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  • Why lock statements don't scale

    - by Alex.Davies
    We are going to have to stop using lock statements one day. Just like we had to stop using goto statements. The problem is similar, they're pretty easy to follow in small programs, but code with locks isn't composable. That means that small pieces of program that work in isolation can't necessarily be put together and work together. Of course actors scale fine :) Why lock statements don't scale as software gets bigger Deadlocks. You have a program with lots of threads picking up lots of locks. You already know that if two of your threads both try to pick up a lock that the other already has, they will deadlock. Your program will come to a grinding halt, and there will be fire and brimstone. "Easy!" you say, "Just make sure all the threads pick up the locks in the same order." Yes, that works. But you've broken composability. Now, to add a new lock to your code, you have to consider all the other locks already in your code and check that they are taken in the right order. Algorithm buffs will have noticed this approach means it takes quadratic time to write a program. That's bad. Why lock statements don't scale as hardware gets bigger Memory bus contention There's another headache, one that most programmers don't usually need to think about, but is going to bite us in a big way in a few years. Locking needs exclusive use of the entire system's memory bus while taking out the lock. That's not too bad for a single or dual-core system, but already for quad-core systems it's a pretty large overhead. Have a look at this blog about the .NET 4 ThreadPool for some numbers and a weird analogy (see the author's comment). Not too bad yet, but I'm scared my 1000 core machine of the future is going to go slower than my machine today! I don't know the answer to this problem yet. Maybe some kind of per-core work queue system with hierarchical work stealing. Definitely hardware support. But what I do know is that using locks specifically prevents any solution to this. We should be abstracting our code away from the details of locks as soon as possible, so we can swap in whatever solution arrives when it does. NAct uses locks at the moment. But my advice is that you code using actors (which do scale well as software gets bigger). And when there's a better way of implementing actors that'll scale well as hardware gets bigger, only NAct needs to work out how to use it, and your program will go fast on it's own.

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  • Microsoft Introduces WebMatrix

    - by Rick Strahl
    originally published in CoDe Magazine Editorial Microsoft recently released the first CTP of a new development environment called WebMatrix, which along with some of its supporting technologies are squarely aimed at making the Microsoft Web Platform more approachable for first-time developers and hobbyists. But in the process, it also provides some updated technologies that can make life easier for existing .NET developers. Let’s face it: ASP.NET development isn’t exactly trivial unless you already have a fair bit of familiarity with sophisticated development practices. Stick a non-developer in front of Visual Studio .NET or even the Visual Web Developer Express edition and it’s not likely that the person in front of the screen will be very productive or feel inspired. Yet other technologies like PHP and even classic ASP did provide the ability for non-developers and hobbyists to become reasonably proficient in creating basic web content quickly and efficiently. WebMatrix appears to be Microsoft’s attempt to bring back some of that simplicity with a number of technologies and tools. The key is to provide a friendly and fully self-contained development environment that provides all the tools needed to build an application in one place, as well as tools that allow publishing of content and databases easily to the web server. WebMatrix is made up of several components and technologies: IIS Developer Express IIS Developer Express is a new, self-contained development web server that is fully compatible with IIS 7.5 and based on the same codebase that IIS 7.5 uses. This new development server replaces the much less compatible Cassini web server that’s been used in Visual Studio and the Express editions. IIS Express addresses a few shortcomings of the Cassini server such as the inability to serve custom ISAPI extensions (i.e., things like PHP or ASP classic for example), as well as not supporting advanced authentication. IIS Developer Express provides most of the IIS 7.5 feature set providing much better compatibility between development and live deployment scenarios. SQL Server Compact 4.0 Database access is a key component for most web-driven applications, but on the Microsoft stack this has mostly meant you have to use SQL Server or SQL Server Express. SQL Server Compact is not new-it’s been around for a few years, but it’s been severely hobbled in the past by terrible tool support and the inability to support more than a single connection in Microsoft’s attempt to avoid losing SQL Server licensing. The new release of SQL Server Compact 4.0 supports multiple connections and you can run it in ASP.NET web applications simply by installing an assembly into the bin folder of the web application. In effect, you don’t have to install a special system configuration to run SQL Compact as it is a drop-in database engine: Copy the small assembly into your BIN folder (or from the GAC if installed fully), create a connection string against a local file-based database file, and then start firing SQL requests. Additionally WebMatrix includes nice tools to edit the database tables and files, along with tools to easily upsize (and hopefully downsize in the future) to full SQL Server. This is a big win, pending compatibility and performance limits. In my simple testing the data engine performed well enough for small data sets. This is not only useful for web applications, but also for desktop applications for which a fully installed SQL engine like SQL Server would be overkill. Having a local data store in those applications that can potentially be accessed by multiple users is a welcome feature. ASP.NET Razor View Engine What? Yet another native ASP.NET view engine? We already have Web Forms and various different flavors of using that view engine with Web Forms and MVC. Do we really need another? Microsoft thinks so, and Razor is an implementation of a lightweight, script-only view engine. Unlike the Web Forms view engine, Razor works only with inline code, snippets, and markup; therefore, it is more in line with current thinking of what a view engine should represent. There’s no support for a “page model” or any of the other Web Forms features of the full-page framework, but just a lightweight scripting engine that works with plain markup plus embedded expressions and code. The markup syntax for Razor is geared for minimal typing, plus some progressive detection of where a script block/expression starts and ends. This results in a much leaner syntax than the typical ASP.NET Web Forms alligator (<% %>) tags. Razor uses the @ sign plus standard C# (or Visual Basic) block syntax to delineate code snippets and expressions. Here’s a very simple example of what Razor markup looks like along with some comment annotations: <!DOCTYPE html> <html>     <head>         <title></title>     </head>     <body>     <h1>Razor Test</h1>          <!-- simple expressions -->     @DateTime.Now     <hr />     <!-- method expressions -->     @DateTime.Now.ToString("T")          <!-- code blocks -->     @{         List<string> names = new List<string>();         names.Add("Rick");         names.Add("Markus");         names.Add("Claudio");         names.Add("Kevin");     }          <!-- structured block statements -->     <ul>     @foreach(string name in names){             <li>@name</li>     }     </ul>           <!-- Conditional code -->        @if(true) {                        <!-- Literal Text embedding in code -->        <text>         true        </text>;    }    else    {        <!-- Literal Text embedding in code -->       <text>       false       </text>;    }    </body> </html> Like the Web Forms view engine, Razor parses pages into code, and then executes that run-time compiled code. Effectively a “page” becomes a code file with markup becoming literal text written into the Response stream, code snippets becoming raw code, and expressions being written out with Response.Write(). The code generated from Razor doesn’t look much different from similar Web Forms code that only uses script tags; so although the syntax may look different, the operational model is fairly similar to the Web Forms engine minus the overhead of the large Page object model. However, there are differences: -Razor pages are based on a new base class, Microsoft.WebPages.WebPage, which is hosted in the Microsoft.WebPages assembly that houses all the Razor engine parsing and processing logic. Browsing through the assembly (in the generated ASP.NET Temporary Files folder or GAC) will give you a good idea of the functionality that Razor provides. If you look closely, a lot of the feature set matches ASP.NET MVC’s view implementation as well as many of the helper classes found in MVC. It’s not hard to guess the motivation for this sort of view engine: For beginning developers the simple markup syntax is easier to work with, although you obviously still need to have some understanding of the .NET Framework in order to create dynamic content. The syntax is easier to read and grok and much shorter to type than ASP.NET alligator tags (<% %>) and also easier to understand aesthetically what’s happening in the markup code. Razor also is a better fit for Microsoft’s vision of ASP.NET MVC: It’s a new view engine without the baggage of Web Forms attached to it. The engine is more lightweight since it doesn’t carry all the features and object model of Web Forms with it and it can be instantiated directly outside of the HTTP environment, which has been rather tricky to do for the Web Forms view engine. Having a standalone script parser is a huge win for other applications as well – it makes it much easier to create script or meta driven output generators for many types of applications from code/screen generators, to simple form letters to data merging applications with user customizability. For me personally this is very useful side effect and who knows maybe Microsoft will actually standardize they’re scripting engines (die T4 die!) on this engine. Razor also better fits the “view-based” approach where the view is supposed to be mostly a visual representation that doesn’t hold much, if any, code. While you can still use code, the code you do write has to be self-contained. Overall I wouldn’t be surprised if Razor will become the new standard view engine for MVC in the future – and in fact there have been announcements recently that Razor will become the default script engine in ASP.NET MVC 3.0. Razor can also be used in existing Web Forms and MVC applications, although that’s not working currently unless you manually configure the script mappings and add the appropriate assemblies. It’s possible to do it, but it’s probably better to wait until Microsoft releases official support for Razor scripts in Visual Studio. Once that happens, you can simply drop .cshtml and .vbhtml pages into an existing ASP.NET project and they will work side by side with classic ASP.NET pages. WebMatrix Development Environment To tie all of these three technologies together, Microsoft is shipping WebMatrix with an integrated development environment. An integrated gallery manager makes it easy to download and load existing projects, and then extend them with custom functionality. It seems to be a prominent goal to provide community-oriented content that can act as a starting point, be it via a custom templates or a complete standard application. The IDE includes a project manager that works with a single project and provides an integrated IDE/editor for editing the .cshtml and .vbhtml pages. A run button allows you to quickly run pages in the project manager in a variety of browsers. There’s no debugging support for code at this time. Note that Razor pages don’t require explicit compilation, so making a change, saving, and then refreshing your page in the browser is all that’s needed to see changes while testing an application locally. It’s essentially using the auto-compiling Web Project that was introduced with .NET 2.0. All code is compiled during run time into dynamically created assemblies in the ASP.NET temp folder. WebMatrix also has PHP Editing support with syntax highlighting. You can load various PHP-based applications from the WebMatrix Web Gallery directly into the IDE. Most of the Web Gallery applications are ready to install and run without further configuration, with Wizards taking you through installation of tools, dependencies, and configuration of the database as needed. WebMatrix leverages the Web Platform installer to pull the pieces down from websites in a tight integration of tools that worked nicely for the four or five applications I tried this out on. Click a couple of check boxes and fill in a few simple configuration options and you end up with a running application that’s ready to be customized. Nice! You can easily deploy completed applications via WebDeploy (to an IIS server) or FTP directly from within the development environment. The deploy tool also can handle automatically uploading and installing the database and all related assemblies required, making deployment a simple one-click install step. Simplified Database Access The IDE contains a database editor that can edit SQL Compact and SQL Server databases. There is also a Database helper class that facilitates database access by providing easy-to-use, high-level query execution and iteration methods: @{       var db = Database.OpenFile("FirstApp.sdf");     string sql = "select * from customers where Id > @0"; } <ul> @foreach(var row in db.Query(sql,1)){         <li>@row.FirstName @row.LastName</li> } </ul> The query function takes a SQL statement plus any number of positional (@0,@1 etc.) SQL parameters by simple values. The result is returned as a collection of rows which in turn have a row object with dynamic properties for each of the columns giving easy (though untyped) access to each of the fields. Likewise Execute and ExecuteNonQuery allow execution of more complex queries using similar parameter passing schemes. Note these queries use string-based queries rather than LINQ or Entity Framework’s strongly typed LINQ queries. While this may seem like a step back, it’s also in line with the expectations of non .NET script developers who are quite used to writing and using SQL strings in code rather than using OR/M frameworks. The only question is why was something not included from the beginning in .NET and Microsoft made developers build custom implementations of these basic building blocks. The implementation looks a lot like a DataTable-style data access mechanism, but to be fair, this is a common approach in scripting languages. This type of syntax that uses simple, static, data object methods to perform simple data tasks with one line of code are common in scripting languages and are a good match for folks working in PHP/Python, etc. Seems like Microsoft has taken great advantage of .NET 4.0’s dynamic typing to provide this sort of interface for row iteration where each row has properties for each field. FWIW, all the examples demonstrate using local SQL Compact files - I was unable to get a SQL Server connection string to work with the Database class (the connection string wasn’t accepted). However, since the code in the page is still plain old .NET, you can easily use standard ADO.NET code or even LINQ or Entity Framework models that are created outside of WebMatrix in separate assemblies as required. The good the bad the obnoxious - It’s still .NET The beauty (or curse depending on how you look at it :)) of Razor and the compilation model is that, behind it all, it’s still .NET. Although the syntax may look foreign, it’s still all .NET behind the scenes. You can easily access existing tools, helpers, and utilities simply by adding them to the project as references or to the bin folder. Razor automatically recognizes any assembly reference from assemblies in the bin folder. In the default configuration, Microsoft provides a host of helper functions in a Microsoft.WebPages assembly (check it out in the ASP.NET temp folder for your application), which includes a host of HTML Helpers. If you’ve used ASP.NET MVC before, a lot of the helpers should look familiar. Documentation at the moment is sketchy-there’s a very rough API reference you can check out here: http://www.asp.net/webmatrix/tutorials/asp-net-web-pages-api-reference Who needs WebMatrix? Uhm… good Question Clearly Microsoft is trying hard to create an environment with WebMatrix that is easy to use for newbie developers. The goal seems to be simplicity in providing a minimal development environment and an easy-to-use script engine/language that makes it easy to get started with. There’s also some focus on community features that can be used as starting points, such as Web Gallery applications and templates. The community features in particular are very nice and something that would be nice to eventually see in Visual Studio as well. The question is whether this is too little too late. Developers who have been clamoring for a simpler development environment on the .NET stack have mostly left for other simpler platforms like PHP or Python which are catering to the down and dirty developer. Microsoft will be hard pressed to win those folks-and other hardcore PHP developers-back. Regardless of how much you dress up a script engine fronted by the .NET Framework, it’s still the .NET Framework and all the complexity that drives it. While .NET is a fine solution in its breadth and features once you get a basic handle on the core features, the bar of entry to being productive with the .NET Framework is still pretty high. The MVC style helpers Microsoft provides are a good step in the right direction, but I suspect it’s not enough to shield new developers from having to delve much deeper into the Framework to get even basic applications built. Razor and its helpers is trying to make .NET more accessible but the reality is that in order to do useful stuff that goes beyond the handful of simple helpers you still are going to have to write some C# or VB or other .NET code. If the target is a hobby/amateur/non-programmer the learning curve isn’t made any easier by WebMatrix it’s just been shifted a tad bit further along in your development endeavor when you run out of canned components that are supplied either by Microsoft or the community. The database helpers are interesting and actually I’ve heard a lot of discussion from various developers who’ve been resisting .NET for a really long time perking up at the prospect of easier data access in .NET than the ridiculous amount of code it takes to do even simple data access with raw ADO.NET. It seems sad that such a simple concept and implementation should trigger this sort of response (especially since it’s practically trivial to create helpers like these or pick them up from countless libraries available), but there it is. It also shows that there are plenty of developers out there who are more interested in ‘getting stuff done’ easily than necessarily following the latest and greatest practices which are overkill for many development scenarios. Sometimes it seems that all of .NET is focused on the big life changing issues of development, rather than the bread and butter scenarios that many developers are interested in to get their work accomplished. And that in the end may be WebMatrix’s main raison d'être: To bring some focus back at Microsoft that simpler and more high level solutions are actually needed to appeal to the non-high end developers as well as providing the necessary tools for the high end developers who want to follow the latest and greatest trends. The current version of WebMatrix hits many sweet spots, but it also feels like it has a long way to go before it really can be a tool that a beginning developer or an accomplished developer can feel comfortable with. Although there are some really good ideas in the environment (like the gallery for downloading apps and components) which would be a great addition for Visual Studio as well, the rest of the development environment just feels like crippleware with required functionality missing especially debugging and Intellisense, but also general editor support. It’s not clear whether these are because the product is still in an early alpha release or whether it’s simply designed that way to be a really limited development environment. While simple can be good, nobody wants to feel left out when it comes to necessary tool support and WebMatrix just has that left out feeling to it. If anything WebMatrix’s technology pieces (which are really independent of the WebMatrix product) are what are interesting to developers in general. The compact IIS implementation is a nice improvement for development scenarios and SQL Compact 4.0 seems to address a lot of concerns that people have had and have complained about for some time with previous SQL Compact implementations. By far the most interesting and useful technology though seems to be the Razor view engine for its light weight implementation and it’s decoupling from the ASP.NET/HTTP pipeline to provide a standalone scripting/view engine that is pluggable. The first winner of this is going to be ASP.NET MVC which can now have a cleaner view model that isn’t inconsistent due to the baggage of non-implemented WebForms features that don’t work in MVC. But I expect that Razor will end up in many other applications as a scripting and code generation engine eventually. Visual Studio integration for Razor is currently missing, but is promised for a later release. The ASP.NET MVC team has already mentioned that Razor will eventually become the default MVC view engine, which will guarantee continued growth and development of this tool along those lines. And the Razor engine and support tools actually inherit many of the features that MVC pioneered, so there’s some synergy flowing both ways between Razor and MVC. As an existing ASP.NET developer who’s already familiar with Visual Studio and ASP.NET development, the WebMatrix IDE doesn’t give you anything that you want. The tools provided are minimal and provide nothing that you can’t get in Visual Studio today, except the minimal Razor syntax highlighting, so there’s little need to take a step back. With Visual Studio integration coming later there’s little reason to look at WebMatrix for tooling. It’s good to see that Microsoft is giving some thought about the ease of use of .NET as a platform For so many years, we’ve been piling on more and more new features without trying to take a step back and see how complicated the development/configuration/deployment process has become. Sometimes it’s good to take a step - or several steps - back and take another look and realize just how far we’ve come. WebMatrix is one of those reminders and one that likely will result in some positive changes on the platform as a whole. © Rick Strahl, West Wind Technologies, 2005-2010Posted in ASP.NET   IIS7  

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  • The View-Matrix and Alternative Calculations

    - by P. Avery
    I'm working on a radiosity processor in DirectX 9. The process requires that the camera be placed at the center of a mesh face and a 'screenshot' be taken facing 5 different directions...forward...up...down...left...right... ...The problem is that when the mesh face is facing up( look vector: 0, 1, 0 )...a view matrix cannot be determined using standard trigonometry functions: Matrix4 LookAt( Vector3 eye, Vector3 target, Vector3 up ) { // The "look-at" vector. Vector3 zaxis = normal(target - eye); // The "right" vector. Vector3 xaxis = normal(cross(up, zaxis)); // The "up" vector. Vector3 yaxis = cross(zaxis, xaxis); // Create a 4x4 orientation matrix from the right, up, and at vectors Matrix4 orientation = { xaxis.x, yaxis.x, zaxis.x, 0, xaxis.y, yaxis.y, zaxis.y, 0, xaxis.z, yaxis.z, zaxis.z, 0, 0, 0, 0, 1 }; // Create a 4x4 translation matrix by negating the eye position. Matrix4 translation = { 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, -eye.x, -eye.y, -eye.z, 1 }; // Combine the orientation and translation to compute the view matrix return ( translation * orientation ); } The above function comes from http://3dgep.com/?p=1700... ...Is there a mathematical approach to this problem? Edit: A problem occurs when setting the view matrix to up or down directions, here is an example of the problem when facing down: D3DXVECTOR4 vPos( 3, 3, 3, 1 ), vEye( 1.5, 3, 3, 1 ), vLook( 0, -1, 0, 1 ), vRight( 1, 0, 0, 1 ), vUp( 0, 0, 1, 1 ); D3DXMATRIX mV, mP; D3DXMatrixPerspectiveFovLH( &mP, D3DX_PI / 2, 1, 0.5f, 2000.0f ); D3DXMatrixIdentity( &mV ); memcpy( ( void* )&mV._11, ( void* )&vRight, sizeof( D3DXVECTOR3 ) ); memcpy( ( void* )&mV._21, ( void* )&vUp, sizeof( D3DXVECTOR3 ) ); memcpy( ( void* )&mV._31, ( void* )&vLook, sizeof( D3DXVECTOR3 ) ); memcpy( ( void* )&mV._41, ( void* )&(-vEye), sizeof( D3DXVECTOR3 ) ); D3DXVec4Transform( &vPos, &vPos, &( mV * mP ) ); Results: vPos = D3DXVECTOR3( 1.5, -6, -0.5, 0 ) - this vertex is not properly processed by shader as the homogenous w value is 0 it cannot be normalized to a position within device space...

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  • New Options for MySQL High Availability

    - by Mat Keep
    Data is the currency of today’s web, mobile, social, enterprise and cloud applications. Ensuring data is always available is a top priority for any organization – minutes of downtime will result in significant loss of revenue and reputation. There is not a “one size fits all” approach to delivering High Availability (HA). Unique application attributes, business requirements, operational capabilities and legacy infrastructure can all influence HA technology selection. And then technology is only one element in delivering HA – “People and Processes” are just as critical as the technology itself. For this reason, MySQL Enterprise Edition is available supporting a range of HA solutions, fully certified and supported by Oracle. MySQL Enterprise HA is not some expensive add-on, but included within the core Enterprise Edition offering, along with the management tools, consulting and 24x7 support needed to deliver true HA. At the recent MySQL Connect conference, we announced new HA options for MySQL users running on both Linux and Solaris: - DRBD for MySQL - Oracle Solaris Clustering for MySQL DRBD (Distributed Replicated Block Device) is an open source Linux kernel module which leverages synchronous replication to deliver high availability database applications across local storage. DRBD synchronizes database changes by mirroring data from an active node to a standby node and supports automatic failover and recovery. Linux, DRBD, Corosync and Pacemaker, provide an integrated stack of mature and proven open source technologies. DRBD Stack: Providing Synchronous Replication for the MySQL Database with InnoDB Download the DRBD for MySQL whitepaper to learn more, including step-by-step instructions to install, configure and provision DRBD with MySQL Oracle Solaris Cluster provides high availability and load balancing to mission-critical applications and services in physical or virtualized environments. With Oracle Solaris Cluster, organizations have a scalable and flexible solution that is suited equally to small clusters in local datacenters or larger multi-site, multi-cluster deployments that are part of enterprise disaster recovery implementations. The Oracle Solaris Cluster MySQL agent integrates seamlessly with MySQL offering a selection of configuration options in the various Oracle Solaris Cluster topologies. Putting it All Together When you add MySQL Replication and MySQL Cluster into the HA mix, along with 3rd party solutions, users have extensive choice (and decisions to make) to deliver HA services built on MySQL To make the decision process simpler, we have also published a new MySQL HA Solutions Guide. Exploring beyond just the technology, the guide presents a methodology to select the best HA solution for your new web, cloud and mobile services, while also discussing the importance of people and process in ensuring service continuity. This is subject recently presented at Oracle Open World, and the slides are available here. Whatever your uptime requirements, you can be sure MySQL has an HA solution for your needs Please don't hesitate to let us know of your HA requirements in the comments section of this blog. You can also contact MySQL consulting to learn more about their HA Jumpstart offering which will help you scope out your scaling and HA requirements.

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  • SQL SERVER – How to easily work with Database Diagrams

    - by Pinal Dave
    Databases are very widely used in the modern world. Regardless of the complexity of a database, each one requires in depth designing. To practice along please Download dbForge Studio now.  The right methodology of designing a database is based on the foundations of data normalization, according to which we should first define database’s key elements – entities. Afterwards the attributes of entities and relations between them are determined. There is a strong opinion that the process of database designing should start with a pencil and a blank sheet of paper. This might look old-fashioned nowadays, because SQL Server provides a much wider functionality for designing databases – Database Diagrams. When using SSMS for working with Database Diagrams I realized two things – on the one hand, visualization of a scheme allows designing a database more efficiently; on the other – when it came to creating a big scheme, some difficulties occurred when designing with SSMS. The alternatives haven’t taken long to wait and dbForge Studio for SQL Server is one of them. Its functions offer more advantages for working with Database Diagrams. For example, unlike SSMS, dbForge Studio supports an opportunity to drag-and-drop several tables at once from the Database Explorer. This is my opinion but personally I find this option very useful. Another great thing is that a diagram can be saved as both a graphic file and a special XML file, which in case of identical environment can be easily opened on the other server for continuing the work. During working with dbForge Studio it turned out that it offers a wide set of elements to operate with on the diagram. Noteworthy among such elements are containers which allow aggregating diagram objects into thematic groups. Moreover, you can even place an image directly on the diagram if the scheme design is based on a standard template. Each of the development environments has a different approach to storing a diagram (for example, SSMS stores them on a server-side, whereas dbForge Studio – in a local file). I haven’t found yet an ability to convert existing diagrams from SSMS to dbForge Studio. However I hope Devart developers will implement this feature in one of the following releases. All in all, editing Database Diagrams through dbForge Studio was a nice experience and allowed speeding-up the common database designing tasks. Download dbForge Studio now. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL Utility, T SQL

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  • Teacher demands excessive/unjustified use of Design Patterns

    - by SoboLAN
    I study computer science and I have a class called "Programming Techniques". Its purpose is to teach (us) good object oriented design principles. During the semester we have homeworks, programs that we must write to demonstrate what we've learned. The lab assistant demands for each of these homeworks that specific design patterns should be used. For example, the current homework is an application used for processing customer orders. We are demanded to use either "Factory Method" or "Abstract Factory" design patterns for this. It gets even worse: at the end of the semester we must write a program (something more complex) that must use at least one creational pattern, at least one structural pattern and at least one behavioural pattern. Is it normal to demand this ? I mean, forcing us to design our programs in such a way that a specific design pattern makes sense is just beyond what I consider ok. If I'm a car mechanic and have a huge tool box, then I will use a certain tool from that box if and when the situation demands it. Not more, not less. If my design of the application doesn't demand at all the use of "Abstract Factory" (for example), then why should I implement it ? I'm not sure yet if the senior lecturer agrees with what the lab assistant is demanding, but I want to talk to him about it and I need solid arguments to do so. How should I approach this problem with him ? PS: I'm sure there must be a better way to teach us these things. Maybe making us each week read about 3 design patterns and the next week giving us a test with small but specific programming or architectural situations/problems. The goal in that test would be to identify what design patterns would make sense and how they could be implemented. This way, he can see if we understand them. EDIT: These homeworks are not just 100-line programs, they have quite a lot of requirements and are fairly complicated. This is the reason we have about 2 - 3 weeks of deadline for each of them. I agree that practicing this is the best way to learn. But shouldn't smaller programs/applications be used for this ? Something just for demonstrating purposes. Not big programs with lots of requirements/classes/etc.

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  • In the Cloud, Everything Costs Money

    - by BuckWoody
    I’ve been teaching my daughter about budgeting. I’ve explained that most of the time the money coming in is from only one or two sources – and you can only change that from time to time. The money going out, however, is to many locations, and it changes all the time. She’s made a simple debits and credits spreadsheet, and I’m having her research each part of the budget. Her eyes grow wide when she finds out everything has a cost – the house, gas for the lawnmower, dishes, water for showers, food, electricity to run the fridge, a new fridge when that one breaks, everything has a cost. She asked me “how do you pay for all this?” It’s a sentiment many adults have looking at their own budgets – and one reason that some folks don’t even make a budget. It’s hard to face up to the realities of how much it costs to do what we want to do. When we design a computing solution, it’s interesting to set up a similar budget, because we don’t always consider all of the costs associated with it. I’ve seen design sessions where the new software or servers are considered, but the “sunk” costs of personnel, networking, maintenance, increased storage, new sizes for backups and offsite storage and so on are not added in. They are already on premises, so they are assumed to be paid for already. When you move to a distributed architecture, you'll see more costs directly reflected. Store something, pay for that storage. If the system is deployed and no one is using it, you’re still paying for it. As you watch those costs rise, you might be tempted to think that a distributed architecture costs more than an on-premises one. And you might be right – for some solutions. I’ve worked with a few clients where moving to a distributed architecture doesn’t make financial sense – so we didn’t implement it. I still designed the system in a distributed fashion, however, so that when it does make sense there isn’t much re-architecting to do. In other cases, however, if you consider all of the on-premises costs and compare those accurately to operating a system in the cloud, the distributed system is much cheaper. Again, I never recommend that you take a “here-or-there-only” mentality – I think a hybrid distributed system is usually best – but each solution is different. There simply is no “one size fits all” to architecting a solution. As you design your solution, cost out each element. You might find that using a hybrid approach saves you money in one design and not in another. It’s a brave new world indeed. So yes, in the cloud, everything costs money. But an on-premises solution also costs money – it’s just that “dad” (the company) is paying for it and we don’t always see it. When we go out on our own in the cloud, we need to ensure that we consider all of the costs.

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  • Amazon.com Cutting Off Colorado Affiliates

    - by Joe Mayo
    I received an email from Amazon.com today, essentially cutting off my affiliate status because I'm in Colorado. Colorado recently passed legislation that requires retailers to either collect sales tax for on-line transactions or engage in an onerous process that makes you wish you had collected sales tax.  After I Tweeted this, Mike Jones tweeted a link to the legislation.  Here's an excerpt from Amazon.com's email: "Dear Colorado-based Amazon Associate: We are writing from the Amazon Associates Program to inform you that the Colorado government recently enacted a law to impose sales tax regulations on online retailers. The regulations are burdensome and no other state has similar rules. The new regulations do not require online retailers to collect sales tax. Instead, they are clearly intended to increase the compliance burden to a point where online retailers will be induced to "voluntarily" collect Colorado sales tax -- a course we won't take. We and many others strongly opposed this legislation, known as HB 10-1193, but it was enacted anyway. Regrettably, as a result of the new law, we have decided to stop advertising through Associates based in Colorado. We plan to continue to sell to Colorado residents, however, and will advertise through other channels, including through Associates based in other states. There is a right way for Colorado to pursue its revenue goals, but this new law is a wrong way. As we repeatedly communicated to Colorado legislators, including those who sponsored and supported the new law, we are not opposed to collecting sales tax within a constitutionally-permissible system applied even-handedly. The US Supreme Court has defined what would be constitutional, and if Colorado would repeal the current law or follow the constitutional approach to collection, we would welcome the opportunity to reinstate Colorado-based Associates. You may express your views of Colorado's new law to members of the General Assembly and to Governor Ritter, who signed the bill. Your Associates account has been closed as of March 8, 2010, and we will no longer pay advertising fees for customers you refer to Amazon.com after that date. Please be assured that all qualifying advertising fees earned prior to March 8, 2010, will be processed and paid in accordance with our regular payment schedule. Based on your account closure date of March 8, any final payments will be paid by May 31, 2010. We have enjoyed working with you and other Colorado-based participants in the Amazon Associates Program, and wish you all the best in your future.   Best Regards,   The Amazon Associates Team"

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  • Viewing at Impossible Angles

    - by kemer
    The picture of the little screwdriver with the Allen wrench head to the right is bound to invoke a little nostalgia for those readers who were Sun customers in the late 80s. This tool was a very popular give-away: it was essential for installing and removing Multibus (you youngsters will have to look that up on Wikipedia…) cards in our systems. Back then our mid-sized systems were gargantuan: it was routine for us to schlep around a 200 lb. desk side box and 90 lb. monitor to demo a piece of software your smart phone will run better today. We were very close to the hardware, and the first thing a new field sales systems engineer had to learn was how put together a system. If you were lucky, a grizzled service engineer might run you through the process once, then threaten your health and existence should you ever screw it up so that he had to fix it. Nowadays we make it much easier to learn the ins and outs of our hardware with simulations–3D animations–that take you through the process of putting together or replacing pieces of a system. Most recently, we have posted three sophisticated PDFs that take advantage of Acrobat 9 features to provide a really intelligent approach to documenting hardware installation and repair: Sun Fire X4800/X4800 M2 Animations for Chassis Components Sun Fire X4800/X4800 M2 Animations for Sub Assembly Module (SAM) Sun Fire X4800/X4800 M2 Animations for CMOD Download one of these documents and take a close look at it. You can view the hardware from any angle, including impossible ones. Each document has a number of procedures, that break down into steps. Click on a procedure, then a step and you will see it animated in the drawing. Of course hardware design has generally eliminated the need for things like our old giveaway tools: components snap and lock in. Often you can replace redundant units while the system is hot, but for heaven’s sake, you’ll want to verify that you can do that before you try it! Meanwhile, we can all look forward to a growing portfolio of these intelligent documents. We would love to hear what you think about them. –Kemer

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  • Announcement: Employee Info Starter Kit (v6.0–ASP.NET MVC Edition) is Released

    - by Mohammad Ashraful Alam
    Originally posted on: http://geekswithblogs.net/joycsharp/archive/2013/06/16/announcement-employee-info-starter-kit-v6.0asp.net-mvc-edition-is-released.aspxAfter a long wait, the next version of Employee Info Starter Kit is released! This starter kit is basically a project template that contains code samples targeting a specific technology, such as ASP.NET Web Form, ASP.NET MVC etc. Since its first release, this open source project gained a huge popularity in the developer community and had 250K+ combined downloads. This starter kit is honored to be placed at the official ASP.NET site, along with other asp.net starter kits, which all are being considered as the “best” ASP.NET coding standards, recommended by Microsoft. EISK is showcased in Microsoft’s Channel 9’s Weekly Show, as well. The ASP.NET MVC Edition of the new version 6.0 bundles most of the greatest and successful platforms, frameworks and technologies together, to enable web developers to learn and build manageable and high performance web applications with rich user experience effectively and quickly. User End Specifications Creating a new employee record Read existing employee records Update an existing employee record Delete existing employee records Role based security model Key Technology Areas ASP.NET MVC 4 Entity Framework 4.3.1 Sql Server Compact Edition 4 Visual Studio 2012 QuickStart Guide Getting started with EISK 6.0 ASP.NET is pretty easy. Once you've Visual Studio 2012 installed, then just follow the steps as provided below: Download the EISK 6.0 MVC version. Extract the file. From the extracted folder, click the solution file "Eisk.MVC-VS2012.sln". Right click the "Eisk.MVC" project node and select "Select set as StartUp Project". Hit Ctrl+F5 and explore! Architectural Overview Overall architecture is based on Model-View-Controller pattern Support for desktop & mobile browsers. Usage of Domain Model, Repository and Unit of Work pattern from Domain Driven Development approach Usage of Data Annotations in model (entity) classes to centralize basic validation mechanism that facilitates DRY principle Usage of IValidatableObject interface in model (entity) classes that isolates custom business logic from application layer Usage of OOP inheritance and Value Object pattern in model (entity) classes that provides reusability in application architecture Usage of View Model, Editor Model pattern that provides mechanism for testable view rendering logic Several helper classes and extension methods to enable developers build application with reduced code If you want to learn more about it in details, just check the following links: Getting Started - Hands on Coding Walkthrough – Technology Stack - Design & Architecture Enjoy!

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  • ACORD LOMA 2010: Building Insurance Companies in the Clouds

    - by [email protected]
    Chuck Johnston, vice president of global strategy and alliances for Oracle Insurance, participated in a featured speaking session at ACORD LOMA 2010. He provides an update on his discussions with insurers at the show and after his presentation. Every year I always make a point of walking the show floor at the ACORD LOMA technology conference to visit with colleagues and competitors, and try to get a feel for which way the industry will move over the next 12 months. Insurers are looking for substance in cloud (computing), trying to mix business with pleasure (monetizing social networks), and expect differentiation through commodity (Software as a Service). The disconnect at this show is that most vendors are still struggling with creating a clear path from Facebook to customer intimacy, SaaS to core cost savings and clouds to ubiquitous presence. Vendors need to find new ways to help insurers find the real value in these potentially disruptive technologies by understanding the changes coming to the insurance business and how these new technologies impact the new insurance business. Oracle's approach to understanding the evolving insurance industry comes from a discussion with our customers in our Insurance CIO Council, where one of our customers suggested we buy an insurance company to really understand our customers. We have decided to do the next best thing and build our own model of an insurance company, Alamere Insurance, that uses the latest technologies to transform its own business. Alamere will never issue an actual policy, but it does give us a framework to consider the impacts of changes in the insurance landscape and how Oracle technology meets the challenge or needs to evolve to help our customers be successful. In preparing for my talk at the conference using Alamere as my organizing theme, I found myself reading actuarial memoranda on CSO table changes and articles on underwriting theory that really made me think about my customer's problems first and foremost, and then how Oracle technology can provide answers. As much as I prefer techno-thrillers and sci-fi novels to actuarial papers for plane reading, I got very excited about the idea of putting myself back in the customer shoes I haven't worn in a decade, and really looking at how Oracle can power the Adaptive Insurance Enterprise. Talking to customers and industry people after the session, the idea of Alamere seemed to excite people and I got a lot of suggestions as to what lines of business we should model and where we should focus first on technology uptake. One customer said to a colleague that Oracle's attempt to "share their pain" was unique among vendors. More about Alamere, and the Adaptive Insurance Enterprise next time. Chuck Johnston is vice president of global strategy and alliances for Oracle Insurance.

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  • The importance of Unit Testing in BI

    - by Davide Mauri
    One of the main steps in the process we internally use to develop a BI solution is the implementation of Unit Test of you BI Data. As you may already know, I’ve create a simple (for now) tool that leverages NUnit to allow us to quickly create Unit Testing without having to resort to use Visual Studio Database Professional: http://queryunit.codeplex.com/ Once you have a tool like this one, you can start also to make sure that your BI solution (DWH and CUBE) is not only structurally sound (I mean, the cube or the report gets processed correctly), but you can also check that the logical integrity of your business rules is enforced. For example let’s say that the customer tell you that they will never create an invoice for a specific product-line in 2010 since that product-line is dismissed and will never be sold again. Ok we know that this in theory is true, but a lot of this business rule effectiveness depends on the fact the people does not do a mistake while inserting new orders/invoices and the ERP used implements a check for this business logic. Unfortunately these last two hypotesis are not always true, so you may find yourself really having some invoices for a product line that doesn’t exists anymore. Maybe this kind of situation in future will be solved using Master Data Management but, meanwhile, how you can give and idea of the data quality to your customers? How can you check that logical integrity of the analytical data you produce is exactly what you expect? Well, Unit Testing of a DWH or a CUBE can be a solution. Once you have defined your test suite, by writing SQL and MDX queries that checks that your data is what you expect to be, if you use NUnit (and QueryUnit does), you can then use a tool like NUnit2Report to create a nice HTML report that can be shipped via email to give information of data quality: In addition to that, since NUnit produces an XML file as a result, you can also import it into a SQL Server Database and then monitor the quality of data over time. I’ll be speaking about this approach (and more in general about how to “engineer” a BI solution) at the next European SQL PASS Adaptive BI Best Practices http://www.sqlpass.org/summit/eu2010/Agenda/ProgramSessions/AdaptiveBIBestPratices.aspx I’ll enjoy discussing with you all about this, so see you there! And remember: “if ain't tested it's broken!” (Sorry I don’t remember how said that in first place :-)) Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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  • Simple Mouse Move Event in F# with Winforms

    - by MarkPearl
    This evening I had the pleasure of reading one of ThomasP’s blog posts on first class events. It was an excellent read, and I thought I would make a brief derivative of his post to explore some of the basics. In Thomas’s post he has a form with an ellipse on it that when he clicks on the ellipse it pops up a message box with the button clicked… awesome. Something that got me on the post though was the code similar to the one below… // React to Mouse Move events on the form let evtMessages = frm.MouseMove |> Event.map (fun mi -> mi.Location.ToString()) |> Event.map (sprintf "Hey, you clicked on the ellipse.\nUsing: %s") |> Event.add (MessageBox.Show >> ignore) The MessageBox is a function with a string passed into it. What if I wanted to rather change a mutable value holder instead, how would the syntax go for that? Immediately the thought came to me of anonymous functions. I’ve used them before to do something like this… let HelloPerson personName = "Hello " + personName |> fun(x) -> Console.WriteLine(x) So using the same approach I adapted the event code to instead of showing a Message Box with a string passed in to it, to rather change the forms header. |> Event.map (sprintf "Your mouse position is %s") |> Event.add(fun(x) -> frm.Text <- x) Okay… it looks a bit weird with the –> x <- syntax, but makes sense and works… The next thing I wanted to do was change Thomas’s code sample from having an ellipse, and reacting to the position of the mouse and click, to rather trigger the event whenever the mouse moved. This simple involved removing some filtering code. Finally I wanted the code to work as a FSharp Project without having to run through the F# interactive. To achieve this I just needed to find out how to trigger the window event loop. This can be achieved with the code below… // Program eventloop while frm.Created do Application.DoEvents()   So lets look at the complete code sample… #light open System open System.Drawing open System.Windows.Forms // Create the main form let frm = new Form(ClientSize=Size(600,400)) // React to Mouse Move events on the form let evtMessages = frm.MouseMove |> Event.map (fun mi -> mi.Location.ToString()) |> Event.map (sprintf "Your mouse position is %s") |> Event.add(fun(x) -> frm.Text <- x) // Show the form frm.Show() // Program eventloop while frm.Created do Application.DoEvents()

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  • Understanding Data Science: Recent Studies

    - by Joe Lamantia
    If you need such a deeper understanding of data science than Drew Conway's popular venn diagram model, or Josh Wills' tongue in cheek characterization, "Data Scientist (n.): Person who is better at statistics than any software engineer and better at software engineering than any statistician." two relatively recent studies are worth reading.   'Analyzing the Analyzers,' an O'Reilly e-book by Harlan Harris, Sean Patrick Murphy, and Marck Vaisman, suggests four distinct types of data scientists -- effectively personas, in a design sense -- based on analysis of self-identified skills among practitioners.  The scenario format dramatizes the different personas, making what could be a dry statistical readout of survey data more engaging.  The survey-only nature of the data,  the restriction of scope to just skills, and the suggested models of skill-profiles makes this feel like the sort of exercise that data scientists undertake as an every day task; collecting data, analyzing it using a mix of statistical techniques, and sharing the model that emerges from the data mining exercise.  That's not an indictment, simply an observation about the consistent feel of the effort as a product of data scientists, about data science.  And the paper 'Enterprise Data Analysis and Visualization: An Interview Study' by researchers Sean Kandel, Andreas Paepcke, Joseph Hellerstein, and Jeffery Heer considers data science within the larger context of industrial data analysis, examining analytical workflows, skills, and the challenges common to enterprise analysis efforts, and identifying three archetypes of data scientist.  As an interview-based study, the data the researchers collected is richer, and there's correspondingly greater depth in the synthesis.  The scope of the study included a broader set of roles than data scientist (enterprise analysts) and involved questions of workflow and organizational context for analytical efforts in general.  I'd suggest this is useful as a primer on analytical work and workers in enterprise settings for those who need a baseline understanding; it also offers some genuinely interesting nuggets for those already familiar with discovery work. We've undertaken a considerable amount of research into discovery, analytical work/ers, and data science over the past three years -- part of our programmatic approach to laying a foundation for product strategy and highlighting innovation opportunities -- and both studies complement and confirm much of the direct research into data science that we conducted. There were a few important differences in our findings, which I'll share and discuss in upcoming posts.

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  • Unit testing in Django

    - by acjohnson55
    I'm really struggling to write effective unit tests for a large Django project. I have reasonably good test coverage, but I've come to realize that the tests I've been writing are definitely integration/acceptance tests, not unit tests at all, and I have critical portions of my application that are not being tested effectively. I want to fix this ASAP. Here's my problem. My schema is deeply relational, and heavily time-oriented, giving my model object high internal coupling and lots of state. Many of my model methods query based on time intervals, and I've got a lot of auto_now_add going on in timestamped fields. So take a method that looks like this for example: def summary(self, startTime=None, endTime=None): # ... logic to assign a proper start and end time # if none was provided, probably using datetime.now() objects = self.related_model_set.manager_method.filter(...) return sum(object.key_method(startTime, endTime) for object in objects) How does one approach testing something like this? Here's where I am so far. It occurs to me that the unit testing objective should be given some mocked behavior by key_method on its arguments, is summary correctly filtering/aggregating to produce a correct result? Mocking datetime.now() is straightforward enough, but how can I mock out the rest of the behavior? I could use fixtures, but I've heard pros and cons of using fixtures for building my data (poor maintainability being a con that hits home for me). I could also setup my data through the ORM, but that can be limiting, because then I have to create related objects as well. And the ORM doesn't let you mess with auto_now_add fields manually. Mocking the ORM is another option, but not only is it tricky to mock deeply nested ORM methods, but the logic in the ORM code gets mocked out of the test, and mocking seems to make the test really dependent on the internals and dependencies of the function-under-test. The toughest nuts to crack seem to be the functions like this, that sit on a few layers of models and lower-level functions and are very dependent on the time, even though these functions may not be super complicated. My overall problem is that no matter how I seem to slice it, my tests are looking way more complex than the functions they are testing.

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  • Closing the Gap: 2012 IOUG Enterprise Data Security Survey

    - by Troy Kitch
    The new survey from the Independent Oracle Users Group (IOUG) titled "Closing the Security Gap: 2012 IOUG Enterprise Data Security Survey," uncovers some interesting trends in IT security among IOUG members and offers recommendations for securing data stored in enterprise databases. "Despite growing threats and enterprise data security risks, organizations that implement appropriate detective, preventive, and administrative safeguards are seeing significant results," finds the report's author, Joseph McKendrick, analyst, Unisphere Research. Produced by Unisphere Research and underwritten by Oracle, the report is based on responses from 350 IOUG members representing a variety of job roles, organization sizes, and industry verticals. Key findings include Corporate budgets increase, but trailing. Though corporate data security budgets are increasing this year, they still have room to grow to reach the previous year’s spending. Additionally, more than half of respondents say their organizations still do not have, or are unaware of, data security plans to help address contingencies as they arise. Danger of unauthorized access. Less than a third of respondents encrypt data that is either stored or in motion, and at the same time, more than three-fifths say they send actual copies of enterprise production data to other sites inside and outside the enterprise. Privileged user misuse. Only about a third of respondents say they are able to prevent privileged users from abusing data, and most do not have, or are not aware of, ways to prevent access to sensitive data using spreadsheets or other ad hoc tools. Lack of consistent auditing. A majority of respondents actively collect native database audits, but there has not been an appreciable increase in the implementation of automated tools for comprehensive auditing and reporting across databases in the enterprise. IOUG RecommendationsThe report's author finds that securing data requires not just the ability to monitor and detect suspicious activity, but also to prevent the activity in the first place. To achieve this comprehensive approach, the report recommends the following. Apply an enterprise-wide security strategy. Database security requires multiple layers of defense that include a combination of preventive, detective, and administrative data security controls. Get business buy-in and support. Data security only works if it is backed through executive support. The business needs to help determine what protection levels should be attached to data stored in enterprise databases. Provide training and education. Often, business users are not familiar with the risks associated with data security. Beyond IT solutions, what is needed is a well-engaged and knowledgeable organization to help make security a reality. Read the IOUG Data Security Survey Now.

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  • ArchBeat Link-o-Rama for December 6, 2012

    - by Bob Rhubart
    Above and Beyond with the A-Team Maybe it's the coffee… If you follow this blog you've probably noticed that I regularly feature posts from members of the Oracle Fusion Middleware Architecture team, otherwise known as the A-Team. One of those bloggers, someone identified only as "fip" who writes on the A-Team SOA blog, went above and beyond on Dec 4, publishing a total of four substantial technical posts in a single day, each one worth a look: Retrieve Performance Data from SOA Infrastructure Database Configure Oracle SOA JMSAdatper to Work with WLS JMS Topics How to Achieve OC4J RMI Load Balancing Using BPEL Performance Statistics to Diagnose Performance Bottlenecks Web Service Example - Part 3: Asynchronous | The Oracle ADF Mobile Blog Part 3 in this series from the Oracle ADF Mobile blog looks at "firing the web service asynchronously and then filling in the UI when it completes." Denis says, "This can be useful when you have data on the device in a local store and want to show that to the user while the application uses lazy loading from a web service to load more data." ADF Mobile - Implementing Reusable Mobile Architecture | Andrejus Baranovskis "Reusability was always a strong part of ADF," says Oracle ACE Director Andrejus Baranovskis. "The same high reusability level is supported now in ADF Mobile." The objective of this post is "to prove technically that [the] reusable architecture concept works for ADF Mobile." Basic is Best | Eric Stephens "The world we live in and enterprises we strive to transform with enterprise architecture are complicated organisms, much like the human body," says Oracle Enterprise Architect Eric Stephens. "But sometimes a simple solution is the best approach...Whatever level of abstraction you are working at, less is more." Selling Federal Enterprise Architecture | Ted McLaughlan "EA must be 'sold' directly to the communities that matter from a coordinated, proactive messaging perspective that takes BOTH the Program-level value drivers AND the broader Agency mission and IT maturity context into consideration, " explains Ted McLaughlan. And that's true for any organization. Avoiding the "I'm Spartacus" Scenario in SOA | Ben Wilcock "This ‘SOA Spartacus’ scenario usually occurs quite soon after SOA is articulated as the primary strategic direction of the programme," says Ben Wilcock, "but before the organisation’s SOA capability is mature enough to understand what is meant by SOA, and how it should be designed and delivered." In such cases, perhaps the "A" in SOA is missing, no? Thought for the Day "It makes me feel guilty that anybody should have such a good time doing what they are supposed to do." — Charles Eames (1907–1978) Source: SoftwareQuotes.com

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  • Advantages and disadvantages of building a single page web application

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

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  • Finding the lowest average Hamming distance when the order of the strings matter

    - by user1049697
    I have a sequence of binary strings that I want to find a match for among a set of longer sequences of binary strings. A match means that the compared sequence gives the lowest average Hamming distance when all elements in the shorter sequence have been matched against a sequence in one of the longer sets. Let me try to explain with an example. I have a set of video frames that have been hashed using a perceptual hashing algorithm so that the video frames that look the same has roughly the same hash. I want to match a short video clip against a set of longer videos, to see if the clip is contained in one of these. This means that I need to find out where the sequence of the hashed frames in the short video has the lowest average Hamming distance when compared with the long videos. The short video is the sub strings Sub1, Sub2 and Sub3, and I want to match them against the hashes of the long videos in Src. The clue here is that the strings need to match in the specific order that they are given in, e.g. that Sub1 always has to match the element before Sub2, and Sub2 always has to match the element before Sub3. In this example it would map thusly: Sub1-Src3, Sub2-Src4 and Sub3-Src5. So the question is this: is there an algorithm for finding the lowest average Hamming distance when the order of the elements compared matter? The naïve approach to compare the substring sequence to every source string won't cut it of course, so I need something that preferably can match a (much) shorter sub string to a set of million of elements. I have looked at MVP-trees, BK-trees and similar, but everything seems to only take into account one binary string and not a sequence of them. Sub1: 100111011111011101 Sub2: 110111000010010100 Sub3: 111111010110101101 Src1: 001011010001010110 Src2: 010111101000111001 Src3: 101111001110011101 Src4: 010111100011010101 Src5: 001111010110111101 Src6: 101011111111010101 I have added a calculation of the examples below. (The Hamming distances aren't correct, but it doesn't matter) **Run 1.** dist(Sub1, Src1) = 8 dist(Sub2, Src2) = 10 dist(Sub3, Src3) = 12 average = 10 **Run 2.** dist(Sub1, Src2) = 10 dist(Sub2, Src3) = 12 dist(Sub3, Src4) = 10 average = 11 **Run 3.** dist(Sub1, Src3) = 7 dist(Sub2, Src4) = 6 dist(Sub3, Src5) = 10 average = 8 **Run 4.** dist(Sub1, Src3) = 10 dist(Sub2, Src4) = 4 dist(Sub3, Src5) = 2 average = 5 So the winner here is sequence 4 with an average distance of 5.

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  • Keep taking the tablets

    - by Roger Hart
    A guest editorial for the SimpleTalk newsletter. So why would Red Gate build an Ipad Game? Is it just because tablet devices are exciting and cool? Ok, maybe a little. Mostly, it was seeing that the best existing tablet and smartphone apps do simple, intuitive things, using simple intuitive interfaces to solve single problems. That's pretty close to what we call our own "intuitively simple" approach to software. Tablets and mobile could be fantastic for us, if we can identify those problems that a tablet device can solve. How do you create THE next tool for a completely new technology? We're glad we don't face that problem every day, but it's pretty exciting when we do. We figure we should learn by doing. We created "MobileFoo" (a Red Gate Company) , we picked up some shiny Apple tech, and got to grips with Objective C, and life in the App Store ecosystem. The result so far is an iPad game: Stacks and Heaps It's Rob and Marine's spin on Snakes and Ladders. Instead of snakes we have unhandled exceptions, a blue screen of death, and other hazards. We wanted something compellingly geeky on mobile, and we're pretty sure we've got it. It's trudging through App Store approval as we speak. but if you want to get an idea of what it is like to switch from .net to Objective C, take a look at Rob's post Android and iOS is quite a culture-change for Windows developers. So to give them a feel for the problems real users might have, we needed some real users - we offered our colleagues subsidised tablets. The only conditions were that they get used at work, and we get the feedback. Seeing tablets around the office is starting to give us some data points: Is typing the bottleneck? Will tablets ever cut it as text-entry devices, and could we fix it? Is mobile working held up by the pain of connecting to work LANs? How about security? Multi-tasking will let tablets do more. They're small, easy to use, almost instant to switch on, and connect by Wi Fi. There's plenty on that list to make a sysadmin twitchy. We'll find out as people spend more time working with these devices, and we'd love to hear what you think about tablet devices too. (comments are filtered, what with the spam)

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  • A Community Cure for a String Splitting Headache

    - by Tony Davis
    A heartwarming tale of dogged perseverance and Community collaboration to solve some SQL Server string-related headaches. Michael J Swart posted a blog this week that had me smiling in recognition and agreement, describing how an inquisitive Developer or DBA deals with a problem. It's a three-step process, starting with discomfort and anxiety; a feeling that one doesn't know as much about one's chosen specialized subject as previously thought. It progresses through a phase of intense research and learning until finally one achieves breakthrough, blessed relief and renewed optimism. In this case, the discomfort was provoked by the mystery of massively high CPU when searching Unicode strings in SQL Server. Michael explored the problem via Stack Overflow, Google and Twitter #sqlhelp, finally leading to resolution and a blog post that shared what he learned. Perfect; except that sometimes you have to be prepared to share what you've learned so far, while still mired in the phase of nagging discomfort. A good recent example of this recently can be found on our own blogs. Despite being a loud advocate of the lightning fast T-SQL-based string splitting techniques, honed to near perfection over many years by Jeff Moden and others, Phil Factor retained a dogged conviction that, in theory, shredding element-based XML using XQuery ought to be even more efficient for splitting a string to create a table. After some careful testing, he found instead that the XML way performed and scaled miserably by comparison. Somewhat subdued, and with a nagging feeling that perhaps he was still missing "something", he posted his findings. What happened next was a joy to behold; the community jumped in to suggest subtle changes in approach, using an attribute-based rather than element-based XML list, and tweaking the XQuery shredding. The result was performance and scalability that surpassed all other techniques. I asked Phil how quickly he would have arrived at the real breakthrough on his own. His candid answer was "never". Both are great examples of the power of Community learning and the latter in particular the importance of being brave enough to parade one's ignorance. Perhaps Jeff Moden will accept the string-splitting gauntlet one more time. To quote the great man: you've just got to love this community! If you've an interesting tale to tell about being helped to a significant breakthrough for a problem by the community, I'd love to hear about it. Cheers, Tony.

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  • Creative, busy Devoxx week

    - by JavaCecilia
    I got back from my first visit to the developer conference Devoxx in Antwerp. I can't describe the vibes of the conference, it was a developer amusement park, hackergartens, fact sessions, comic relief provided by Java Posse, James Bond and endless hallway discussions.All and all - I had a lot of fun, my main mission was to talk about Oracle's main focus for OpenJDK which besides development and bug fixing is making sure the infrastructure is working out for the full community. My focus was not to hang out at night club the Noxx, but that was came included in the package :)The London Java community leaders Ben Evans and Martijn Verburg are leading discussions in the community to lay out the necessary requirements for the infrastructure for build and test in the open. They called a first meeting at JavaOne gathering 25 people, including people from RedHat, IBM and Oracle. The second meeting at Devoxx included 14 participants and had representatives from Oracle and IBM. I hope we really can find a way to collaborate on this, making sure we deliver an efficient infrastructure for all engineers to contribute to OpenJDK with.My home in all of this was the BOF rooms and the sessions there meeting the JUG leaders, talking about OpenJDK infrastructure and celebrating the Duchess Duke Award together with the others. The restaurants in the area was slower than I've ever seen, so I missed out on Trisha Gee's brilliant replay of the workshop "The Problem with Women in IT - an Agile Approach" where she masterly leads the audience (a packed room, 50-50 gender distribution) to solve the problem of including more diversity in the developer community. A tough and sometimes sensitive topic where she manages to keep the discussion objective with a focus of improving the matter from a business perspective. Mattias Karlsson is organizing the Java developer conference Jfokus in Stockholm and was there talking to Andres Almires planning a Hackergarten with a possible inclusion of an OpenJDK bugathon. That would be really cool, especially as the Oracle Stockholm Java development office is just across the water from the Jfokus venue, some of the local JVM engineers will likely attend and assist, even though the bug smashing theme will likely be more starter level build warnings in Swing or langtools than fixing JVM bugs.I was really happy that I managed to catch a seat for the Java Posse live podcast "the Third Presidential Debate" a lot of nerd humor, a lot of beer, a lot of fun :) The new member Chet had a perfect dead pan delivery and now I just have to listen more to the podcasts! Can't get the most perfect joke out of my head, talking about beer "As my father always said: Better a bottle in front of me than a frontal lobotomy" - hilarious :)I attended the sessions delivered by my Stockholm office colleagues Marcus Lagergren (on dynamic languages on the jvm, JavaScript in particular) and Joel Borggrén-Franck (Annotations) and was happy to see the packed room and all the questions raised at the end.There's loads of stuff to write about the event, but just have to pace myself for now. It was a fantastic event, captain Stephan Janssen with crew should be really proud to provide this forum to the developer community!

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  • ArchBeat Link-o-Rama for July 3, 2013

    - by Bob Rhubart
    Industrial SOA Chapter 5: Enterprise Service Bus Enterprise Service Bus, the fifth and latest addition to the Industrial SOA article series, answers some of the most important questions surrounding the use of an ESB. Industrial SOA Chapter 4: SOA Maturity The fourth article in the Industrial SOA series, SOA Maturity offers "an exploration of the fundamentals of applying a factory approach to modern service-oriented software development." Using the Exalytics Summary Advisor and Oracle BI Apps 7.9.6.4 | Mark Rittman Oracle ACE Director Mark Rittman's post revisits "the use of the Summary Advisor, with my BI Apps installation bumped-up to version 7.9.6.4, and the Exalytics environment patched up to 11.1.1.6.9, the latest patch release we’ve applied to that environment." Part 1 - 12c Database and WLS - Overview | Steve Felts Steve Felts shares a handy table that "maps the Oracle 12c Database features supported with various combinations of currently available WLS releases, 11g and 12c Drivers, and 11g and 12c Databases." Developers WebCast: Deploy Highly-Available Custom Services on Your Data Grid Products - July 11 Oracle Coherence Sr. Architect Brian Oliver hosts this free July 11 webcast for developers to show you how to "create and deploy customized, highly-available services for your data grid, and how real-time data processing will allow you to provide unmatched end-user experiences." A checklist for OIM go live | Daniel Gralewski FMW A-Team solution architect Daniel Gralewski's list is intended to complement Oracle Identity Manager. His post "provides tips on a few topics that are not part of the documentation." How Many ODI Master Repositories Should We Have? | Christophe Dupupet FMW solution architect Christophe Dupupet provides a simple along with best practices for the architecture of ODI repositories in a corporate environment. Distinguish EA from enterprise wide solution architecture | John Wu My buddy Tony Meyer, who did a great presentation recently at the Cleveland-area Enterprise Architect / Solution Architect Meet-up, recommends this Toolbox article by John Wu. YouTube: Oracle Fusion Applications Developer Tips If you work with Fusion Applications you'll want to check out the tips and tricks for building extensions, customizations, and integrations now available on the new Oracle Fusion Middleware Developer Relations YouTube channel. The CX Factor: Wooing and wowing customers in the digital age "There was a time when 'customer experience' was limited to what happened to you when you walked into a store, restaurant, or other place of business or when you called a business on the telephone. But that was back when you could still smoke on airplanes." Thought for the Day "If you had to identify, in one word, the reason why the human race has not achieved, and never will achieve, its full potential, that word would be 'meetings.' " — Dave Barry (Born July 3, 1947) Source: brainyquote.com

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  • 0xC0017011 and other error messages - what is the error message text?

    Recently there was a bug raised against BIDS Helper which originated in my Expression Editor control. Thankfully the person that raised it kindly included a screenshot, so I had the error code (HRESULT 0xC0017011) and a stack trace that pointed the finger firmly at my control, but no error message text. The code itself looked fine so I searched on the error code but got no results. I’d expected to get a hit from Books Online with the Integration Services Error and Message Reference topic at the very least, but no joy. There is however a more accurate and definitive reference, namely the header file that defines all these codes dtsmsg.h which you can find at- C:\Program Files (x86)\Microsoft SQL Server\110\SDK\Include\dtsmsg.h Looking the code up in the header file gave me a much more useful error message. //////////////////////////////////////////////////////////////////////////// // The parameter is sensitive // // MessageId: DTS_E_SENSITIVEPARAMVALUENOTALLOWED // // MessageText: // // Accessing value of the parameter variable for the sensitive parameter "%1!s!" is not allowed. Verify that the variable is used properly and that it protects the sensitive information. // #define DTS_E_SENSITIVEPARAMVALUENOTALLOWED ((HRESULT)0xC0017011L) Unfortunately I’d forgotten all about this. By the time I had remembered about it, the person who raised the issue had managed to narrow it down to something to do with having  sensitive parameter. Putting that together with the error message I’d finally found, a quick poke around in the code and I found the new GetSensitiveValue method which seemed to do the trick. The HResult fields are also listed online but it only shows the short error message, and it doesn’t include that all so important HRESULT value itself. So let this be a lesson to you (and me!), if you need to check  SSIS error go straight to the horses mouth - dtsmsg.h. This is particularly true when working with early builds, or CTP releases when we expect the documentation to be a bit behind. There is also a programmatic approach to getting better SSIS error messages. I should to take another look at the error handling in the control, or the way it is hosted in BIDS Helper. I suspect that if I use an implementation of Microsoft.SqlServer.Dts.Runtime.Wrapper.IDTSInfoEvents100 I could catch the error itself and get the full error message text which I could then report back. This would obviously be a better user experience and also make it easier to diagnose any issues like this in the future. See ExprssionEvaluator.cs for an example of this in use in the Expression Editor control.

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  • Tips on ensuring Model Quality

    - by [email protected]
    Given enough data that represents well the domain and models that reflect exactly the decision being optimized, models usually provide good predictions that ensure lift. Nevertheless, sometimes the modeling situation is less than ideal. In this blog entry we explore the problems found in a few such situations and how to avoid them.1 - The Model does not reflect the problem you are trying to solveFor example, you may be trying to solve the problem: "What product should I recommend to this customer" but your model learns on the problem: "Given that a customer has acquired our products, what is the likelihood for each product". In this case the model you built may be too far of a proxy for the problem you are really trying to solve. What you could do in this case is try to build a model based on the result from recommendations of products to customers. If there is not enough data from actual recommendations, you could use a hybrid approach in which you would use the [bad] proxy model until the recommendation model converges.2 - Data is not predictive enoughIf the inputs are not correlated with the output then the models may be unable to provide good predictions. For example, if the input is the phase of the moon and the weather and the output is what car did the customer buy, there may be no correlations found. In this case you should see a low quality model.The solution in this case is to include more relevant inputs.3 - Not enough cases seenIf the data learned does not include enough cases, at least 200 positive examples for each output, then the quality of recommendations may be low. The obvious solution is to include more data records. If this is not possible, then it may be possible to build a model based on the characteristics of the output choices rather than the choices themselves. For example, instead of using products as output, use the product category, price and brand name, and then combine these models.4 - Output leaking into input giving the false impression of good quality modelsIf the input data in the training includes values that have changed or are available only because the output happened, then you will find some strong correlations between the input and the output, but these strong correlations do not reflect the data that you will have available at decision (prediction) time. For example, if you are building a model to predict whether a web site visitor will succeed in registering, and the input includes the variable DaysSinceRegistration, and you learn when this variable has already been set, you will probably see a big correlation between having a Zero (or one) in this variable and the fact that registration was successful.The solution is to remove these variables from the input or make sure they reflect the value as of the time of decision and not after the result is known. 

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