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• Who should write the test plan?

  - by Cheng Kiang

  Hi, I am in the in-house development team of my company, and we develop our company's web sites according to the requirements of the marketing team. Before releasing the site to them for acceptance testing, we were requested to give them a test plan to follow. However, the development team feels that since the requirements came from the requestors, they would have the best knowledge of what to test, what to lookout for, how things should behave etc and a test plan is thus not required. We are always in an argument over this, and developers find it a waste of time to write down things like:- Click on button A. Key in XYZ in the form field and click button B. You should see behaviour C. which we have to repeat for each requirement/feature requested. This is basically rephrasing what's already in the requirements document. We are moving towards using an Agile approach for managing our projects and this is also requested at the end of each iteration. Unit and integration testing aside, who should be the one to come up with the end user acceptance test plan? Should it be the reqestors or the developers? Many thanks in advance. Regards CK

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• How to structure my GUI agnostic project?

  - by Nezreli

  I have a project which loads from database a XML file which defines a form for some user. XML is transformed into a collection of objects whose classes derive from single parent. Something like Control - EditControl - TextBox Control - ContainterControl - Panel Those classes are responsible for creation of GUI controls for three different enviroments: WinForms, DevExpress XtraReports and WebForms. All three frameworks share mostly the same control tree and have a common single parent (Windows.Forms.Control, XrControl and WebControl). So, how to do it? Solution a) Control class has abstract methods Control CreateWinControl(); XrControl CreateXtraControl(); WebControl CreateWebControl(); This could work but the project has to reference all three frameworks and the classes are going to be fat with methods which would support all three implementations. Solution b) Each framework implementation is done in separate projects and have the exact class tree like the Core project. All three implementations are connected using a interface to the Core class. This seems clean but I'm having a hard time wrapping my head around it. Does anyone have a simpler solution or a suggestion how should I approach this task?

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• How do you encode Algebraic Data Types in a C#- or Java-like language?

  - by Jörg W Mittag

  There are some problems which are easily solved by Algebraic Data Types, for example a List type can be very succinctly expressed as: data ConsList a = Empty | ConsCell a (ConsList a) consmap f Empty = Empty consmap f (ConsCell a b) = ConsCell (f a) (consmap f b) l = ConsCell 1 (ConsCell 2 (ConsCell 3 Empty)) consmap (+1) l This particular example is in Haskell, but it would be similar in other languages with native support for Algebraic Data Types. It turns out that there is an obvious mapping to OO-style subtyping: the datatype becomes an abstract base class and every data constructor becomes a concrete subclass. Here's an example in Scala: sealed abstract class ConsList[+T] { def map[U](f: T => U): ConsList[U] } object Empty extends ConsList[Nothing] { override def map[U](f: Nothing => U) = this } final class ConsCell[T](first: T, rest: ConsList[T]) extends ConsList[T] { override def map[U](f: T => U) = new ConsCell(f(first), rest.map(f)) } val l = (new ConsCell(1, new ConsCell(2, new ConsCell(3, Empty))) l.map(1+) The only thing needed beyond naive subclassing is a way to seal classes, i.e. a way to make it impossible to add subclasses to a hierarchy. How would you approach this problem in a language like C# or Java? The two stumbling blocks I found when trying to use Algebraic Data Types in C# were: I couldn't figure out what the bottom type is called in C# (i.e. I couldn't figure out what to put into class Empty : ConsList< ??? >) I couldn't figure out a way to seal ConsList so that no subclasses can be added to the hierarchy What would be the most idiomatic way to implement Algebraic Data Types in C# and/or Java? Or, if it isn't possible, what would be the idiomatic replacement?

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• Be liberal in what you accept... or not?

  - by Matthieu M.

  [Disclaimer: this question is subjective, but I would prefer getting answers backed by facts and/or reflexions] I think everyone knows about the Robustness Principle, usually summed up by Postel's Law: Be conservative in what you send; be liberal in what you accept. I would agree that for the design of a widespread communication protocol this may make sense (with the goal of allowing easy extension), however I have always thought that its application to HTML / CSS was a total failure, each browser implementing its own silent tweak detection / behavior, making it near impossible to obtain a consistent rendering across multiple browsers. I do notice though that there the RFC of the TCP protocol deems "Silent Failure" acceptable unless otherwise specified... which is an interesting behavior, to say the least. There are other examples of the application of this principle throughout the software trade that regularly pop up because they have bitten developpers, from the top off my head: Javascript semi-colon insertion C (silent) builtin conversions (which would not be so bad if it did not truncated...) and there are tools to help implement "smart" behavior: name matching phonetic algorithms (Double Metaphone) string distances algorithms (Levenshtein distance) However I find that this approach, while it may be helpful when dealing with non-technical users or to help users in the process of error recovery, has some drawbacks when applied to the design of library/classes interface: it is somewhat subjective whether the algorithm guesses "right", and thus it may go against the Principle of Least Astonishment it makes the implementation more difficult, thus more chances to introduce bugs (violation of YAGNI ?) it makes the behavior more susceptible to change, as any modification of the "guess" routine may break old programs, nearly excluding refactoring possibilities... from the start! And this is what led me to the following question: When designing an interface (library, class, message), do you lean toward the robustness principle or not ? I myself tend to be quite strict, using extensive input validation on my interfaces, and I was wondering if I was perhaps too strict.

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• Doing a passable 4X game AI

  - by Extrakun

  I am coding a rather "simple" 4X game (if a 4X game can be simple). It's indie in scope, and I am wondering if there's anyway to come up with a passable AI without having me spending months coding on it. The game has three major decision making portions; spending of production points, spending of movement points and spending of tech points (basically there are 3 different 'currency', currency unspent at end of turn is not saved) Spend Production Points Upgrade a planet (increase its tech and production) Build ships (3 types) Move ships from planets to planets (costing Movement Points) Move to attack Move to fortify Research Tech (can partially research a tech i.e, as in Master of Orion) The plan for me right now is a brute force approach. There are basically 4 broad options for the player - Upgrade planet(s) to its his production and tech output Conquer as many planets as possible Secure as many planets as possible Get to a certain tech as soon as possible For each decision, I will iterate through the possible options and come up with a score; and then the AI will choose the decision with the highest score. Right now I have no idea how to 'mix decisions'. That is, for example, the AI wishes to upgrade and conquer planets at the same time. I suppose I can have another logic which do a brute force optimization on a combination of those 4 decisions.... At least, that's my plan if I can't think of anything better. Is there any faster way to make a passable AI? I don't need a very good one, to rival Deep Blue or such, just something that has the illusion of intelligence. This is my first time doing an AI on this scale, so I dare not try something too grand too. So far I have experiences with FSM, DFS, BFS and A*

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• Reverse WiFi to Broadcast connection coming from a USB device

  - by Daniel Clem

  I am using the app called Clockworkmod Tether. It connects using a script ( command line " gksu ./run.sh " ) on the computer. All my programs connect to the internet perfectly, minitube, midori, transmission torrents. But the network manager does not show any connection, wired or wireless. So this may cause issues? What I want to do is take this connection, and be able to share it some way, any way, by wireless. This Acer Timeline "Aspire 5810TZ" does have an Ethernet, so wired out to a router might be an option. But I would prefer to simply reverse the Wireless card to broadcast out to about 2 or 3 devices. Is this possible? Yes I have taken a look at the other questions already posted here, but the answers are 1 year old or older, and not clear at all. I am moderately comfortable (4.5 out of 10 ) on the command line. But pretty much need line by line directions for what commands are needed and what order, ect. Edit I have already tried the method of "Left click network manager, Create New Wireless Network" It is created fine, and I am able to connect to it with a tablet, but am un-able to get an outside connection with it. Using the "Shared to other computers" option because DHCP doesn't seem to work, and WEP Passphrase Security. I get an IP address on the connected device. But as I said, won't bring up any outside webpages or the like. So perhaps this is the wrong approach?

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• Is it OK to reoccupy my old GitHub username to protect repository redirections?

  - by Idan Arye

  I'm considering changing my GitHub username from the old alias I was using as a kid to my real name. I'm concerned about my repository URLs. GitHub will redirect the old URLs, but if someone creates a new account using my old username and creates a repository with the same name as one of my repositories, the URL redirection will break and the URL will lead to their repository, not mine. Now, this is understandable, and GitHub recommends to not count on the redirect in the long term, and update all the remotes, but I'm concerned about some Vim plugins I'm hosting on GitHub. It's a common practice to manage Vim plugins with Git(either as separate repositories or as submodules), and if one of the plugins' remotes break you'll get error messages when you try to batch-update all your plugins(it happened to me once...). It's not that hard to solve, and the chances that'll happen are slim, but I would still like to avoid causing trouble to the users of my plugins... To prevent this, I think to create a new account with my old username. That way I can avoid the risk of someone else taking my old username and breaking the redirects of my old repositories. While researching this approach I've found GitHub's Name Squatting Policy. According to that policy, GitHub can delete or rename inactive accounts. To my understanding, they do this to prevent Cybersquatting, but surely this isn't the case with my fake account - I'm not holding someone else's name in an attempt to sell it to them, I'm merely occupying a name I was using to protect my old URLs... So, is it acceptable to go with this plan an create a fake account with my old username?

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• Find points whose pairwise distances approximate a given distance matrix

  - by Stephan Kolassa

  Problem. I have a symmetric distance matrix with entries between zero and one, like this one: D = ( 0.0 0.4 0.0 0.5 ) ( 0.4 0.0 0.2 1.0 ) ( 0.0 0.2 0.0 0.7 ) ( 0.5 1.0 0.7 0.0 ) I would like to find points in the plane that have (approximately) the pairwise distances given in D. I understand that this will usually not be possible with strictly correct distances, so I would be happy with a "good" approximation. My matrices are smallish, no more than 10x10, so performance is not an issue. Question. Does anyone know of an algorithm to do this? Background. I have sets of probability densities between which I calculate Hellinger distances, which I would like to visualize as above. Each set contains no more than 10 densities (see above), but I have a couple of hundred sets. What I did so far. I did consider posting at math.SE, but looking at what gets tagged as "geometry" there, it seems like this kind of computational geometry question would be more on-topic here. If the community thinks this should be migrated, please go ahead. This looks like a straightforward problem in computational geometry, and I would assume that anyone involved in clustering might be interested in such a visualization, but I haven't been able to google anything. One simple approach would be to randomly plonk down points and perturb them until the distance matrix is close to D, e.g., using Simulated Annealing, or run a Genetic Algorithm. I have to admit that I haven't tried that yet, hoping for a smarter way. One specific operationalization of a "good" approximation in the sense above is Problem 4 in the Open Problems section here, with k=2. Now, while finding an algorithm that is guaranteed to find the minimum l1-distance between D and the resulting distance matrix may be an open question, it still seems possible that there at least is some approximation to this optimal solution. If I don't get an answer here, I'll mail the gentleman who posed that problem and ask whether he knows of any approximation algorithm (and post any answer I get to that here).

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• Announcing Oracle Database Mobile Server 11gR2

  - by Eric Jensen

  I'm pleased to announce that Oracle Database Mobile Server 11gR2 has been released. It's available now for download by existing customers, or anyone who wants to try it out. New features include: Support for J2ME platforms, specifically CDC platforms including OJEC(this is in addition to our existing support for Java SE and SE Embedded) Per-application integration with Berkeley DB on Android Server-side support for Apache TomEE platform Adding support for Oracle Java Micro Edition Embedded Client (OJEC for short) is an important milestone for us; it enables Database Mobile Server to work with any of the incredibly wide array of devices that run J2ME. In particular, it enables management of  networks of embedded devices, AKA machine to machine (M2M) networks. As these types of networks become more common in areas like healthcare, automotive, and manufacturing, we're seeing demand for Database Mobile Server from new and different areas. This is in addition to our existing array of mobile device use cases. The Android integration feature with Berkeley DB represents the completion of phase I of our Android support plan, we now offer a full set of sync, device and app management features for that platform. Going forward, we plan to continue the dual-focus approach, supporting mobile platforms such as Android, and iOS (hint) on the one hand, and networks of embedded M2M devices on the other. In either case, Database Mobile Server continues to be the best way to connect data-driven applications to an Oracle backend.

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• OUM is Flexible and Scalable

  - by user535886

  Flexible and Scalable Traditionally, projects have been focused on satisfying the contents of a requirements document or rigorously conforming to an existing set of work products. Often, especially where iterative and incremental techniques have not been employed, these requirements may be inaccurate, the previous deliverables may be flawed, or the business needs may have changed since the start of the project. Fitness for business purpose, derived from the Dynamic Systems Development Method (DSDM) framework, refers to the focus of delivering necessary functionality within a required timebox. The solution can be more rigorously engineered later, if such an approach is acceptable. Our collective experience shows that applying fit-for-purpose criteria, rather than tight adherence to requirements specifications, results in an information system that more closely meets the needs of the business. In OUM, this principle is extended to refer to the execution of the method processes themselves. Project managers and practitioners are encouraged to scale OUM to be fit-for-purpose for a given situation. It is rarely appropriate to execute every activity within OUM. OUM provides guidance for determining the core set of activities to be executed, the level of detail targeted in those activities and their associated tasks, and the frequency and type of end user deliverables. The project workplan should be developed from this core. The plan should then be scaled up, rather than tailored down, to the level of discipline appropriate to the identified risks and requirements. Even at the task level, models and work products should be completed only to the level of detail required for them to be fit-for-purpose within the current iteration or, at the project level, to suit the business needs of the enterprise and to meet the contractual obligations that govern the project. OUM provides well defined templates for many of its tasks. Use of these templates is optional as determined by the context of the project. Work products can easily be a model in a repository, a prototype, a checklist, a set of application code, or, in situations where a high degree of agility is warranted, simply the tacit knowledge contained in the brain of an analyst or practitioner. For further reading on agility, see Balancing Agility and Discipline: A guide fro the Perplexed.

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• Introduction to Oracle ADF

  - by Arda Eralp

  The Oracle Application Development Framework (Oracle ADF) is an end-to-end application framework that builds on Java Platform, Enterprise Edition (Java EE) standards and open-source technologies. You can use Oracle ADF to implement enterprise solutions that search, display, create, modify, and validate data using web, wireless, desktop, or web services interfaces. Because of its declarative nature, Oracle ADF simplifies and accelerates development by allowing users to focus on the logic of application creation rather than coding details. Used in tandem, Oracle JDeveloper 11g and Oracle ADF give you an environment that covers the full development lifecycle from design to deployment, with drag-and-drop data binding, visual UI design, and team development features built in. In line with community best practices, applications you build using the Fusion web technology stack achieve a clean separation of business logic, page navigation, and user interface by adhering to a model-view-controller architecture. MVC architecture: The model layer represents the data values related to the current page The view layer contains the UI pages used to view or modify that data The controller layer processes user input and determines page navigation The business service layer handles data access and encapsulates business logic Each ADF module fits in the Fusion web application architecture. The core module in the framework is ADF Model, a data binding facility. The ADF Model layer enables a unified approach to bind any user interface to any business service, without the need to write code. The other modules that make up a Fusion web application technology stack are: ADF Business Components, which simplifies building business services. ADF Faces rich client, which offers a rich library of AJAX-enabled UI components for web applications built with JavaServer Faces (JSF). ADF Controller, which integrates JSF with ADF Model. The ADF Controller extends the standard JSF controller by providing additional functionality, such as reusable task flows that pass control not only between JSF pages, but also between other activities, for instance method calls or other task flows.

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• Inheritance vs containment while extending a large legacy project

  - by Flot2011

  I have got a legacy Java project with a lot of code. The code uses MVC pattern and is well structured and well written. It also has a lot of unit tests and it is still actively maintained (bug fixing, minor features adding). Therefore I want to preserve the original structure and code style as much as possible. The new feature I am going to add is a conceptual one, so I have to make my changes all over the code. In order to minimize changes I decided not to extend existing classes but to use containment: class ExistingClass { // .... existing code // my code adding new functionality private ExistingClassExtension extension = new ExistingClassExtension(); public ExistingClassExtension getExtension() {return extension;} } ... // somewhere in code ExistingClass instance = new ExistingClass(); ... // when I need a new functionality instance.getExtension().newMethod1(); All functionality that I am adding is inside a new ExistingClassExtension class. Actually I am adding only these 2 lines to each class that needs to be extended. By doing so I also do not need to instantiate new, extended classes all over the code and I may use existing tests to make sure there is no regression. However my colleagues argue that in this situation doing so isn't a proper OOP approach, and I need to inherit from ExistingClass in order to add a new functionality. What do you think? I am aware of numerous inheritance/containment questions here, but I think my question is different.

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• Use MvcContrib Grid to Display a Grid of Data in ASP.NET MVC

  The past six articles in this series have looked at how to display a grid of data in an ASP.NET MVC application and how to implement features like sorting, paging, and filtering. In each of these past six tutorials we were responsible for generating the rendered markup for the grid. Our Views included the <table> tags, the <th> elements for the header row, and a foreach loop that emitted a series of <td> elements for each row to display in the grid. While this approach certainly works, it does lead to a bit of repetition and inflates the size of our Views. The ASP.NET MVC framework includes an HtmlHelper class that adds support for rendering HTML elements in a View. An instance of this class is available through the Html object, and is often used in a View to create action links (Html.ActionLink), textboxes (Html.TextBoxFor), and other HTML content. Such content could certainly be created by writing the markup by hand in the View; however, the HtmlHelper makes things easier by offering methods that emit common markup patterns. You can even create your own custom HTML Helpers by adding extension methods to the HtmlHelper class. MvcContrib is a popular, open source project that adds various functionality to the ASP.NET MVC framework. This includes a very versatile Grid HTML Helper that provides a strongly-typed way to construct a grid in your Views. Using MvcContrib's Grid HTML Helper you can ditch the <table>, <tr>, and <td> markup, and instead use syntax like Html.Grid(...). This article looks at using the MvcContrib Grid to display a grid of data in an ASP.NET MVC application. A future installment will show how to configure the MvcContrib Grid to support both sorting and paging. Read on to learn more! Read More >

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• Strange and erratic transformations when using OpenGL VBOs to render scene

  - by janoside

  I have an existing iOS game with fairly simple scenes (all textured quads) and I'm using Apple's "Texture2D" class. I'm trying to convert this class to use VBOs since the vertices of my objects basically never change so I may as well not re-create them for every object every frame. I have the scene rendering using VBOs but the sizes and orientations of all rendered objects are strange and erratic - though locations seem generally correct. I've been toying with this code for a few days now, and I've found something odd: if I re-create all of my VBOs each frame, everything looks correct, even though I'm almost certain my vertices are not changing. Other notes I'm basing my work on this tutorial, and therefore am also using "IBOs" I create my buffers before rendering begins My buffers include vertex and texture data I'm using OpenGL ES 1.1 Fearing some strange effect of the current matrix GL state at the time of buffer creation I've also tried wrapping my buffer-setup code in a "pushMatrix-loadIdentity-popMatrix" block which (as expected) had no effect I'm aware that various articles have been published demonstrating that VBOs may not help performance, but I want to understand this problem and at least have the option to use them. I realize this is a shot in the dark, but has anyone else experienced this type of strange behavior? What might I be doing to result in this behavior? It's rather difficult for me to isolate the problem since I'm working in an existing, moderately complex project, so suggestions about how to approach the problem are also quite welcome.

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• Domain changes required for SSL integration

  - by user131003

  Currently my site supports regular payment options (User is taken to Payment Gateway/PG website). Now I'm trying to implement "seamless" PG integration. I need SSL for this. I'm having a dedicated server with 5 static IPs from Hostgator/HG. options: I take SSL for www.my_domain.com. According to HG, I need to change IP of main site as current IP is not really dedicated as it is being shared by cpanel etc. So They need to bind another dedicated IP to main domain for SSL to work. This would required DNS change for main website and hence cause few hours downtime (which is ok). I've noticed that most of the e-commerce websites are using subdomains like secure.my_domain.com for ssl/https. This sounds like a better approach. But I've got few doubts in this case: a) Would I need to re-register with existing PGs (Paypal, Google Checkout, Authorize.net) if I switch to subdomain? Re-registering is not an option for me. b) Would DNS change be required for www.my_domain.com in this case. This confusion arose because of following reply from HG : "If the sub domain secure.my_domain.com is added to an existing cPanel it will use the IP for that cPanel so as long as it is a Dedicated IP that will be fine. If secure.my_domain.com gets setup as its own cPanel it will need to be assigned to a Dedicated IP which would have a DNS change involved.". Please suggest?

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• How can I get started using TDD to code some simple functionality?

  - by Gabriel

  I basically have the gist of TDD. I'm sold that it's useful and I've got a reasonable command of the MSTEST framework. However, to date I have not been able to graduate to using it as a primary development method. Mostly, I use it as a surrogate for writing console apps as test drivers (my traditional approach). The most useful thing about it for me is the way it absorbs the role of regression testing. I have not yet built anything yet that specifically isolates various testable behaviors, which is another big part of the picture I know. So this question is to ask for pointers on what the first test(s) I might write for the following development task: I want to produce code that encapsulates task execution in the fashion of producer/consumer. I stopped and decided to write this question after I wrote this code (wondering if I could actually use TDD for real this time) Code: interface ITask { Guid TaskId { get; } bool IsComplete { get; } bool IsFailed { get; } bool IsRunning { get; } } interface ITaskContainer { Guid AddTask(ICommand action); } interface ICommand { string CommandName { get; } Dictionary<string, object> Parameters { get; } void Execute(); }

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• How to avoid throwing vexing exceptions?

  - by Mike

  Reading Eric Lippert's article on exceptions was definitely an eye opener on how I should approach exceptions, both as the producer and as the consumer. However, I'm still struggling to define a guideline regarding how to avoid throwing vexing exceptions. Specifically: Suppose you have a Save method that can fail because a) Somebody else modified the record before you, or b) The value you're trying to create already exists. These conditions are to be expected and not exceptional, so instead of throwing an exception you decide to create a Try version of your method, TrySave, which returns a boolean indicating if the save succeeded. But if it fails, how will the consumer know what was the problem? Or would it be best to return an enum indicating the result, kind of Ok/RecordAlreadyModified/ValueAlreadyExists? With integer.TryParse this problem doesn't exist, since there's only one reason the method can fail. Is the previous example really a vexing situation? Or would throwing an exception in this case be the preferred way? I know that's how it's done in most libraries and frameworks, including the Entity framework. How do you decide when to create a Try version of your method vs. providing some way to test beforehand if the method will work or not? I'm currently following these guidelines: If there is the chance of a race condition, then create a Try version. This prevents the need for the consumer to catch an exogenous exception. For example, in the Save method described before. If the method to test the condition pretty much would do all that the original method does, then create a Try version. For example, integer.TryParse(). In any other case, create a method to test the condition.

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• vector rotations for branches of a 3d tree

  - by freefallr

  I'm attempting to create a 3d tree procedurally. I'm hoping that someone can check my vector rotation maths, as I'm a bit confused. I'm using an l-system (a recursive algorithm for generating branches). The trunk of the tree is the root node. It's orientation is aligned to the y axis. In the next iteration of the tree (e.g. the first branches), I might create a branch that is oriented say by +10 degrees in the X axis and a similar amount in the Z axis, relative to the trunk. I know that I should keep a rotation matrix at each branch, so that it can be applied to child branches, along with any modifications to the child branch. My questions then: for the trunk, the rotation matrix - is that just the identity matrix * initial orientation vector ? for the first branch (and subsequent branches) - I'll "inherit" the rotation matrix of the parent branch, and apply x and z rotations to that also. e.g. using glm::normalize; using glm::rotateX; using glm::vec4; using glm::mat4; using glm::rotate; vec4 vYAxis = vec4(0.0f, 1.0f, 0.0f, 0.0f); vec4 vInitial = normalize( rotateX( vYAxis, 10.0f ) ); mat4 mRotation = mat4(1.0); // trunk rotation matrix = identity * initial orientation vector mRotation *= vInitial; // first branch = parent rotation matrix * this branches rotations mRotation *= rotate( 10.0f, 1.0f, 0.0f, 0.0f ); // x rotation mRotation *= rotate( 10.0f, 0.0f, 0.0f, 1.0f ); // z rotation Are my maths and approach correct, or am I completely wrong? Finally, I'm using the glm library with OpenGL / C++ for this. Is the order of x rotation and z rotation important?

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• Alternatives to Pessimistic Locking in Cluster Applications

  - by amphibient

  I am researching alternatives to database-level pessimistic locking to achieve transaction isolation in a cluster of Java applications going against the same database. Synchronizing concurrent access in the application tier is clearly not a solution in the present configuration because the same database transaction can be invoked from multiple JVMs concurrently. Currently, we are subject to occasional race conditions which, due to the optimistic locking we have in place via Hibernate, cause a StaleObjectStateException exception and data loss. I have a moderately large transaction within the scope of my refactoring project. Let's describe it as updating one top-level table row and then making various related inserts and/or updates to several of its child entities. I would like to insure exclusive access to the top-level table row and all of the children to be affected but I would like to stay away from pessimistic locking at the database level for performance reasons mostly. We use Hibernate for ORM. Does it make sense to start a single (perhaps synchronous) message queue application into which this method could be moved to insure synchronized access as opposed to each cluster node using its own, which is a clear race condition hazard? I am mentioning this approach even though I am not confident in it because both the top-level table row and its children could also be updated from other system calls, not just the mentioned transaction. So I am seeking to design a solution where the top-level table row and its children will all somehow be pseudo-locked (exclusive transaction isolation) but at the application and not the database level. I am open to ideas and suggestions, I understand this is not a very cut and dried challenge.

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• Go/Obj-C style interfaces with ability to extend compiled objects after initial release

  - by Skrylar

  I have a conceptual model for an object system which involves combining Go/Obj-C interfaces/protocols with being able to add virtual methods from any unit, not just the one which defines a class. The idea of this is to allow Ruby-ish open classes so you can take a minimalist approach to library development, and attach on small pieces of functionality as is actually needed by the whole program. Implementation of this involves a table of methods marked virtual in an RTTI table, which system functions are allowed to add to during module initialization. Upon typecasting an object to an interface, a Go-style lookup is done to create a vtable for that particular mapping and pass it off so you can have comparable performance to C/C++. In this case, methods may be added /afterwards/ which were not previously known and these new methods allow newer interfaces to be satisfied; while I like this idea because it seems like it would be very flexible (disregarding the potential for spaghetti code, which can happen with just about any model you use regardless). By wrapping the system calls for binding methods up in a set of clean C-compatible calls, one would also be able to integrate code with shared libraries and retain a decent amount of performance (Go does not do shared linking, and Objective-C does a dynamic lookup on each call.) Is there a valid use-case for this model that would make it worth the extra background plumbing? As much as this Dylan-style extensibility would be nice to have access to, I can't quite bring myself to a use case that would justify the overhead other than "it could make some kinds of code more extensible in future scenarios."

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• Personalized Pricing

  - by David Dorf

  In past postings I've spent a fair amount of time talking about targeted promotions.  Using a complete view of the customer that includes purchase history, location history, and psychographics gleaned from social media, we can select the offer with the greatest chance of redemption.  This is done to influence shopping behavior, which might be introducing the consumer to a new product line, increasing their basket size, increasing frequency of purchases, etc. Safeway seems to be taking a slightly different approach with their personalized pricing.  In additional to offering electronic coupons and club card offers, they are also providing a personalized price for certain items based on purchase history.  So when Sally want to shop at Safeway, she first checks the "Just for U" website for three types of deals.  She starts by selecting manufacturer coupons to load into her loyalty card, then she checks the Club Card for offers like "buy one get one free." The third step is the interesting one.  Safeway will set a particular lower price for Sally good for 90 days on items she buys often.  Clearly this isn't enforcing a new behavior but rather instilling loyalty.  I would love to know exactly how they are determining the personalized price.  Of course bargain hunters can still stack the three offers so they can, for example, get their $4.99 Oatmeal for $0.72. I like this particular question and answer from their website's FAQ: My offers are not that great. Can I tell you what offers I need? That's a good idea. That functionality is not currently available, but we appreciate your input and are constantly improving our just for U program. Stay tuned for exciting enhancements! I suppose if Safeway is tracking all the purchases, they can easily determine whether the customer if profitable.  As long as the customer stays profitable, why not let them determine a few offers themselves?  Food for thought.

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• Simplest way to render image over top of another with another image used as mask in OpenGL?

  - by Adam Naylor

  The effect I'm looking for is to have a single large background image that is always visible (at full alpha) and then show a second image (what I call a light map or specular map) that is partially shown over the top based on a third image (which is effectively a mask). The effect is similar to this effect except instead of simply darkening or lightening the background image using the third image it needs to mask the second without effecting the first at all. The third image is the only one that moves therefore hard baking the third images alpha into the second image isn't an option. If my explanation isn't clear I'll provide visual examples when I have more time. I'd prefer not to go down a shader route as I haven't taught myself this area yet so unless I have too I'd rather try to achieve this with simple alpha blending. Happy to use a shader approach. Cheers. Additional These third images are obviously light sources being cast onto the first image showing the specular information from the second image to simulate the light 'shining' off the objects in the first image. The solution I implement will need to allow two light sources to potentially overlap so my current thoughts are that the alpha values of the two images will need to be combined (Added?) to produce a final image which masks the second image? Don't worry about things like coloured lights. For this technique the lights are all considered white.

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• Where to place the R code for R+Sweave+LaTeX workflow

  - by claytontstanley

  I spent the last week learning 3 new tools: R, Sweave, and LaTeX. One question that came to my mind though when working through my first project: Where do I place the majority of the R code? The tutorials that I read online placed the majority of the R code in the LaTeX .Rnw file. However, I find having a bunch of R calculations in the LaTeX file distracting. What I do find extremely helpful (of course) is to call out to R code in the LaTeX file and embed the result. So the workflow I've been using is to place 99% of my R code in my .R file. I run that file first, save a bunch of calculations as objects, and output the .Rout file once finished (to save the work). Then when running Sweave, I load up that .Rout file, so that I have the majority of my calculations already completed and in the Sweave R session. Then my LaTeX callouts to R are quite simple: Just give me the XTable stored in 'res.table', or give me the result of an already-computed calculation stored in the variable 'res'. So I push towards the minimal amount of R code in the LaTex file possible, to achieve the desired result (embedding stats results in the LaTeX writeup). Does anyone have any experience with this approach? I'm just worried I might run into trouble further down the line, when I start really trying to load up and leverage this workflow.

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• How would you TDD the functionality of getting the corresponding process of a running windows service?

  - by Matt Spinelli

  Purpose Over the last year or more I've been learning unit testing via books I've read recently like The Art of Unit Testing, Working Effectively with Legacy Code, and others. I've also been using unit tests, mocking frameworks, and the like, periodically at work and definitely see the value. However, I'm still having a hard time wrapping my mind around TDD (as opposed to TAD) when the situation calls for code that is gong to mostly use external API calls. Problem to solve Get the process associated with a windows service using the service name. example: Function GetProcess(ByVal serviceName As String) As Process Rules Show each major iteration in production & test code using TDD No need to see any other code or configuration that is required to get things to run. Just curious about the interfaces, concrete classes, and test methods. C# or VB.NET Must use the .Net framework regarding services/processes (i.e. System.Diagnostics.Process) Test Frameworks: Nunit or MSTest Isolation Frameworks: Moq, Rhino Mock, or Microsoft Moles Must write true unit tests (no integration tests) Additional notes As far as I can tell there are two approaches design wise. Use an Inversion of Control approach along with using the Adapter and/or Facade patterns to wrap the underlying .net framework objects dealing with processes and services. Keep the .net framework code in the class containing the Get Process method and use code detouring (interception) via Microsoft Moles to isolate the hard dependencies from the method under test.

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• Recovering data from /

  - by Abhijit Gavas

  I accidentally installed Ubuntu to one of my data drives from Windows. The drive was a NTFS drive and contained about 80 GB of important data. The size of the drive is 110 GB. Its new file system is ext4. In an attempt to recover the data, I downloaded foremost and tried the following commands: foremost -i / -o /media/281C8DB01C8D7998/Recovery/ -T -v foremost -i /dev/sda7 -o /media/281C8DB01C8D7998/Recovery/ -T -v (sda7 is the drive in question.) It appears that with either command, foremost gets stuck reading some file. Here is the console output: abhi@abi-PC:/dev$ foremost -i /dev/sda7 -o /media/281C8DB01C8D7998/Recovery/ -T -v Foremost version 1.5.7 by Jesse Kornblum, Kris Kendall, and Nick Mikus Audit File Foremost started at Fri Sep 28 20:58:00 2012 Invocation: foremost -i /dev/sda7 -o /media/281C8DB01C8D7998/Recovery/ -T -v Output directory: /media/281C8DB01C8D7998/Recovery_Fri_Sep_28_20_58_00_2012 Configuration file: /etc/foremost.conf Processing: stdin |------------------------------------------------------------------ File: stdin Start: Fri Sep 28 20:58:00 2012 Length: Unknown Num Name (bs=512) Size File Offset Comment Killed As you can see I have to kill it from system monitor. This approach does not seem to be working. What else could I try to recover the files? Please help. The files are very important and I will be devastated if I cannot recover them.

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