This is obviously still very organized, and still very "single responsibility". The User class is a data object that I can manipulate data on and then pass to the UserModel to save it to the database. All the user data rendering (what the user will see) is handled by UserView and it's methods, and all the user actions are in one space in UserControl (plus some automated stuff required by the CMS to keep a user logged in or to ensure that they stay out.) I personally can't think of anything wrong with this implementation either. In my personal feelings I feel that both are effectively correct, but I can't decide which one would be easier to maintain and extend as life goes on (despite leaning towards Implementation #1.) So what about you guys? What are your opinions on this? Which one is better? What basics (or otherwise, nuances) of that principle have I missed in either design?

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  • How can I solve the same problems a CB-architecture is trying to solve without using hacks? [on hold]

    - by Jefffrey
    A component based system's goal is to solve the problems that derives from inheritance: for example the fact that some parts of the code (that are called components) are reused by very different classes that, hypothetically, would lie in a very different branch of the inheritance tree. That's a very nice concept, but I've found out that CBS is often hard to accomplish without using ugly hacks. Implementations of this system are often far from clean. But I don't want to discuss this any further. My question is: how can I solve the same problems a CBS try to solve with a very clean interface? (possibly with examples, there are a lot of abstract talks about the "perfect" design already). Here's an example I was going for before realizing I was just reinventing inheritance again: class Human { public: Position position; Movement movement; Sprite sprite; // other human specific components }; class Zombie { Position position; Movement movement; Sprite sprite; // other zombie specific components }; After writing that I realized I needed an interface, otherwise I would have needed N containers for N different types of objects (or to use boost::variant to gather them all together). So I've thought of polymorphism (move what systems do in a CBS design into class specific functions): class Entity { public: virtual void on_event(Event) {} // not pure virtual on purpose virtual void on_update(World) {} virtual void on_draw(Window) {} }; class Human { private: Position position; Movement movement; Sprite sprite; public: virtual void on_event(Event) { ... } virtual void on_update(World) { ... } virtual void on_draw(Window) { ... } }; class Zombie { private: Position position; Movement movement; Sprite sprite; public: virtual void on_event(Event) { ... } virtual void on_update(World) { ... } virtual void on_draw(Window) { ... } }; Which was nice, except for the fact that now the outside world would not even be able to know where a Human is positioned (it does not have access to its position member). That would be useful to track the player position for collision detection or if on_update the Zombie would want to track down its nearest human to move towards him. So I added const Position& get_position() const; to both the Zombie and Human classes. And then I realized that both functionality were shared, so it should have gone to the common base class: Entity. Do you notice anything? Yes, with that methodology I would have a god Entity class full of common functionality (which is the thing I was trying to avoid in the first place).

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  • Designing Videogame Character Parodies [duplicate]

    - by David Dimalanta
    This question already has an answer here: Is it legal to add a cameo appearance of a known video game character in my game? 2 answers Was it okay to make a playable character when making a videogame despite its resemblance? For example, I'm making a 3rd-person action-platform genre and I have to make a character design resembling like Megaman but not exactly the same as him since there is little alternate in color, details, and facial features.

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  • What's the problem with Scala's XML literals?

    - by Oak
    In this post, Martin (the language's head honcho) writes: [XML literals] Seemed a great idea at the time, now it sticks out like a sore thumb. I believe with the new string interpolation scheme we will be able to put all of XML processing in the libraries, which should be a big win. Being interested in language design myself, I'm wondering: Why does he write that it was a mistake to incorporate XML literals into the language? What is the controversy regarding this feature?

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  • "UML is the worst thing to ever happen to MDD." Why?

    - by Florents
    William Cook in a tweet wrote that: "UML is the worst thing to ever happen to MDD. Fortunately many people now realize this ..." I would like to know the reasoning behind that claim (apparently, I'm not referring to his personal opinion). I've noticed that many people out there don't like UML that much. Also it is worth mentioning that he is in academia, where UML is preety much the holy grail of effective design and modelling.

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  • SQL: empty string vs NULL value

    - by Jacek Prucia
    I know this subject is a bit controversial and there are a lot of various articles/opinions floating around the internet. Unfortunatelly, most of them assume the person doesn't know what the difference between NULL and empty string is. So they tell stories about surprising results with joins/aggregates and generally do a bit more advanced SQL lessons. By doing this, they absolutely miss the whole point and are therefore useless for me. So hopefully this question and all answers will move subject a bit forward. Let's suppose I have a table with personal information (name, birth, etc) where one of the columns is an email address with varchar type. We assume that for some reason some people might not want to provide an email address. When inserting such data (without email) into the table, there are two available choices: set cell to NULL or set it to empty string (''). Let's assume that I'm aware of all the technical implications of choosing one solution over another and I can create correct SQL queries for either scenario. The problem is even when both values differ on the technical level, they are exactly the same on logical level. After looking at NULL and '' I came to a single conclusion: I don't know email address of the guy. Also no matter how hard i tried, I was not able to sent an e-mail using either NULL or empty string, so apparently most SMTP servers out there agree with my logic. So i tend to use NULL where i don't know the value and consider empty string a bad thing. After some intense discussions with colleagues i came with two questions: am I right in assuming that using empty string for an unknown value is causing a database to "lie" about the facts? To be more precise: using SQL's idea of what is value and what is not, I might come to conclusion: we have e-mail address, just by finding out it is not null. But then later on, when trying to send e-mail I'll come to contradictory conclusion: no, we don't have e-mail address, that @!#$ Database must have been lying! Is there any logical scenario in which an empty string '' could be such a good carrier of important information (besides value and no value), which would be troublesome/inefficient to store by any other way (like additional column). I've seen many posts claiming that sometimes it's good to use empty string along with real values and NULLs, but so far haven't seen a scenario that would be logical (in terms of SQL/DB design). P.S. Some people will be tempted to answer, that it is just a matter of personal taste. I don't agree. To me it is a design decision with important consequences. So i'd like to see answers where opion about this is backed by some logical and/or technical reasons.

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  • What are DRY, KISS, SOLID, etc. classified as?

    - by Morgan Herlocker
    Is something like DRY a design pattern, a methodology, or something in between? They do not have specific implementations that could neccessarily be demonstrated(even if you can easily demonstrate a case NOT using something like KISS... see The Daily WTF for a plethora of examples), nor do they fully explain a development process like a methodology generally would. Where does that leave these types of "rule of thumb"'s?

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  • What are the essential things one needs to know about UML?

    - by Hanno Fietz
    I want my scribbles of a program's design and behaviour to become more streamlined and have a common language with other developers. I looked at UML and in principle it seems to be what I'm looking for, but it seems to be overkill. The information I found online also seems very bloated and academic. How can I understand UML in plain-English way, enough to be able to explain it to my colleagues? What are the canonical resources for understanding UML at a ground level?

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  • Starting all over again?

    - by kyndigs
    Have you ever been developing something and just came to a point where you think that this is rubbish, the design is bad and although I will lose time it will be better to just start all over again? What should you consider before making this step? I know it can be drastic in some cases, is it best to just totally ignore what you did before, or take some of the best bits from it? Some real life examples would be great.

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  • What's the most useful 10% of UML and is there a quick tutorial on it?

    - by Hanno Fietz
    I want my scribbles of a program's design and behaviour to become more streamlined and have a common language with other developers. I looked at UML and in principle it seems to be what I'm looking for, just way overkill. The information I found online also seems very bloated and academic. Is there a no-bullshit, 15-minutes introduction to the handful of UML symbols I'll need when discussing the architecture of some garden variety software on a whiteboard with my colleagues?

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  • Should I use multiple column primary keys or add a new colum?

    - by Covar
    My current database design makes use of a multiple column primary key to use existing data (that would be unique anyway) instead of creating an additional column assigning each entry an arbitrary key. I know that this is allowed, but was wondering if this is a practice that I might want to use cautiously and possibly avoid (much like goto in C). So what are some of the disadvantages I might see in this approach or reasons I might want a single column key?

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  • How can I improve my skills while working on actual projects, in the absence of more experienced developers?

    - by LolCoder
    I'm the lead developer at a small company, working with C# and ASP.Net. Our team is small, 2-3 people, without much experience in development and design. I don't have the opportunity to learn from more senior developers, there is no one in my team to guide me and help me choose the best approaches, as I take care most of the projects myself. How can I improve my software development skills while working on actual projects, in the absence of more experienced developers?

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  • Attaching new animations onto skeleton via props, a good idea?

    - by Cardin
    I'm thinking of coding a game with an idea of mine. I've coded 2D games before, but I'm new to 3D programming, so I'd like to ask if this idea of mine is feasible or out of my depth. I'm making a game where there are many different characters for the player to choose from (JRPG style). So to save time, I have an idea of creating many different varied characters using a completely naked body mesh and animation skeleton, standardised across all characters. For example, by placing different hair, boots, armor props on the character mesh, new characters can be formed. Kinda like playing dress-up with a barbie doll. I'm thinking this can be done by having a bone on the prop that I can programmically attach to the main mesh. Also, I plan to have some props add new animations to the base skeleton, so equipping some particular props would give it new attack, damage, idle animations. This is because I can't expect the character to have the same swinging animation if he had a big sword or an axe. I think this might be possible if the prop has its own instance of the animation skeleton with just only the new animations, and parenting the base body mesh to this new skeleton. So all the base body mesh has are just the basic animations, other animations come from the props. My concerns are, 1) the props might not attach to the mesh properly and jitter a lot, 2) since prop and body are animated differently, the props and base mesh will cause visual artefacts, like the naked thighs showing through the pants when the character walks, 3) a custom pipeline have to be developed to export skeletons without mesh, and also to attach the base body mesh to a new skeleton during runtime in the game. So my question: are these features considered 'easy' to code? Or am I trying to do something few have ever succeeded with on their own? It feels like all these can be done given enough time and I know I definitely have to do a bit of bone matrix calculations, but I really don't want to drag out the development timeline unnecessarily from coding mathematically intense things or analyzing how to parse 3D export formats. I'm currently only at the Game Design stage, so if these features aren't a good idea, I can simply change the design of the game. (Unrelated to question) I could always, as last resort, have the characters have predetermined outfit and weapon selections so as to animate everything manually.

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  • self referencing tables, good or bad?

    - by NimChimpsky
    Representing geographical locations within an application, the design of the underlying data model suggests two clear options (or maybe more?). One table with a self referencing parent_id column uk - london (london parent id = UK id) or two tables, with a one to many relationship using a foreign key. My preference is for one self-refercing table as it easily allows to extend into as many sub regions as required. IN general do people veer away from self referencing tables, or are they A-OK ?

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  • iOS - Unit tests for KVO/delegate codes

    - by ZhangChn
    I am going to design a MVC pattern. It could be either designed as a delegate pattern, or a Key-Value-Observing(KVO), to notify the controller about changing models. The project requires certain quality control procedures to conform to those verification documents. My questions: Does delegate pattern fit better for unit testing than KVO? If KVO fits better, would you please suggest some sample codes?

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  • Interaction of a GUI-based App and Windows Service

    - by psubsee2003
    I am working on personal project that will be designed to help manage my media library, specifically recordings created by Windows Media Center. So I am going to have the following parts to this application: A Windows Service that monitors the recording folder. Once a new recording is completed that meets specific criteria, it will call several 3rd party CLI Applications to remove the commercials and re-encode the video into a more hard-drive friendly format. A controller GUI to be able to modify settings of the service, specifically add new shows to watch for, and to modify parameters for the CLI Applications A standalone (GUI-based) desktop application that can perform many of the same functions as the windows service, expect manually on specific files instead of automatically based on specific criteria. (It should be mentioned that I have limited experience with an application of this complexity, and I have absolutely zero experience with Windows Services) Since the 1st and 3rd bullet share similar functionality, my design plan is to pull the common functionality into a separate library shared by both parts applications, but these 2 components do not need to interact otherwise. The 2nd and 3rd bullets seem to share some common functionality, both will have a GUI, both will have to help define similar parameters (one to send to the service and the other to send directly to the CLI applications), so I can see some advantage to combining them into the same application. On the other hand, the standalone application (bullet #3) really does not need to interact with the service at all, except for possibly sharing a few common default parameters that can easily be put into an XML in a common location, so it seems to make more sense to just keep everything separate. The controller GUI (2nd bullet) is where I am stuck at the moment. Do I just roll this functionality (allow for user interaction with the service to update settings and criteria) into the standalone application? Or would it be a better design decision to keep them separate? Specifically, I'm worried about adding the complexity of communicating with the Windows Service to the standalone application when it doesn't need it. Is WCF the right approach to allow the controller GUI to interact with the Windows Service? Or is there a better alternative? At the moment, I don't envision a need for a significant amount of interaction, maybe just adding a new task once in a while and occasionally tweaking a parameter, but when something is changed, I do expect the windows service to immediately use the new settings.

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