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• Adventures in the Land of CloudDB/NoSQL/NoAcid

  - by KKline

  Cloud, Bunny, or CloudBunny? Last year, some of my friends from Quest Software attended Hadoop World in New York. In 2009, I never would've guessed that Quest would be there with products, community initiatives, as a major sponsor and with presenters? There were just under 1,000 attendees who weren’t the typical devheads and geekasaurs you'd normally see at very techie events like Code Camps, SQL Saturdays, Cloud Camps and or even other NoSQL events such as the Cassandra Summit. We're talkin' enterprise...(read more)

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• Can an aggregate root hold references of members of another aggregate root?

  - by Rushino

  Hello, I know outside aggregates cant change anything inside an aggregate without passing by his root. That said i would like to know if an aggregate root can hold references of members (objects insides) of another aggregate root? (fellowing DDD rules) Example : a Calendar contain a list of phases which contain a list of sequences which contain a list of assignations Calendar is root because phases and sequences and assignations only work in context of a calendar. You also have Students and Groups of student (called groups) It is possible (fellowing DDD rules) to make Groups holding references of assignations or it need to pass by the root for accessing groups from assignations ? Thanks.

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• What is the value in hiding the details through abstractions? Isn't there value in transparency?

  - by user606723

  Background I am not a big fan of abstraction. I will admit that one can benefit from adaptability, portability and re-usability of interfaces etc. There is real benefit there, and I don't wish to question that, so let's ignore it. There is the other major "benefit" of abstraction, which is to hide implementation logic and details from users of this abstraction. The argument is that you don't need to know the details, and that one should concentrate on their own logic at this point. Makes sense in theory. However, whenever I've been maintaining large enterprise applications, I always need to know more details. It becomes a huge hassle digging deeper and deeper into the abstraction at every turn just to find out exactly what something does; i.e. having to do "open declaration" about 12 times before finding the stored procedure used. This 'hide the details' mentality seems to just get in the way. I'm always wishing for more transparent interfaces and less abstraction. I can read high level source code and know what it does, but I'll never know how it does it, when how it does it, is what I really need to know. What's going on here? Has every system I've ever worked on just been badly designed (from this perspective at least)? My philosophy When I develop software, I feel like I try to follow a philosophy I feel is closely related to the ArchLinux philosophy: Arch Linux retains the inherent complexities of a GNU/Linux system, while keeping them well organized and transparent. Arch Linux developers and users believe that trying to hide the complexities of a system actually results in an even more complex system, and is therefore to be avoided. And therefore, I never try to hide complexity of my software behind abstraction layers. I try to abuse abstraction, not become a slave to it. Question at heart Is there real value in hiding the details? Aren't we sacrificing transparency? Isn't this transparency valuable?

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• Multithreaded UI desktop application issues

  - by igor

  I am involved into development a rich UI project: desktop windows application. Application uses asynchronous invocations and in its turn it should be ready to process external messages (events). The problem is clear: at first time it was built as a simple prototype and it was not stress tested and all was fine. Then application was grown: the number of calls to server and number of events from server are high and performance is low. What is more users noticed that sometimes performance is extremal low. Asynchronous invocations based on thread pool (BeginInvoke, EndInvoke), external events are going from WCF service (.NET 3.5). My goal is synchronization of all tasks and putting priorities to every executions in desktop application. My question is: is there any practice how to reach my goal: patterns, task priority list, others? What should I do at first, second and next times? Thanks

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• What are current Biggest Challenges faced by Ecommerce Applications ?

  - by Rachel

  I am in the process to start Product Development for E-commerce and Online Retail domain but before starting I would like to know what are the biggest challenges faced by current state of Art E-Commerce Application ? Also I have not experience building e-commerce products and so what things should I keep in mind before developing one ? Is there are books, articles, blogs outside which I should refer to gain some knowledge before starting out ? Update: What are you thoughts on the recommendation engines for ecommerce applications ? What challenges we have with current state of recommendations engines for ecommerce web application and how can we overcome them ?

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• In retrospect, has it been a good idea to use three-valued logic for SQL NULL comparisons?

  - by Heinzi

  In SQL, NULL means "unknown value". Thus, every comparison with NULL yields NULL (unknown) rather than TRUE or FALSE. From a conceptional point of view, this three-valued logic makes sense. From a practical point of view, every learner of SQL has, one time or another, made the classic WHERE myField = NULL mistake or learned the hard way that NOT IN does not do what one would expect when NULL values are present. It is my impression (please correct me if I am wrong) that the cases where this three-valued logic helps (e.g. WHERE myField IS NOT NULL AND myField <> 2 can be shortened to WHERE myField <> 2) are rare and, in those cases, people tend to use the longer version anyway for clarity, just like you would add a comment when using a clever, non-obvious hack. Is there some obvious advantage that I am missing? Or is there a general consensus among the development community that this has been a mistake?

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• Using IComparable<T> Interface

  - by Pawan_Mishra

  Level : Beginner to Intermediate C# language has constantly evolved over a constant period of time.Each new version introduced new features which changed the way we programmed and solved the problems. Whether it was introduction of generics in C# 2.0 , LINQ in C# 3.0 or concept of dynamic programming in C# 4.0 , each of them had or will have greater impact on our programming style.As a developer we don’t have much option but to evolve and redefine our self in this constantly changing environment...(read more)

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• C# XNA - Sky Sphere Question

  - by Wade

  I have been banging my head against the wall trying to get a sky sphere to work appropriately in XNA 4.0. I have the sphere loading correctly, and even textured, but i would like something a little more dynamic that can support a day/night cycle. My issue is that, while i know a good amount of C# and XNA, i know next to nothing about HLSL. (I could make an ambient light shader if my life depended on it...) I also have not been able to find a tutorial on how to build a sky sphere like this. Of course i don't expect to be able to make an amazing one right off the bat, i would like to start small, with a dynamic coloring sky i'll work out the clouds and sun later. My first question: Does anyone know of any good tutorial sites that could help me get a decent grasp around HLSL? Second: Does anyone have a good example of or know where to find one of a gradient sky using XNA and C#?

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• Dapper and object validation/business rules enforcement

  - by Eugene

  This isn't really Dapper-specific, actually, as it relates to any XML-serializeable object.. but it came up when I was storing an object using Dapper. Anyways, say I have a user class. Normally, I'd do something like this: class User { public string SIN {get; private set;} public string DisplayName {get;set;} public User(string sin) { if (string.IsNullOrWhiteSpace(sin)) throw new ArgumentException("SIN must be specified"); this.SIN = sin; } } Since a SIN is required, I'd just create a constructor with a sin parameter, and make it read-only. However, with a Dapper (and probably any other ORM), I need to provide a parameterless constructor, and make all properties writeable. So now I have this: class User: IValidatableObject { public int Id { get; set; } public string SIN { get; set; } public string DisplayName { get; set; } public IEnumerable<ValidationResult> Validate(ValidationContext validationContext) { // implementation } } This seems.. can't really pick the word, a bad smell? A) I'm allowing to change properties that should not be changed ever after an object has been created (SIN, userid) B) Now I have to implement IValidatableObject or something like that to test those properties before updating them to db. So how do you go about it ?

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• Configuration data: single-row table vs. name-value-pair table

  - by Heinzi

  Let's say you write an application that can be configured by the user. For storing this "configuration data" into a database, two patterns are commonly used. The single-row table CompanyName | StartFullScreen | RefreshSeconds | ... ---------------+-------------------+------------------+-------- ACME Inc. | true | 20 | ... The name-value-pair table ConfigOption | Value -----------------+------------- CompanyName | ACME Inc. StartFullScreen | true (or 1, or Y, ...) RefreshSeconds | 20 ... | ... I've seen both options in the wild, and both have obvious advantages and disadvantages, for example: The single-row tables limits the number of configuration options you can have (since the number of columns in a row is usually limited). Every additional configuration option requires a DB schema change. In a name-value-pair table everything is "stringly typed" (you have to encode/decode your Boolean/Date/etc. parameters). (many more) Is there some consensus within the development community about which option is preferable?

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• Beginning with first project on game development [closed]

  - by Tsvetan

  Today is the day I am going to start my first real game project. It will be a Universe simulator. Basically, you can build anything from tiny meteor to quazars and universes. It is going to be my project for an olympiad in IT in my country and I really want to make it perfect(at least a bronze medal). So, I would like to ask some questions about organization and development methodologies. Firstly, my plan is to make a time schedule. In it I would write my plans for the next month or two(because that is the time I have). With this exact plan I hope to make my organisation at its best. Of course, if I am doing sth faster than the schedule I would involve more features for the game and/or continue with the tempo I have. Also, for the organisation I would make a basic pseudocode(maybe) and just rewrite it so it is compilable. Like a basic skeleton of everything. The last is an idea I tought of in the moment, but if it is good I will use it. Secondly, for the development methodologies, obviously, I think of making object-oriented code and make everything perfect(a lot of testing, good code, documentation etc.). Also, I am going to make my own menu system(I read that OpenGL hasn't got very good one). Maybe I would implement it with an xml file, holding the info about position of buttons, text boxes, images and everything. Maybe I would do a specific CSS for it and so on. I think that is very good way of doing the menu system, because it makes the presentation layer separate of the logic. But, if there is a better way, I would do it the better way. For the logic, well, I don't have much to say. OO code, testing, debuging, good and fast algorithms and so on. Also, a good documentation must be written and this is the area I need to make some research in. I think that is for now. I hope I have been enough descriptive. If more questions come on my mind, I will ask them. Edit: I think of blogging every part of the project, or at least writing down everything in a file or something like that. My question is: Is my plan of how to do everything around the project good? And if not, what is necessary to be improved and what other things I can involve for making the project good.

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• Scene Graph Traversing Techniques

  - by Bunkai.Satori

  Scene Graph seems to be the most effective way of representing the game world. The game world usually tends to be as large as the memory and device can handle. In contrast, the screen of the device captures only a fraction of the Game World/Scene Graph. Ideally, I wish to process(update and render) only the visible game objects/nodes on per-frame basis. My question therefore is, how to traverse the scene graph so, that I will focus only on the game notes that are in the camera frustum? How to organize data so that I can easily focus only on the scene graph nodes visible to me? What are techniques to minimize scenegraph traversal time? Is there such way as more effective traversal, or do I have to traverse whole scene graph on per-frame basis?

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• What's wrong with JavaScript

  - by ts01

  There is a lot of buzz around Dart recently, often questioning Google motivations and utility of Dart as replacement for JavaScript. I was searching for rationale of creating Dart rather than investing more effort in ECMAScript. In well known leaked mail its author is saying that Javascript has historical baggage that cannot be solved without a clean break. But there is only one concrete example given (apart of performance concerns) of "fundamental language problems", which is an existence of a single Number primitive So, my questions are: How an existence of a single Number primitive can be a "fundamental problem"? Are there other known "fundamental problems" in JavaScript?

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• Designing a large database with multiple sources

  - by CatchingMonkey

  I have been tasked with redesigning, or at worst optimising the structure of a database for a data warehouse. Currently, the database has 4 other source databases (which is due to expand to X number of others), all of which have their own data structures, naming conventions etc. At the moment an overnight SSIS package pulls the data from the various source and then for each source coverts the data into a standardised, usable format. These tables are then appended to each other creating a 60m row, 40 column beast!. This table is then used in a variety of ways from an OLAP cube to a web front end. The structure has been in place for a very long time, and the work I have been able to prove the advantages of normalisation, and this is the way I would like to go. The problem for me is that the overnight process takes so long I don't then want to spend additional time normalising the last table into something usable. Can anyone offer any insight or ideas into the best way to restructure or optimise the database efficiently? Edit: All the databases are MS SQL Server 2008 R2 Thanks in advance CM

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• Factors to consider when building an algorithm for gun recoil

  - by Nate Bross

  What would be a good algorithm for calculating the recoil of a shooting guns cross-hairs? What I've got now, is something like this: Define min/max recoil based on weapon size Generate random number of "delta" movement Apply random value to X, Y, or both of cross-hairs (only "up" on the Y axis) Multiply new delta based on time from the previous shot (more recoil for full-auto) What I'm worried about is that this feels rather predicable, what other factors should one take into account when building recoil? While I'd like it to be somewhat predictable, I'd also like to keep players on their toes. I'm thinking about increasing the min/max recoil values by a large amount (relatively) and adding a weighting, so large recoils will be more rare -- it seems like a lot of effort to go into something I felt would be simple. Maybe this is just something that needs to be fine-tuned with additional playtesting, and more playtesters? I think that it's important to note, that the recoil will be a large part of the game, and is a key factor in the game being fun/challenging or not.

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• Advantages of Singleton Class over Static Class?

  Point 1)Singleton We can get the object of singleton and then pass to other methods.Static Class We can not pass static class to other methods as we pass objectsPoint 2) Singleton In future, it is easy to change the logic of of creating objects to some pooling mechanism. Static Class Very difficult to implement some pooling logic in case of static class. We would need to make that class as non-static and then make all the methods non-static methods, So entire your code needs to be changed.Point3:) Singleton Can Singletone class be inherited to subclass? Singleton class does not say any restriction of Inheritence. So we should be able to do this as long as subclass is also inheritence.There's nothing fundamentally wrong with subclassing a class that is intended to be a singleton. There are many reasons you might want to do it. and there are many ways to accomplish it. It depends on language you use.Static Class We can not inherit Static class to another Static class in C#. Think about it this way: you access static members via type name, like this: MyStaticType.MyStaticMember(); Were you to inherit from that class, you would have to access it via the new type name: MyNewType.MyStaticMember(); Thus, the new item bears no relationships to the original when used in code. There would be no way to take advantage of any inheritance relationship for things like polymorphism. span.fullpost {display:none;}

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• How to document/verify consistent layering?

  - by Morten

  I have recently moved to the dark side: I am now a CUSTOMER of software development -- mainly websites. With this new role comes new concerns. As a programmer i know how solid an application becomes when it is properly layered, and I want to use this knowledge in my new job. I don't want business logic in my presentation layer, and certainly not presentation stuff in my data layer. Thus, I want to be able to demand from my supllier that they document the level of layering, and how neat and consistent the layering is. The big question is: How is the level of layering documented to me as a customer, and is that a reasonable demmand for me to have, so I don't have to look in the code (I'm not supposed to do that anymore)?

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• Multithreded UI desktop application issues

  - by igor

  I am involved into development a rich UI project: desktop windows application. Application uses asynchronous invocations and in its turn it should be ready to process external messages (events). The problem is clear: at first time it was built as a simple prototype and it was not stress tested and all was fine. Then application was grown: the number of calls to server and number of events from server are high and performance is low. What is more users noticed that sometimes performance is extremal low. Asynchronous invocations based on thread pool (BeginInvoke, EndInvoke), external events are going from WCF service (.NET 3.5). My goal is synchronization of all tasks and putting priorities to every executions in desktop application. My question is: is there any practice how to reach my goal: patterns, task priority list, others? What should I do at first, second and next times? Thanks

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• What are the downsides to using dependency injection?

  - by kerry

  I recently came across an interesting question on stack overflow with some interesting reponses.  I like this post for three reasons. First, I am a big fan of dependency injection, it forces you to decouple your code, create cohesive interfaces, and should result in testable classes. Second, the author took the approach I usually do when trying to evaluate a technique or technology; suspend personal feelings and try to find some compelling arguments against it. Third, it proved that it is very difficult to come up with a compelling argument against dependency injection. What are the downsides to using dependency injection?

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• Using virtual functions

  - by Tucker Morgan

  I am starting to use virtual functions, and i am programming a simple text game, my question is this, if i have a virtual function called spec_abil with in a Super class called rpg_class. If you allow the player to class what class they want to play, say a mage class, a archer class, and a warrior class, which all have their own spec_abil function. How do you write it so that the program knows which one to use depending on the chosen class.

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• How to ...set up new Java environment - largely interfaces...

  - by Chris Kimpton

  Hi, Looks like I need to setup a new Java environment for some interfaces we need to build. Say our system is X and we need to interfaces to systems A, B and C. Then we will be writing interfaces X-A, X-B, X-C. Our system has a bus within it, so the publishing on our side will be to the bus and the interface processes will be taking from the bus and mapping to the destination system. Its for a vendor based system - so most of the core code we can't touch. Currently thinking we will have several processes, one per interface we need to do. The question is how to structure things. Several of the APIs we need to work with are Java based. We could go EJB, but prefer to keep it simple, one process per interface, so that we can restart them individually. Similarly SOA seems overkill, although I am probably mixing my thoughts about implementations of it compared to the concepts behind it... Currently thinking that something Spring based is the way to go. In true, "leverage a new tech if possible"-style, I am thinking maybe we can shoe horn some jruby into this, perhaps to make the APIs more readable, perhaps event-machine-like and to make the interface code more business-friendly, perhaps even storing the mapping code in the DB, as ruby snippets that get mixed in... but thats an aside... So, any comments/thoughts on the Spring approach - anything more up-to-date/relevant these days. EDIT: Looking a JRuby further, I am tempted to write it fully in JRuby... in which case do we need any frameworks at all, perhaps some gems to make things clearer... Thanks in advance, Chris

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• Is it necessary to create a database with as few tables as possible

  - by Shaheer

  Should we create a database structure with a minimum number of tables? Should it be designed in a way that everything stays in one place or is it okay to have more tables? Will it in anyway affect anything? I am asking this question because a friend of mine modified some database structure in mediaWiki. In the end, instead of 20 tables he was using only 8, and it took him 8 months to do that (it was his college assignment). EDIT I am concluding the answer as: size of the tables does NOT matter, until the case is exceptional; in which case the denormalization may help. Thanks to everyone for the answers.

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• Adding a forum to an existing site

  - by Andrew Heath

  I've got a site with ~500 registered members, 300 of which are what you'd call "active". Site data is kept in a MySQL dbase. I'd like to add a myBB forum to the site, but this question applies to any forum really. What I very much want to avoid is requiring my users to register both on the site and on the forum because my userbase is not technically literate and this would confuse a lot of them. However the forum software has its own registration, login, cookie, and password management system which naturally are different from the site's mechanics. I envision the following possibilities: install myBB into the existing database and customize the login code to unify the two systems. This would probably mean changing the site's code to use the myBB system as that would likely be less painful to refactor and wouldn't hurt future myBB upgrade ability. install myBB into separate database and write a bridging script of some sort that auto-registers existing site users with the forum if they elect to participate. Also check new forum registrations against the site's username list to prevent newcomers from taking existing names. run them fully separate and force users to re-register (easiest for ME, but least desirable for them) I would like a suggested course of action from those who have trod this path before... Thank you.

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• NCurses, scrolling of multiline items, "current item" pointer and "selected items"

  - by mjf

  I am looking for hints/ideas for the best (most effective) way on how to scroll multi-line items as well as emphasizing of the "current item" and "selected items" such as: 1 FOO ITEM 1 Foo sub-item 2 Foo sub-item 3 Foo sub-item 2 BAR ITEM 1 Bar sub-item 3 BAZ ITEM 1 Baz sub-item 2 Baz sub-item 4 RAB ITEM 5 ZZZ ITEM 1 Zzz sub-item 2 Zzz sub-item 3 Zzz sub-item 4 Zzz sub-item using NCurses (some combination of windows, sub-windows, pads, copywin? Uff! In fact, the lines could exceed the stdscr's width so that possibility to scroll left/right would be also nice - pads?)... The whole items (including the sub-items) are supposed to be emphasized as full-width window/pad areas. The "current item" (including it's set of lines) should be emphasized (i.e. using A_BOLD), selected set of items of choice (including the set of lines for each the selected item) should be emphasized in another way (i.e. using A_REVERSE). What would you choose to cope with it the most effective NCurses way? (The less redrawals/refreshes the better and terminal is supposed to have the ability to change it's size - such as XTerm running under "floating window" management.) Thank you for your ideas (or perhaps some piece of code where something similar is already solved - I was not able to find anything helpful on the Internet. I mean I am not going to copy/paste foreign code but programming NCurses properly is still somehow difficult to me). P.S.: Would you suggest to "smooth-scroll" +1/-1 screen line or rather "jump-scroll" +lines/-lines of the items? (I personally prefer the latter one.) Sincerely, -- mjf

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• Architecture for Social Graph data that has a Time Frame Associated?

  - by Jay Stevens

  I am adding some "social" type features to an existing application. There are a limited # of node & edge types. Overall the data itself is relatively small (50,000 - 70,000 for each type of node) there will be a number of edges (relationships) between them (almost all directional). This, I know, is relatively easy to represent with an SDF store (such as BrightstarDB) or something like Microsoft's Trinity (or really many of the noSQL options). The thing that, I think, makes this a unique use case is that each relationship will have a timeframe associated with it (start and end dates). Right now, I'm thinking of just storing this in a relational structure and dealing with the headaches of "traversing the graph", but I'm looking for suggestions on a better approach (both in terms of data structure and server): Column ================ From_Node_ID Relationship To_Node_ID StartDate EndDate Any suggestions or thoughts are welcomed.

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