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  • Teamwork 101 for the solo newbie

    - by clankercrusher
    Forgive my newbishness but I have a question to ask about teamwork...mainly because I stink at it. Most of my projects up until this point have been solo so I have a very limited experience with teamwork. I did make graphics for a game that was being developed by several people, but that was completely different than programming with several different people. Right now I'm working with someone else on an indie MMO along with a few other team members. I've already made some pretty stupid mistakes, (like rewriting EVERYTHING) so I have two questions for you guys: 1) What are some of the most common mistakes that people make in a team environment and how can they be avoided? 2) How can the structure of your program be altered to allow for multiple teams members to work on different parts of the program at the same time? P.S. Is this the right stack exchange site for this type of question? (if not, where does it go? Thanks)

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  • Podcast interview with Michael Kane

    - by mhornick
    In this podcast interview with Michael Kane, Data Scientist and Associate Researcher at Yale University, Michael discusses the R statistical programming language, computational challenges associated with big data, and two projects involving data analysis he conducted on the stock market "flash crash" of May 6, 2010, and the tracking of transportation routes bird flu H5N1. Michael also worked with Oracle on Oracle R Enterprise, a component of the Advanced Analytics option to Oracle Database Enterprise Edition. In the closing segment of the interview, Michael comments on the relationship between the data analyst and the database administrator and how Oracle R Enterprise provides secure data management, transparent access to data, and improved performance to facilitate this relationship. Listen now...

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  • A Quick Primer on SharePoint Customization

    - by PeterBrunone
    Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman","serif";} This one goes out to all the people who have been asked to change the way a SharePoint site looks.  Management wants to know how long it will take, and you can whip that out by tomorrow, right?  If you don't have time to prepare a treatise on what's involved, or if you just want to lend some extra weight to your case by quoting a blogger who was an MVP for seven years, then dive right in; this post is for you. There are three main components of SharePoint visual customization:   1)       Theme – A theme encompasses all the standardized text formatting and coloring (borders, fonts, etc), including the background images of various sections. All told, there could be around 50 images involved, and a few hundred CSS (style) classes.  Installing a theme once it’s been created is no great feat.  Given the number of pieces, of course, creating a new theme could take anywhere from a day to a week… once decisions have been made about the desired appearance. 2)      Master Page – A master page provides the framework for page layout.  This includes all the top and side menus, where content shows up, et cetera.  Master pages have been around for a long time in ASP.NET (Microsoft’s web development platform), and they do require some .NET programming knowledge.  Beyond that, in SharePoint, there are a few dozen controls which the system expects find on a given page.  They’re not all used at once, but if they’re not there when they’re needed, chaos ensues.  Estimating a custom master page is difficult, as it depends on the level of customization.  I’ve been on projects where I was brought in simply to fix some problems and add a few finishing touches, and it took 2-3 weeks.  Master page customization requires a large amount of testing time to make sure that the HTML, JavaScript, CSS, and control placement all work well together. 3)      Individual page layout – Each page (ideally) uses a master page for its template, but within the content areas defined by the master page, web parts can be added, removed, and configured from within the browser.  The wireframe that Brent provided could most likely be completed simply by manipulating the content on the home page in this fashion, and we had allowed about a day of effort for the task.  If needed, further functionality can be provided by an experienced ASP.NET developer; custom forms are a common example.  This of course is a bit more in-depth than simple content manipulation and could take several days per page (or more; there’s really no way to quantify this without a set of requirements).   That’s basically it.  To recap:  Fonts and coloring are done with themes, and can take anywhere from a day to a week to create (not counting creative time); required technical skills include HTML, CSS, and image manipulation.  Templated layout is done with master pages, and generally requires a developer familiar with both ASP.NET and SharePoint in particular; it can have far-reaching consequences depending on the complexity of the changes, and could add weeks or months to a project.  Page layout can be as simple as content manipulation in the web browser, taking a few hours per page, or it can involve more detail, like custom forms, and can require programming expertise and significantly more development time.

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  • How to render axometric/isometric tiles that are a 2d array in logic, but inclined 45º visually?

    - by TheLima
    I am making a tile-based strategy game which i plan to have 2.5D visuals in an axometric/isometric fashion. Right now i'm programming it's logic and rendering it as a literal 2-dimensional array (perfect squares, like an isometric top-down-view). In short, i have something like this: And i want to turn it to something like this: Do i keep going on the 2d-array logic? Is it all just a change in rendering behavior, as i'm thinking it is? or 2d-array is the wrong approach for my objective and I should change before it's too late? What are the ways of doing it, anyways? How should i apply the 2.5D axometric/isometric view (45º rotation to the side, and 45º rotation upwards)?

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  • Why are there so many spaces and line breaks in Unicode?

    - by maaartinus
    Unicode has maybe 50 spaces \u0009\u000A-\u000D\u0020\u0085\u00A0\u1680\u180E\u2000-\u200A\u2028\u2029\u202F\u205F\u3000][\u0009\u000A-\u000D\u0020\u0085\u00A0\u1680\u180E\u2000-\u200A\u2028\u2029\u202F\u205F\u3000 and 6 line breaks not only CRLF, LF, CR, but also NEL (U+0085), PS (U+2029) and LS (U+2028). Maybe I could understand most of the spaces and PS ("Paragraph separator"), but what are "Next Line" and "Line separator" good for? It all looks like invented by a very big committee where everybody wanted their own space and the leaders were granted one line break each. But seriously, how do you deal with it when your programming language doesn't support it (or does it wrong as e.g. Java does)?

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  • Wozu eigentlich Oracle Linux?

    - by Manuel Hossfeld
    Zur Abwechslung gibt es heute mal einen kürzeren Artikel, und zwar zum Thema "Oracle Linux". Der eine oder andere mag sich vielleicht schon mal gefragt haben, warum man sich mit diesem "Red Hat Klon" überhaupt auseinandersetzen sollte. Gibt es neben dem "Support aus einer Hand"-Argument noch andere Gründe, warum sich Kunden dafür entscheiden, Oracle Linux einzusetzen? Diese und ähnliche Fragen hat eine kürzlich erschienene IDC-Studie beleuchtet. Sie trägt den Titel: "Oracle Linux Takes Its Place in the Operating Systems Market". Interessant ist vor allem ein konkretes Kundenbeispiel am Ende der Studie. Da es thematisch gerade passt sei zum Schluss noch ein kleiner Hinweis in eigener Sache erlaubt:Viele der in dem Paper erwähnten Aspekte und Features (wie z.B. KSplice für Reboot-freie Kernel-Updates) werden auch auf der diesjährigen DOAG-Konferenz in Nürnberg behandelt. Mein Kollege Lenz Grimmer und ich halten dort einen Vortrag mit dem Titel: "Oracle Linux - Best Practices und Nutzen (nicht nur) für die Oracle DB"20.11.2012, 15:00 - 15:45 Uhr, Raum Kiew

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  • How I understood monads, part 1/2: sleepless and self-loathing in Seattle

    For some time now, I had been noticing some interest for monads, mostly in the form of unintelligible (to me) blog posts and comments saying oh, yeah, thats a monad about random stuff as if it were absolutely obvious and if I didnt know what they were talking about, I was probably an uneducated idiot, ignorant about the simplest and most fundamental concepts of functional programming. Fair enough, I am pretty much exactly that. Being the kind of guy who can spend eight years in college just to...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Url Navigation

    - by russ.bishop
    One of the new features is URL-based navigation which is useful for creating intranet links or auto-generating email links (such as from workflow systems, etc). For IIS 6 and earlier, the format is as follows: http://machine/drm-client/Logon.aspx? app=<appname>&action=go&ver=<version name>&hier=<hier name>&node=<node name> Just replace the fields with their appropriate values (URL-encoded of course). <node name> is optional. If provided it will open the hierarchy and expand directly to the target node. Otherwise the hierarchy is opened to the top node. Note that if the specified version is not loaded it will be loaded automatically.

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  • How to code UI / HUD in Entity System?

    - by Sylpheed
    I think I already got the idea of the Entity System inspired by Adam Martin (t-machine). I want to start using this for my next project. I already know the basic of Entity, Components, and Systems. My problem is how to handle UI / HUD. For example, a quest window, skill window, character info window, etc. How do you handle UI events (eg. pressing a button)? These are stuff that doesn't need to be processed every frame. Currently, I'm using MVC to code UI but I don't think that'll be compatible for Entity System. I've read that Entity System is embedded on a larger OOP. I don't know if UI is outside of ES or not. How do I approach this one?

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  • Is there a standard way to store 3D meshes to easily communicate between libraries?

    - by awiebe
    In a 3D game lots of different systems need to know about geometry data, however the only way they seem to be able to agree to on in representing it by an array of triangles. Can anyone recommend a good geometry manipulation library that will allow me to easily integrate the drawing library(OpenGL), the physics engine(Bullet), Serialization(Several 3D file formats) and my own code(objective-c++). Focus on the a representation between the drawing library and the physics engine. Also if the library can triangulate a mesh definition that would be very helpful. My code can work around what exists already.

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  • What is a name for a job where you do system analysis, project management and data diagramming?

    - by David Archer
    In the last 4 months I've been able to manage a team and step away from the coding for a bit. I've been planning the system in full (both System Analysis and project managing, alongside action and data diagramming) writing the technical documentation, the code's architecture, keeping track of the other guys doing the actual coding, QA, bug reports and dealing with clients. I had to take two days' training on node.js just to see if it would be suitable for a project we were considering. Is there a name for this job? Project Manager and Systems Architect don't quite seem to have the same stuff, and IT manager seems way off. I only want to know so that I can get some qualification towards it and try to move into this kind of work full-time.

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  • APress Deal of the Day 13/August/2014 - Pro ASP.NET MVC 4

    - by TATWORTH
    Originally posted on: http://geekswithblogs.net/TATWORTH/archive/2014/08/13/apress-deal-of-the-day-13august2014---pro-asp.net-mvc.aspxToday’s $10 Deal of the Day from APress at http://www.apress.com/9781430242369 is Pro ASP.NET MVC 4. Adam Freeman is an excellent author and I recommend this book to all my readers. “The ASP.NET MVC 4 Framework is the latest evolution of Microsoft’s ASP.NET web platform. It provides a high-productivity programming model that promotes cleaner code architecture, test-driven development, and powerful extensibility, combined with all the benefits of ASP.NET.”

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  • CLR via C# 3rd Edition is out

    - by Abhijeet Patel
    Time for some book news update. CLR via C#, 3rd Edition seems to have been out for a little while now. The book was released in early Feb this year, and needless to say my copy is on it’s way. I can barely wait to dig in and chew on the goodies that one of the best technical authors and software professionals I respect has in store. The 2nd edition of the book was an absolute treat and this edition promises to be no less. Here is a brief description of what’s new and updated from the 2nd edition. Part I – CLR Basics Chapter 1-The CLR’s Execution Model Added about discussion about C#’s /optimize and /debug switches and how they relate to each other. Chapter 2-Building, Packaging, Deploying, and Administering Applications and Types Improved discussion about Win32 manifest information and version resource information. Chapter 3-Shared Assemblies and Strongly Named Assemblies Added discussion of TypeForwardedToAttribute and TypeForwardedFromAttribute. Part II – Designing Types Chapter 4-Type Fundamentals No new topics. Chapter 5-Primitive, Reference, and Value Types Enhanced discussion of checked and unchecked code and added discussion of new BigInteger type. Also added discussion of C# 4.0’s dynamic primitive type. Chapter 6-Type and Member Basics No new topics. Chapter 7-Constants and Fields No new topics. Chapter 8-Methods Added discussion of extension methods and partial methods. Chapter 9-Parameters Added discussion of optional/named parameters and implicitly-typed local variables. Chapter 10-Properties Added discussion of automatically-implemented properties, properties and the Visual Studio debugger, object and collection initializers, anonymous types, the System.Tuple type and the ExpandoObject type. Chapter 11-Events Added discussion of events and thread-safety as well as showing a cool extension method to simplify the raising of an event. Chapter 12-Generics Added discussion of delegate and interface generic type argument variance. Chapter 13-Interfaces No new topics. Part III – Essential Types Chapter 14-Chars, Strings, and Working with Text No new topics. Chapter 15-Enums Added coverage of new Enum and Type methods to access enumerated type instances. Chapter 16-Arrays Added new section on initializing array elements. Chapter 17-Delegates Added discussion of using generic delegates to avoid defining new delegate types. Also added discussion of lambda expressions. Chapter 18-Attributes No new topics. Chapter 19-Nullable Value Types Added discussion on performance. Part IV – CLR Facilities Chapter 20-Exception Handling and State Management This chapter has been completely rewritten. It is now about exception handling and state management. It includes discussions of code contracts and constrained execution regions (CERs). It also includes a new section on trade-offs between writing productive code and reliable code. Chapter 21-Automatic Memory Management Added discussion of C#’s fixed state and how it works to pin objects in the heap. Rewrote the code for weak delegates so you can use them with any class that exposes an event (the class doesn’t have to support weak delegates itself). Added discussion on the new ConditionalWeakTable class, GC Collection modes, Full GC notifications, garbage collection modes and latency modes. I also include a new sample showing how your application can receive notifications whenever Generation 0 or 2 collections occur. Chapter 22-CLR Hosting and AppDomains Added discussion of side-by-side support allowing multiple CLRs to be loaded in a single process. Added section on the performance of using MarshalByRefObject-derived types. Substantially rewrote the section on cross-AppDomain communication. Added section on AppDomain Monitoring and first chance exception notifications. Updated the section on the AppDomainManager class. Chapter 23-Assembly Loading and Reflection Added section on how to deploy a single file with dependent assemblies embedded inside it. Added section comparing reflection invoke vs bind/invoke vs bind/create delegate/invoke vs C#’s dynamic type. Chapter 24-Runtime Serialization This is a whole new chapter that was not in the 2nd Edition. Part V – Threading Chapter 25-Threading Basics Whole new chapter motivating why Windows supports threads, thread overhead, CPU trends, NUMA Architectures, the relationship between CLR threads and Windows threads, the Thread class, reasons to use threads, thread scheduling and priorities, foreground thread vs background threads. Chapter 26-Performing Compute-Bound Asynchronous Operations Whole new chapter explaining the CLR’s thread pool. This chapter covers all the new .NET 4.0 constructs including cooperative cancelation, Tasks, the aralle class, parallel language integrated query, timers, how the thread pool manages its threads, cache lines and false sharing. Chapter 27-Performing I/O-Bound Asynchronous Operations Whole new chapter explaining how Windows performs synchronous and asynchronous I/O operations. Then, I go into the CLR’s Asynchronous Programming Model, my AsyncEnumerator class, the APM and exceptions, Applications and their threading models, implementing a service asynchronously, the APM and Compute-bound operations, APM considerations, I/O request priorities, converting the APM to a Task, the event-based Asynchronous Pattern, programming model soup. Chapter 28-Primitive Thread Synchronization Constructs Whole new chapter discusses class libraries and thread safety, primitive user-mode, kernel-mode constructs, and data alignment. Chapter 29-Hybrid Thread Synchronization Constructs Whole new chapter discussion various hybrid constructs such as ManualResetEventSlim, SemaphoreSlim, CountdownEvent, Barrier, ReaderWriterLock(Slim), OneManyResourceLock, Monitor, 3 ways to solve the double-check locking technique, .NET 4.0’s Lazy and LazyInitializer classes, the condition variable pattern, .NET 4.0’s concurrent collection classes, the ReaderWriterGate and SyncGate classes.

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  • Big Data – Evolution of Big Data – Day 3 of 21

    - by Pinal Dave
    In yesterday’s blog post we answered what is the Big Data. Today we will understand why and how the evolution of Big Data has happened. Though the answer is very simple, I would like to tell it in the form of a history lesson. Data in Flat File In earlier days data was stored in the flat file and there was no structure in the flat file.  If any data has to be retrieved from the flat file it was a project by itself. There was no possibility of retrieving the data efficiently and data integrity has been just a term discussed without any modeling or structure around. Database residing in the flat file had more issues than we would like to discuss in today’s world. It was more like a nightmare when there was any data processing involved in the application. Though, applications developed at that time were also not that advanced the need of the data was always there and there was always need of proper data management. Edgar F Codd and 12 Rules Edgar Frank Codd was a British computer scientist who, while working for IBM, invented the relational model for database management, the theoretical basis for relational databases. He presented 12 rules for the Relational Database and suddenly the chaotic world of the database seems to see discipline in the rules. Relational Database was a promising land for all the unstructured database users. Relational Database brought into the relationship between data as well improved the performance of the data retrieval. Database world had immediately seen a major transformation and every single vendors and database users suddenly started to adopt the relational database models. Relational Database Management Systems Since Edgar F Codd proposed 12 rules for the RBDMS there were many different vendors who started them to build applications and tools to support the relationship between database. This was indeed a learning curve for many of the developer who had never worked before with the modeling of the database. However, as time passed by pretty much everybody accepted the relationship of the database and started to evolve product which performs its best with the boundaries of the RDBMS concepts. This was the best era for the databases and it gave the world extreme experts as well as some of the best products. The Entity Relationship model was also evolved at the same time. In software engineering, an Entity–relationship model (ER model) is a data model for describing a database in an abstract way. Enormous Data Growth Well, everything was going fine with the RDBMS in the database world. As there were no major challenges the adoption of the RDBMS applications and tools was pretty much universal. There was a race at times to make the developer’s life much easier with the RDBMS management tools. Due to the extreme popularity and easy to use system pretty much every data was stored in the RDBMS system. New age applications were built and social media took the world by the storm. Every organizations was feeling pressure to provide the best experience for their users based the data they had with them. While this was all going on at the same time data was growing pretty much every organization and application. Data Warehousing The enormous data growth now presented a big challenge for the organizations who wanted to build intelligent systems based on the data and provide near real time superior user experience to their customers. Various organizations immediately start building data warehousing solutions where the data was stored and processed. The trend of the business intelligence becomes the need of everyday. Data was received from the transaction system and overnight was processed to build intelligent reports from it. Though this is a great solution it has its own set of challenges. The relational database model and data warehousing concepts are all built with keeping traditional relational database modeling in the mind and it still has many challenges when unstructured data was present. Interesting Challenge Every organization had expertise to manage structured data but the world had already changed to unstructured data. There was intelligence in the videos, photos, SMS, text, social media messages and various other data sources. All of these needed to now bring to a single platform and build a uniform system which does what businesses need. The way we do business has also been changed. There was a time when user only got the features what technology supported, however, now users ask for the feature and technology is built to support the same. The need of the real time intelligence from the fast paced data flow is now becoming a necessity. Large amount (Volume) of difference (Variety) of high speed data (Velocity) is the properties of the data. The traditional database system has limits to resolve the challenges this new kind of the data presents. Hence the need of the Big Data Science. We need innovation in how we handle and manage data. We need creative ways to capture data and present to users. Big Data is Reality! Tomorrow In tomorrow’s blog post we will try to answer discuss Basics of Big Data Architecture. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Big Data, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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  • A Simple Online Document Management System Using Asp.net MVC 3

    - by RazanPaul
    Nowadays we have a number of online file management systems (e.g. DropBox, SkyDrive and Google Drive). People can use them to manage different types of documents. However, one might need a system to manage documents when they do not want to publish the company documents to the cloud. In that case, they need to build an online document management system. This project is intended to meet this purpose. However, it is in the early stage. All the functionalities seem working. A lot of work is needed in the UI. Besides this, code needs refactoring. Please find the project at the following link: https://documentmanagementsystem.codeplex.com/

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  • Prevent service from starting

    - by Evan Plaice
    So, I do Arduino development on my system to program arduinos using the FTDI USB programming interface (if you have no idea what this means don't worry). The issue arises because the FTDI interface uses tty to communicate and it conflicts with one of the default ubuntu services. The default service in question is called brltty (which enables braille accessibility for people with impaired vision). Considering that I don't have any particular use for this service and it's annoying to stop it manually (using 'service brltty stop') after I restart my system... Where would I configure this (or any) service to prevent it from loading on startup? Note: I also have this issue with qemu-kvm conflicting with virtualbox.

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  • Computer Science or Computer Engineering for Data Science and Machine Learning

    - by ATMathew
    I'm a 25 year old data consultant who is considering returning to school to get a second bachelors degree in computer science or engineering. My interest is data science and machine learning. I use programming as a means to an end, and use languages like Python, R, C, Java, and Hadoop to find meaning in large data sets. Would a computer science or computer engineering degree be better for this? I realize that a statistics degree may be even more beneficial, but I'll be at a school which dosn't have a stats department or a computational math department.

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  • how should I network my turn based game?

    - by ddriver1
    I'm writing a very basic turn based strategy game which allows a player to select units and attack enemy units on their turn. The game is written in Java using the slick2d library and I plan to use kyronet for the networking api. I want the game to be networked, but I do not know how I should go about it. My current idea is to connect two users together, and the first one to join the game becomes the game host, while the other becomes the client. However after reading http://gafferongames.com/networking-for-game-programmers/what-every-programmer-needs-to-know-about-game-networking/ it seems my game would be suited to a peer to peer lockstep model. Would that make programming the networking side much easier? Any suggestions on how I should structure my networking would be greatly appreciated

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  • Liskov Substitution Principle and the Oft Forgot Third Wheel

    - by Stacy Vicknair
    Liskov Substitution Principle (LSP) is a principle of object oriented programming that many might be familiar with from the SOLID principles mnemonic from Uncle Bob Martin. The principle highlights the relationship between a type and its subtypes, and, according to Wikipedia, is defined by Barbara Liskov and Jeanette Wing as the following principle:   Let be a property provable about objects of type . Then should be provable for objects of type where is a subtype of .   Rectangles gonna rectangulate The iconic example of this principle is illustrated with the relationship between a rectangle and a square. Let’s say we have a class named Rectangle that had a property to set width and a property to set its height. 1: Public Class Rectangle 2: Overridable Property Width As Integer 3: Overridable Property Height As Integer 4: End Class   We all at some point here that inheritance mocks an “IS A” relationship, and by gosh we all know square IS A rectangle. So let’s make a square class that inherits from rectangle. However, squares do maintain the same length on every side, so let’s override and add that behavior. 1: Public Class Square 2: Inherits Rectangle 3:  4: Private _sideLength As Integer 5:  6: Public Overrides Property Width As Integer 7: Get 8: Return _sideLength 9: End Get 10: Set(value As Integer) 11: _sideLength = value 12: End Set 13: End Property 14:  15: Public Overrides Property Height As Integer 16: Get 17: Return _sideLength 18: End Get 19: Set(value As Integer) 20: _sideLength = value 21: End Set 22: End Property 23: End Class   Now, say we had the following test: 1: Public Sub SetHeight_DoesNotAffectWidth(rectangle As Rectangle) 2: 'arrange 3: Dim expectedWidth = 4 4: rectangle.Width = 4 5:  6: 'act 7: rectangle.Height = 7 8:  9: 'assert 10: Assert.AreEqual(expectedWidth, rectangle.Width) 11: End Sub   If we pass in a rectangle, this test passes just fine. What if we pass in a square?   This is where we see the violation of Liskov’s Principle! A square might "IS A” to a rectangle, but we have differing expectations on how a rectangle should function than how a square should! Great expectations Here’s where we pat ourselves on the back and take a victory lap around the office and tell everyone about how we understand LSP like a boss. And all is good… until we start trying to apply it to our work. If I can’t even change functionality on a simple setter without breaking the expectations on a parent class, what can I do with subtyping? Did Liskov just tell me to never touch subtyping again? The short answer: NO, SHE DIDN’T. When I first learned LSP, and from those I’ve talked with as well, I overlooked a very important but not appropriately stressed quality of the principle: our expectations. Our inclination is to want a logical catch-all, where we can easily apply this principle and wipe our hands, drop the mic and exit stage left. That’s not the case because in every different programming scenario, our expectations of the parent class or type will be different. We have to set reasonable expectations on the behaviors that we expect out of the parent, then make sure that those expectations are met by the child. Any expectations not explicitly expected of the parent aren’t expected of the child either, and don’t register as a violation of LSP that prevents implementation. You can see the flexibility mentioned in the Wikipedia article itself: A typical example that violates LSP is a Square class that derives from a Rectangle class, assuming getter and setter methods exist for both width and height. The Square class always assumes that the width is equal with the height. If a Square object is used in a context where a Rectangle is expected, unexpected behavior may occur because the dimensions of a Square cannot (or rather should not) be modified independently. This problem cannot be easily fixed: if we can modify the setter methods in the Square class so that they preserve the Square invariant (i.e., keep the dimensions equal), then these methods will weaken (violate) the postconditions for the Rectangle setters, which state that dimensions can be modified independently. Violations of LSP, like this one, may or may not be a problem in practice, depending on the postconditions or invariants that are actually expected by the code that uses classes violating LSP. Mutability is a key issue here. If Square and Rectangle had only getter methods (i.e., they were immutable objects), then no violation of LSP could occur. What this means is that the above situation with a rectangle and a square can be acceptable if we do not have the expectation for width to leave height unaffected, or vice-versa, in our application. Conclusion – the oft forgot third wheel Liskov Substitution Principle is meant to act as a guidance and warn us against unexpected behaviors. Objects can be stateful and as a result we can end up with unexpected situations if we don’t code carefully. Specifically when subclassing, make sure that the subclass meets the expectations held to its parent. Don’t let LSP think you cannot deviate from the behaviors of the parent, but understand that LSP is meant to highlight the importance of not only the parent and the child class, but also of the expectations WE set for the parent class and the necessity of meeting those expectations in order to help prevent sticky situations.   Code examples, in both VB and C# Technorati Tags: LSV,Liskov Substitution Principle,Uncle Bob,Robert Martin,Barbara Liskov,Liskov

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  • Join us for Live Oracle Linux and Oracle VM Cloud Events in Europe

    - by Monica Kumar
    Join us for a series of live events and discover how Oracle VM and Oracle Linux offer an integrated and optimized infrastructure for quickly deploying a private cloud environment at lower cost. As one of the most widely deployed operating systems today, Oracle Linux delivers higher performance, better reliability, and stability, at a lower cost for your cloud environments. Oracle VM is an application-driven server virtualization solution fully integrated and certified with Oracle applications to deliver rapid application deployment and simplified management. With Oracle VM, you have peace of mind that the entire Oracle stack deployed is fully certified by Oracle. Register now for any of the upcoming events, and meet with Oracle experts to discuss how we can help in enabling your private cloud. Nov 20: Foundation for the Cloud: Oracle Linux and Oracle VM (Belgium) Nov 21: Oracle Linux & Oracle VM Enabling Private Cloud (Germany) Nov 28: Realize Substantial Savings and Increased Efficiency with Oracle Linux and Oracle VM (Luxembourg) Nov 29: Foundation for the Cloud: Oracle Linux and Oracle VM (Netherlands) Dec 5: MySQL Tech Tour, including Oracle Linux and Oracle VM (France) Hope to see you at one of these events!

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  • HTG Explains: Why It’s Good That Your Computer’s RAM Is Full

    - by Chris Hoffman
    Is Windows, Linux, Android, or another operating system using a lot of RAM? Don’t panic! Modern operating systems use RAM as a file cache to speed things up. Assuming your computer is performing well, there’s nothing to worry about. While it may seem counterintuitive to those of us who remember our computers always being starved for RAM, high RAM usage means your RAM is being put to good use. Empty RAM is wasted RAM. HTG Explains: Why It’s Good That Your Computer’s RAM Is Full 10 Awesome Improvements For Desktop Users in Windows 8 How To Play DVDs on Windows 8

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  • Is it okay to be generalist?

    - by Londoner
    I work at a ~50 employee company (UK), where all the technical people do a bit of everything. Specialising in anything for very long (6 months) is discouraged. For example, last week, I built a new Debian webserver, refactored some Perl, sat on a sales phone call, did a tape backup, reviewed code, built and deployed an RPM, gave opinions about x, y, z... With such a work scheme, I have gained a general knowledge how many things work, and pretty specific knowledge. I maybe program for 5 hours a week, despite officially being a developer. Does anyone else work like this, (or is this company unique)? Is it a problem to have skills developed in this way? (i.e. know a bit about everything in a certain domain, rather than know everything about say, one programming language?) Is it okay to be a generalist?

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  • New Year's Resolution: Highest Availability at the Lowest Cost

    - by margaret.hamburger(at)oracle.com
    Don't miss this Webcast: Achieve 24/7 Cloud Availability Without Expensive Redundancy Event Date: 01/11/2011 10:00 AM Pacific Standard Time You'll learn how Oracle's Maximum Availability Architecture and Oracle Database 11g help you: Achieve the highest availability at the lowest cost Protect your systems from unplanned downtime Eliminate idle redundancy Register Now! var gaJsHost = (("https:" == document.location.protocol) ? "https://ssl." : "http://www."); document.write(unescape("%3Cscript src='" + gaJsHost + "google-analytics.com/ga.js' type='text/javascript'%3E%3C/script%3E")); try { var pageTracker = _gat._getTracker("UA-13185312-1"); pageTracker._trackPageview(); } catch(err) {}

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  • WebForms vs MVC (again)

    There's a new video up on www.asp.net which aims to help developers pick between ASP.NET WebForms and ASP.NET MVC. The video boils down to 5 benefits per technology which Microsoft thinks you should consider. Let's go over the points, shall we? First, ASP.NET WebForms: 1 - Familiar control and event base programming model The claim here is that the ASP.NET model is comfortable for WinForm programmers (thankfully this unbiased analysis left out who it's more familiar for). This is largely...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • How to Quickly Encrypt Removable Storage Devices with Ubuntu

    - by Chris Hoffman
    Ubuntu can quickly encrypt USB flash drives and external hard drives. You’ll be prompted for your passphrase each time you connect the drive to your computer – your private data will be secure, even if you misplace the drive. Ubuntu’s Disk Utility uses LUKS (Linux Unified Key Setup) encryption, which may not be compatible with other operating systems. However, the drive will be plug-and-play with any Linux system running the GNOME desktop. HTG Explains: What Is RSS and How Can I Benefit From Using It? HTG Explains: Why You Only Have to Wipe a Disk Once to Erase It HTG Explains: Learn How Websites Are Tracking You Online

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