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  • Construction Paper, Legos, and Architectural Modeling

    I can remember as a kid playing with construction paper and Legos to explore my imagination. Through my exploration I was able to build airplanes, footballs, guns, and more, out of paper. Additionally I could create entire cities, robots, or anything else I could image out of Legos.  These toys, I now realize were in fact tools that gave me an opportunity to explore my ideas in the physical world through the use of modeling.  My imagination was allowed to run wild as I, unknowingly at the time, made design decisions that directly affected the models I was building from the raw materials.  To prove my point further, I can remember building a paper airplane that seemed to go nowhere when I tried to throw it. So I decided to attach a paper clip to the plane before I decided to throw it the next time to test my concept that by adding more weight to the plane that it would fly better and for longer distances. The paper airplane allowed me to model my design decision through the use of creating an artifact in that I created a paper airplane that was carrying extra weight through the incorporation of the paper clip in to the design. Also, I remember using Legos to build all sorts of creations, and these creations became artifacts of my imagination. As I further and further defined my Lego creations through the process of playing I was able to create elaborate artifacts of my imagination. These artifacts represented design decision I had made in the evolution of my creation through my child like design process. In some form or fashion the artifacts I created as a kid are very similar to the artifacts that I create when I model a software architectural concept or a software design in that the process of making decisions is directly translated in to a tangible model in the form of an architectural model. Architectural models have been defined as artifacts that depict design decisions of a system’s architecture.  The act of creating architectural models is the act of architectural modeling. Furthermore, architectural modeling is the process of creating a physical model based architectural concepts and documenting these design decisions. In the process of creating models, the standard notation used is Architectural modeling notation. This notation is the primary method of capturing the essence of design decisions regarding architecture.  Modeling notations can vary based on the need and intent of a project; typically they range from natural language to a diagram based notation. Currently, Unified Markup Language (UML) is the industry standard in terms of architectural modeling notation  because allows for architectures to be defined through a series of boxes, lines, arrows and other basic symbols that encapsulate design designs in to virtual components, connectors, configurations and interfaces.  Furthermore UML allows for additional break down of models through the use of natural language as to explain each section of the model in plain English. One of the major factors in architectural modeling is to define what is to be modeled. As a basic rule of thumb, I tend to model architecture based on the complexity of systems or sub sub-systems of architecture. Another key factor is the level of detail that is actually needed for a model. For example if I am modeling a system for a CEO to view then the low level details will be omitted. In comparison, if I was modeling a system for another engineer to actually implement I would include as much detailed information as I could to help the engineer implement my design.

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  • Apps UX Launches Blueprints for Mobile User Experiences

    - by mvaughan
    By Misha Vaughan, Oracle Applications User ExperienceAt Oracle OpenWorld 2012 this year, the Oracle Applications User Experience (Apps UX) team announced the release of Mobile User Experience Functional Design Patterns. These patterns are designed to work directly with Oracle’s Fusion Middleware, specifically, ADF Mobile.  The Oracle Application Development Framework for mobile users enables developers to build one application that can be deployed to multiple mobile device platforms. These same mobile design patterns provide the guidance for Oracle teams to develop Fusion Mobile expenses. Application developers can use Oracle’s mobile design patterns to design iPhone, Android, or browser-based smartphone applications. We are sharing our mobile design patterns and their baked-in, scientifically proven usability to enable Oracle customers and partners to build mobile applications quickly.A different way of thinking and designing. Lynn Rampoldi-Hnilo, Senior Manager of Mobile User Experiences for Apps UX, says mobile design has to be compelling. “It needs to be optimized for the device, and be visually rich and simple,” she said. “What is really key is that you are designing for a user’s most personal device, the device that they will have with them at all times of the day.”Katy Massucco, director of the overall design patterns site, said: “You need to start with a simplified task flow. Everything should be a natural interaction. The action should be relevant and leveraging the device. It should be seamless.”She suggests that developers identify the essential tasks that a user would want to do while mobile. “They need to understand the user and the context,” she added. ?A sample inline action design patternWhat people are sayingReactions to the release of the design patterns have been positive. Debra Lilley, Oracle ACE Director and Fusion User Experience Advocate (FXA), has already demo’ed Fusion Mobile Expenses widely.  Fellow Oracle Ace Director Ronald van Luttikhuizen, called it a “cool demo by @debralilley of the new mobile expenses app.” FXA member Floyd Teter says he is already cooking up some plans for using mobile design patterns.  We hope to see those ideas at Collaborate or ODTUG in 2013. For another perspective on why user experience is such an important focus for mobile applications, check out this video by John King, Director, and Monty Latiolais, President, both from ODTUG, or the Oracle Development Tools User Group.In a separate interview by e-mail, Latiolais wrote: “I enjoy the fact we can take something that, in the past, has been largely subjective, and now apply to it a scientifically proven look and feel. Trusting Oracle’s UX Design Patterns, the presentation really can become one less thing to worry about. As someone with limited ADF experience, that is extremely beneficial.”?King, who was also interviewed by e-mail, wrote: “User Experience is about making the task at hand as easy and error-free as possible. Oracle's UX labs worked hard to make the User Experience in the new Fusion Applications as good as possible; ADF makes adding tested, consistent, user experiences a declarative exercise by leveraging that work. As we move applications onto mobile platforms, user experience is the driving factor. Customers are "spoiled" by a bevy of fantastic applications, and ours cannot disappoint them. Creating applications that enable users to quickly and effectively accomplish whatever task is at hand takes thought and practice. Developers must become ’power users’ and then create applications that they and their users will love.”

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  • Could I be going crazy with Event Handlers? Am I going the "wrong way" with my design?

    - by sensae
    I guess I've decided that I really like event handlers. I may be suffering a bit from analysis paralysis, but I'm concerned about making my design unwieldy or running into some other unforeseen consequence to my design decisions. My game engine currently does basic sprite-based rendering with a panning overhead camera. My design looks a bit like this: SceneHandler Contains a list of classes that implement the SceneListener interface (currently only Sprites). Calls render() once per tick, and sends onCameraUpdate(); messages to SceneListeners. InputHandler Polls the input once per tick, and sends a simple "onKeyPressed" message to InputListeners. I have a Camera InputListener which holds a SceneHandler instance and triggers updateCamera(); events based on what the input is. AgentHandler Calls default actions on any Agents (AI) once per tick, and will check a stack for any new events that are registered, dispatching them to specific Agents as needed. So I have basic sprite objects that can move around a scene and use rudimentary steering behaviors to travel. I've gotten onto collision detection, and this is where I'm not sure the direction my design is going is good. Is it a good practice to have many, small event handlers? I imagine going the way I am that I'd have to implement some kind of CollisionHandler. Would I be better off with a more consolidated EntityHandler which handles AI, collision updates, and other entity interactions in one class? Or will I be fine just implementing many different event handling subsystems which pass messages to each other based on what kind of event it is? Should I write an EntityHandler which is simply responsible for coordinating all these sub event handlers? I realize in some cases, such as my InputHandler and SceneHandler, those are very specific types of events. A large portion of my game code won't care about input, and a large portion won't care about updates that happen purely in the rendering of the scene. Thus I feel my isolation of those systems is justified. However, I'm asking this question specifically approaching game logic type events.

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  • Issue with VS 2008 designer and usercontrol.

    - by Ram
    Hello, I have created a custom data grid control. I dragged it on windows form and set its properties like column and all & ran the project. It built successfully and I am able to view the grid control on the form. Now if i try to view that form in designer, I am getting following error.. Object reference not set to an instance of an object. Instances of this error (1) 1. Hide Call Stack at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.GetMemberTargetObject(XmlElementData xmlElementData, String& member) at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.CreateAssignStatement(XmlElementData xmlElement) at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.XmlElementData.get_CodeDomElement() at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.EndElement(String prefix, String name, String urn) at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.Parse(XmlReader reader) at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.ParseXml(String xmlStream, CodeStatementCollection statementCollection, String fileName, String methodName) at Microsoft.VisualStudio.Design.Serialization.CodeDom.VSCodeDomParser.OnMethodPopulateStatements(Object sender, EventArgs e) at System.CodeDom.CodeMemberMethod.get_Statements() at System.ComponentModel.Design.Serialization.TypeCodeDomSerializer.Deserialize(IDesignerSerializationManager manager, CodeTypeDeclaration declaration) at System.ComponentModel.Design.Serialization.CodeDomDesignerLoader.PerformLoad(IDesignerSerializationManager manager) at Microsoft.VisualStudio.Design.Serialization.CodeDom.VSCodeDomDesignerLoader.PerformLoad(IDesignerSerializationManager serializationManager) at Microsoft.VisualStudio.Design.Serialization.CodeDom.VSCodeDomDesignerLoader.DeferredLoadHandler.Microsoft.VisualStudio.TextManager.Interop.IVsTextBufferDataEvents.OnLoadCompleted(Int32 fReload) If I ignore the exception, form appears blank with no sign of grid control on it. However I can see the code for the grid in the designer file. Any pointer on this would be a great help.

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  • VS 2008 designer and usercontrol.

    - by Ram
    Hello, I have created a custom data grid control. I dragged it on windows form and set its properties like column and all & ran the project. It built successfully and I am able to view the grid control on the form. Now if i try to view that form in designer, I am getting following error.. Object reference not set to an instance of an object. Instances of this error (1) 1. Hide Call Stack at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.GetMemberTargetObject(XmlElementData xmlElementData, String& member) at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.CreateAssignStatement(XmlElementData xmlElement) at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.XmlElementData.get_CodeDomElement() at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.EndElement(String prefix, String name, String urn) at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.Parse(XmlReader reader) at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.ParseXml(String xmlStream, CodeStatementCollection statementCollection, String fileName, String methodName) at Microsoft.VisualStudio.Design.Serialization.CodeDom.VSCodeDomParser.OnMethodPopulateStatements(Object sender, EventArgs e) at System.CodeDom.CodeMemberMethod.get_Statements() at System.ComponentModel.Design.Serialization.TypeCodeDomSerializer.Deserialize(IDesignerSerializationManager manager, CodeTypeDeclaration declaration) at System.ComponentModel.Design.Serialization.CodeDomDesignerLoader.PerformLoad(IDesignerSerializationManager manager) at Microsoft.VisualStudio.Design.Serialization.CodeDom.VSCodeDomDesignerLoader.PerformLoad(IDesignerSerializationManager serializationManager) at Microsoft.VisualStudio.Design.Serialization.CodeDom.VSCodeDomDesignerLoader.DeferredLoadHandler.Microsoft.VisualStudio.TextManager.Interop.IVsTextBufferDataEvents.OnLoadCompleted(Int32 fReload) If I ignore the exception, form appears blank with no sign of grid control on it. However I can see the code for the grid in the designer file. Any pointer on this would be a great help. I have customized grid for my custom requirements like I have added custom text box n all. I have defined 3 constructors public GridControl() public GridControl(IContainer container) protected GridControl(SerializationInfo info, StreamingContext context)

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  • transfer database from local machine to hosting server

    - by c11ada
    hey all, im trying to transfer my database from local machine to server, im using the publish to provider wizard in visual web developer to generate a scrip, im then using the generated script on the serever database. i keep getting the following error can some one please tell where im going wrong Msg 468, Level 16, State 9, Procedure aspnet_UsersInRoles_RemoveUsersFromRoles, Line 53 Cannot resolve the collation conflict between "Latin1_General_CI_AS" and "SQL_Latin1_General_CP1_CI_AS" in the equal to operation. Msg 468, Level 16, State 9, Procedure aspnet_UsersInRoles_RemoveUsersFromRoles, Line 58 Cannot resolve the collation conflict between "Latin1_General_CI_AS" and "SQL_Latin1_General_CP1_CI_AS" in the equal to operation. Msg 468, Level 16, State 9, Procedure aspnet_UsersInRoles_RemoveUsersFromRoles, Line 87 Cannot resolve the collation conflict between "Latin1_General_CI_AS" and "SQL_Latin1_General_CP1_CI_AS" in the equal to operation. Msg 468, Level 16, State 9, Procedure aspnet_UsersInRoles_RemoveUsersFromRoles, Line 92 Cannot resolve the collation conflict between "Latin1_General_CI_AS" and "SQL_Latin1_General_CP1_CI_AS" in the equal to operation. Msg 468, Level 16, State 9, Procedure aspnet_UsersInRoles_AddUsersToRoles, Line 48 Cannot resolve the collation conflict between "Latin1_General_CI_AS" and "SQL_Latin1_General_CP1_CI_AS" in the equal to operation. Msg 468, Level 16, State 9, Procedure aspnet_UsersInRoles_AddUsersToRoles, Line 52 Cannot resolve the collation conflict between "Latin1_General_CI_AS" and "SQL_Latin1_General_CP1_CI_AS" in the equal to operation. Msg 468, Level 16, State 9, Procedure aspnet_UsersInRoles_AddUsersToRoles, Line 79 Cannot resolve the collation conflict between "Latin1_General_CI_AS" and "SQL_Latin1_General_CP1_CI_AS" in the equal to operation. Msg 468, Level 16, State 9, Procedure aspnet_UsersInRoles_AddUsersToRoles, Line 83 Cannot resolve the collation conflict between "Latin1_General_CI_AS" and "SQL_Latin1_General_CP1_CI_AS" in the equal to operation. Msg 468, Level 16, State 9, Procedure aspnet_UsersInRoles_AddUsersToRoles, Line 93 Cannot resolve the collation conflict between "Latin1_General_CI_AS" and "SQL_Latin1_General_CP1_CI_AS" in the equal to operation. Msg 15151, Level 16, State 1, Line 1 Cannot find the object 'aspnet_UsersInRoles_AddUsersToRoles', because it does not exist or you do not have permission. Msg 15151, Level 16, State 1, Line 1 Cannot find the object 'aspnet_UsersInRoles_RemoveUsersFromRoles', because it does not exist or you do not have permission. thanks

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  • Where does java.util.logging.Logger store their log

    - by Harry Pham
    This might be a stupid question but I am a bit lost with java Logger private static Logger logger = Logger.getLogger("order.web.OrderManager"); logger.info("Removed order " + id + "."); Where do I see the log? Also this quote from java.util.logging.Logger library: On each logging call the Logger initially performs a cheap check of the request level (e.g. SEVERE or FINE) against the effective log level of the logger. If the request level is lower than the log level, the logging call returns immediately. After passing this initial (cheap) test, the Logger will allocate a LogRecord to describe the logging message. It will then call a Filter (if present) to do a more detailed check on whether the record should be published. If that passes it will then publish the LogRecord to its output Handlers. Does this mean that if I have 3 request level log: logger.log(Level.FINE, "Something"); logger.log(Level.WARNING, "Something"); logger.log(Level.SEVERE, "Something"); And my log level is SEVERE, I can see all three logs, if my log level is WARNING, then I cant see SEVERE log, is that correct? And how do I set the log level?

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  • TableTools only exporting single header row

    - by Rakeesh
    I am using the DataTable jquery plugin from: http://datatables.net/ I have a DataTable that has multi-row table header with colspan. Something like: <thead> <tr> <th>Level 1</th> <th colspan='2'>Level 1 - Item 1</th> <th colspan='2'>Level 1 - Item 2</th> </tr> <tr> <th>Level 2</th> <th>Level 2 - Item 1a</th> <th>Level 2 - Item 1b</th> <th>Level 2 - Item 2a</th> <th>Level 2 - Item 2b</th> </tr> </thead> However when I use the TableTools plugin to export then except for the "Print" option all the rest (Excel, CSV, Pdf etc) only has the "Level 2" header row and not the Level 1. Any suggestions on how to get it to export also Level 1?

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  • Technical Article: Oracle Magazine Java Developer of the Year Adam Bien on Java EE 6 Simplicity by Design

    - by janice.heiss(at)oracle.com
    Java Champion and Oracle Magazine Java Developer of the Year, Adam Bien, offers his unique perspective on how to leverage new Java EE 6 features to build simple and maintainable applications in a new article in Oracle Magazine. Bien examines different Java EE 6 architectures and design approaches in an effort to help developers build efficient, simple, and maintainable applications.From the article: "Java EE 6 consists of a set of independent APIs released together under the Java EE name. Although these APIs are independent, they fit together surprisingly well. For a given application, you could use only JavaServer Faces (JSF) 2.0, you could use Enterprise JavaBeans (EJB) 3.1 for transactional services, or you could use Contexts and Dependency Injection (CDI) with Java Persistence API (JPA) 2.0 and the Bean Validation model to implement transactions.""With a pragmatic mix of available Java EE 6 APIs, you can entirely eliminate the need to implement infrastructure services such as transactions, threading, throttling, or monitoring in your application. The real challenge is in selecting the right subset of APIs that minimizes overhead and complexity while making sure you don't have to reinvent the wheel with custom code. As a general rule, you should strive to use existing Java SE and Java EE services before expanding your search to find alternatives." Read the entire article here.

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  • How to design highly scalable web services in Java?

    - by Kshitiz Sharma
    I am creating some Web Services that would have 2000 concurrent users. The services are offered for free and are hence expected to get a large user base. In the future it may be required to scale up to 50,000 users. There are already a few other questions that address the issue like - Building highly scalable web services However my requirements differ from the question above. For example - My application does not have a user interface, so images, CSS, javascript are not an issue. It is in Java so suggestions like using HipHop to translate PHP to native code are useless. Hence I decided to ask my question separately. This is my project setup - Rest based Web services using Apache CXF Hibernate 3.0 (With relevant optimizations like lazy loading and custom HQL for tune up) Tomcat 6.0 MySql 5.5 My questions are - Are there alternatives to Mysql that offer better performance for what I'm trying to do? What are some general things to abide by in order to scale a Java based web application? I am thinking of putting my Application in two tomcat instances with httpd redirecting the request to appropriate tomcat on basis of load. Is this the right approach? Separate tomcat instances can help but then database becomes the bottleneck since both applications access the same database? I am a programmer not a Db Admin, how difficult would it be to cluster a Mysql database (or, to cluster whatever database offered as an alternative to 1)? How effective are caching solutions like EHCache? Any other general best practices? Some clarifications - Could you partition the data? Yes we could but we're trying to avoid it. We need to run a lot of data mining algorithms and the design would evolve over time so we can't be sure what lines of partition should be there.

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  • What is the best approach for database design with lots of columns?

    - by Pratyush
    I am writing a query based financial application. It lets the user to write complicated equations (much like WHERE part of an SQL query) and find companies matching those criteria. For the above, I currently have more than 500 columns in the database table (each column representing a financial field). Example of Columns are: company_name, sales_annual_00, sales_annual_01, sales_annual_02, sales_annual_03, sales_annual_04, protit_annual_00, profit_annual1...(over 500 such columns). The number of rows is around 5000. Going forward, I would like to further increase the number of columns/financial-fields. For the above I would like to get help regarding: 1) What is the best database design approach? Is it ok to have these many number of columns? 2) How can it be normalized? (User can use any of these fields in search criteria). 3) Is it ok to stick with MySQL, or modern document based databases like MongoDB should be better for it? P.S. (Update): I have been using MySQL till now and a running example of the usage is at: http://screener.in/companies/89/Formula-- In above there around 500 fields/columns to create your query on, however, I seek to increase that number to much more in future.

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  • Is this the correct approach to an OOP design structure in php?

    - by Silver89
    I'm converting a procedural based site to an OOP design to allow more easily manageable code in the future and so far have created the following structure: /classes /templates index.php With these classes: ConnectDB Games System User User -Moderator User -Administrator In the index.php file I have code that detects if any $_GET values are posted to determine on which page content to build (it's early so there's only one example and no default): function __autoload($className) { require "classes/".strtolower($className).".class.php"; } $db = new Connect; $db->connect(); $user = new User(); if(isset($_GET['gameId'])) { System::buildGame($gameId); } This then runs the BuildGame function in the system class which looks like the following and then uses gets in the Game Class to return values, such as $game->getTitle() in the template file template/play.php: function buildGame($gameId){ $game = new Game($gameId); $game->setRatio(900, 600); require 'templates/play.php'; } I also have .htaccess so that actual game page url works instead of passing the parameters to index.php Are there any major errors of how I'm setting this up or do I have the general idea of OOP correct?

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  • How does Batcher Merge work at a high level?

    - by Mike
    I'm trying to grasp the concept of a Batcher Sort. However, most resources I've found online focus on proof entirely or on low-level pseudocode. Before I look at proofs, I'd like to understand how Batcher Sort works. Can someone give a high level overview of how Batcher Sort works(particularly the merge) without overly verbose pseudocode(I want to get the idea behind the Batcher Sort, not implement it)? Thanks!

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  • Msg 10054, Level 20, State 0, Line 0 Error when altering a stored procedure to add a couple of curso

    - by doug_w
    We have a home-rolled backup stored procedure that uses xp_cmdshell to create and clean up database backups. We have an instance that is 2005 sp3 that we are trying to deploy this script to. I am at a bit of a loss for why it is not working. When I execute the create it runs for about 30 seconds and yields the following error: Msg 10054, Level 20, State 0, Line 0 A transport-level error has occurred when sending the request to the server. (provider: TCP Provider, error: 0 - An existing connection was forcibly closed by the remote host.) In my tinkering I discovered that by removing the cursors that actually do the work it will allow me to create the stored procedure (not very helpful for me though). If I add the cursors back in using an alter the error returns. I would be curious if someone has experienced this problem and knows of a solution or work around. I am not opposed to posting the source, it is just lengthy. Things I have checked: Error Logs No dump files in the log directory Thanks in advance for the help.

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  • What are good or interesting Assembler-like languages, but at a higher level?

    - by CodexArcanum
    I've been looking at L.in.oleum and am intrigued by it's mix of higher-level constructs (loops, dynamic variables) with low-level assembler power (registers). Are there other languages like Lino out there, which blend the speed of assembler with productivity enhancing features? EDIT: I realized this kind of sounds like an ad. I'm genuinely interested in other assembler-like languages, Lino is just the only one I happen to know of.

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  • Does running a SQL Server 2005 database in compatibility level 80 have a negative impact on performa

    - by Templar
    Our software must be able to run on SQL Server 2000 and 2005. To simplify development, we're running our SQL Server 2005 databases in compatibility level 80. However, database performance seems slower on SQL 2005 than on SQL 2000 in some cases (we have not confirmed this using benchmarks yet). Would upgrading the compatibility level to 90 improve performance on the SQL 2005 servers?

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  • How to create a level with curved lines with cocos2d + Box2d on the iphone?

    - by Steven
    I'd like to create a game that has levels such as this: http://img169.imageshack.us/img169/7294/picdq.png The Player moves "flies" through the level and mustn't collide with the walls. How can I create such levels? I found that piece of software: http://www.sapusmedia.com/levelsvg/ It's not that cheap, so I wonder whether there is another way to create such a level as shown in the picture above...?

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  • Sharepoint - how to set permission level to add item but not view?

    - by Stuart
    I want to allow a certain group of users to add items to a list, but not be able to view all items. This is so I can set up a workflow with certain parts of it private. I thought it'd be possible by defining a new permission level in: http://servername/_layouts/addrole.aspx ('Add a permission level' page) However, when you select the "add items" list permission, "view items" is automatically ticked also. Anyone know a solution to this?

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  • Using low level api for datastore in google app engine ? is it bad ?

    - by Chez
    There is little documentation on how to use the low level api for datastore and quite a lot on JPA and JDO and how it translates to it. My question is: is there any advantage in coding against the JPA or JDO specs instead of accessing directly the low level api for datastore ? From an initial look, it seems simple and straight forward but I am not sure if there are good reasons why not to do it. Thanks Cx

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  • Which Cassandra API provides the highest level of abstraction?

    - by knorv
    There are a lot of Cassandra API:s available and usually the programming language preference determines the choice of API. However, if we take the programming language component out of the equation, what Cassandra API provides the highest level of abstraction? Definition of "level of abstraction" in this context: An API providing a lot of extra goodies such as index handling, etc would be considered being at a higher abstraction layer than a bare bones "close to Thrift" API.

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  • Back to Basics: When does a .NET Assembly Dependency get loaded

    - by Rick Strahl
    When we work on typical day to day applications, it's easy to forget some of the core features of the .NET framework. For me personally it's been a long time since I've learned about some of the underlying CLR system level services even though I rely on them on a daily basis. I often think only about high level application constructs and/or high level framework functionality, but the low level stuff is often just taken for granted. Over the last week at DevConnections I had all sorts of low level discussions with other developers about the inner workings of this or that technology (especially in light of my Low Level ASP.NET Architecture talk and the Razor Hosting talk). One topic that came up a couple of times and ended up a point of confusion even amongst some seasoned developers (including some folks from Microsoft <snicker>) is when assemblies actually load into a .NET process. There are a number of different ways that assemblies are loaded in .NET. When you create a typical project assemblies usually come from: The Assembly reference list of the top level 'executable' project The Assembly references of referenced projects Dynamically loaded at runtime via AppDomain/Reflection loading In addition .NET automatically loads mscorlib (most of the System namespace) the boot process that hosts the .NET runtime in EXE apps, or some other kind of runtime hosting environment (runtime hosting in servers like IIS, SQL Server or COM Interop). In hosting environments the runtime host may also pre-load a bunch of assemblies on its own (for example the ASP.NET host requires all sorts of assemblies just to run itself, before ever routing into your user specific code). Assembly Loading The most obvious source of loaded assemblies is the top level application's assembly reference list. You can add assembly references to a top level application and those assembly references are then available to the application. In a nutshell, referenced assemblies are not immediately loaded - they are loaded on the fly as needed. So regardless of whether you have an assembly reference in a top level project, or a dependent assembly assemblies typically load on an as needed basis, unless explicitly loaded by user code. The same is true of dependent assemblies. To check this out I ran a simple test: I have a utility assembly Westwind.Utilities which is a general purpose library that can work in any type of project. Due to a couple of small requirements for encoding and a logging piece that allows logging Web content (dependency on HttpContext.Current) this utility library has a dependency on System.Web. Now System.Web is a pretty large assembly and generally you'd want to avoid adding it to a non-Web project if it can be helped. So I created a Console Application that loads my utility library: You can see that the top level Console app a reference to Westwind.Utilities and System.Data (beyond the core .NET libs). The Westwind.Utilities project on the other hand has quite a few dependencies including System.Web. I then add a main program that accesses only a simple utillity method in the Westwind.Utilities library that doesn't require any of the classes that access System.Web: static void Main(string[] args) { Console.WriteLine(StringUtils.NewStringId()); Console.ReadLine(); } StringUtils.NewStringId() calls into Westwind.Utilities, but it doesn't rely on System.Web. Any guesses what the assembly list looks like when I stop the code on the ReadLine() command? I'll wait here while you think about it… … … So, when I stop on ReadLine() and then fire up Process Explorer and check the assembly list I get: We can see here that .NET has not actually loaded any of the dependencies of the Westwind.Utilities assembly. Also not loaded is the top level System.Data reference even though it's in the dependent assembly list of the top level project. Since this particular function I called only uses core System functionality (contained in mscorlib) there's in fact nothing else loaded beyond the main application and my Westwind.Utilities assembly that contains the method accessed. None of the dependencies of Westwind.Utilities loaded. If you were to open the assembly in a disassembler like Reflector or ILSpy, you would however see all the compiled in dependencies. The referenced assemblies are in the dependency list and they are loadable, but they are not immediately loaded by the application. In other words the C# compiler and .NET linker are smart enough to figure out the dependencies based on the code that actually is referenced from your application and any dependencies cascading down into the dependencies from your top level application into the referenced assemblies. In the example above the usage requirement is pretty obvious since I'm only calling a single static method and then exiting the app, but in more complex applications these dependency relationships become very complicated - however it's all taken care of by the compiler and linker figuring out what types and members are actually referenced and including only those assemblies that are in fact referenced in your code or required by any of your dependencies. The good news here is: That if you are referencing an assembly that has a dependency on something like System.Web in a few places that are not actually accessed by any of your code or any dependent assembly code that you are calling, that assembly is never loaded into memory! Some Hosting Environments pre-load Assemblies The load behavior can vary however. In Console and desktop applications we have full control over assembly loading so we see the core CLR behavior. However other environments like ASP.NET for example will preload referenced assemblies explicitly as part of the startup process - primarily to minimize load conflicts. Specifically ASP.NET pre-loads all assemblies referenced in the assembly list and the /bin folder. So in Web applications it definitely pays to minimize your top level assemblies if they are not used. Understanding when Assemblies Load To clarify and see it actually happen what I described in the first example , let's look at a couple of other scenarios. To see assemblies loading at runtime in real time lets create a utility function to print out loaded assemblies to the console: public static void PrintAssemblies() { var assemblies = AppDomain.CurrentDomain.GetAssemblies(); foreach (var assembly in assemblies) { Console.WriteLine(assembly.GetName()); } } Now let's look at the first scenario where I have class method that references internally uses System.Web. In the first scenario lets add a method to my main program like this: static void Main(string[] args) { Console.WriteLine(StringUtils.NewStringId()); Console.ReadLine(); PrintAssemblies(); } public static void WebLogEntry() { var entry = new WebLogEntry(); entry.UpdateFromRequest(); Console.WriteLine(entry.QueryString); } UpdateFromWebRequest() internally accesses HttpContext.Current to read some information of the ASP.NET Request object so it clearly needs a reference System.Web to work. In this first example, the method that holds the calling code is never called, but exists as a static method that can potentially be called externally at some point. What do you think will happen here with the assembly loading? Will System.Web load in this example? No - it doesn't. Because the WebLogEntry() method is never called by the mainline application (or anywhere else) System.Web is not loaded. .NET dynamically loads assemblies as code that needs it is called. No code references the WebLogEntry() method and so System.Web is never loaded. Next, let's add the call to this method, which should trigger System.Web to be loaded because a dependency exists. Let's change the code to: static void Main(string[] args) { Console.WriteLine(StringUtils.NewStringId()); Console.WriteLine("--- Before:"); PrintAssemblies(); WebLogEntry(); Console.WriteLine("--- After:"); PrintAssemblies(); Console.ReadLine(); } public static void WebLogEntry() { var entry = new WebLogEntry(); entry.UpdateFromRequest(); Console.WriteLine(entry.QueryString); } Looking at the code now, when do you think System.Web will be loaded? Will the before list include it? Yup System.Web gets loaded, but only after it's actually referenced. In fact, just until before the call to UpdateFromRequest() System.Web is not loaded - it only loads when the method is actually called and requires the reference in the executing code. Moral of the Story So what have we learned - or maybe remembered again? Dependent Assembly References are not pre-loaded when an application starts (by default) Dependent Assemblies that are not referenced by executing code are never loaded Dependent Assemblies are just in time loaded when first referenced in code All of this is nothing new - .NET has always worked like this. But it's good to have a refresher now and then and go through the exercise of seeing it work in action. It's not one of those things we think about everyday, and as I found out last week, I couldn't remember exactly how it worked since it's been so long since I've learned about this. And apparently I'm not the only one as several other people I had discussions with in relation to loaded assemblies also didn't recall exactly what should happen or assumed incorrectly that just having a reference automatically loads the assembly. The moral of the story for me is: Trying at all costs to eliminate an assembly reference from a component is not quite as important as it's often made out to be. For example, the Westwind.Utilities module described above has a logging component, including a Web specific logging entry that supports pulling information from the active HTTP Context. Adding that feature requires a reference to System.Web. Should I worry about this in the scope of this library? Probably not, because if I don't use that one class of nearly a hundred, System.Web never gets pulled into the parent process. IOW, System.Web only loads when I use that specific feature and if I am, well I clearly have to be running in a Web environment anyway to use it realistically. The alternative would be considerably uglier: Pulling out the WebLogEntry class and sticking it into another assembly and breaking up the logging code. In this case - definitely not worth it. So, .NET definitely goes through some pretty nifty optimizations to ensure that it loads only what it needs and in most cases you can just rely on .NET to do the right thing. Sometimes though assembly loading can go wrong (especially when signed and versioned local assemblies are involved), but that's subject for a whole other post…© Rick Strahl, West Wind Technologies, 2005-2012Posted in .NET  CSharp   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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