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• Is throwing an error in unpredictable subclass-specific circumstances a violation of LSP?

  - by Motti Strom

  Say, I wanted to create a Java List<String> (see spec) implementation that uses a complex subsystem, such as a database or file system, for its store so that it becomes a simple persistent collection rather than an basic in-memory one. (We're limiting it specifically to a List of Strings for the purposes of discussion, but it could extended to automatically de-/serialise any object, with some help. We can also provide persistent Sets, Maps and so on in this way too.) So here's a skeleton implementation: class DbBackedList implements List<String> { private DbBackedList() {} /** Returns a list, possibly non-empty */ public static getList() { return new DbBackedList(); } public String get(int index) { return Db.getTable().getRow(i).asString(); // may throw DbExceptions! } // add(String), add(int, String), etc. ... } My problem lies with the fact that the underlying DB API may encounter connection errors that are not specified in the List interface that it should throw. My problem is whether this violates Liskov's Substitution Principle (LSP). Bob Martin actually gives an example of a PersistentSet in his paper on LSP that violates LSP. The difference is that his newly-specified Exception there is determined by the inserted value and so is strengthening the precondition. In my case the connection/read error is unpredictable and due to external factors and so is not technically a new precondition, merely an error of circumstance, perhaps like OutOfMemoryError which can occur even when unspecified. In normal circumstances, the new Error/Exception might never be thrown. (The caller could catch if it is aware of the possibility, just as a memory-restricted Java program might specifically catch OOME.) Is this therefore a valid argument for throwing an extra error and can I still claim to be a valid java.util.List (or pick your SDK/language/collection in general) and not in violation of LSP? If this does indeed violate LSP and thus not practically usable, I have provided two less-palatable alternative solutions as answers that you can comment on, see below. Footnote: Use Cases In the simplest case, the goal is to provide a familiar interface for cases when (say) a database is just being used as a persistent list, and allow regular List operations such as search, subList and iteration. Another, more adventurous, use-case is as a slot-in replacement for libraries that work with basic Lists, e.g if we have a third-party task queue that usually works with a plain List: new TaskWorkQueue(new ArrayList<String>()).start() which is susceptible to losing all it's queue in event of a crash, if we just replace this with: new TaskWorkQueue(new DbBackedList()).start() we get a instant persistence and the ability to share the tasks amongst more than one machine. In either case, we could either handle connection/read exceptions that are thrown, perhaps retrying the connection/read first, or allow them to throw and crash the program (e.g. if we can't change the TaskWorkQueue code).

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• Does the SPDY protocol eliminate the need for cookieless domains?

  - by Clint Pachl

  With plain HTTP, cookieless domains were an optimization to avoid unnecessarily sending cookie headers for page resources. However, the SPDY protocol compresses HTTP headers and in some cases eliminates unnecessary headers. My question then is, does SPDY make cookieless domains irrelevant? Furthermore, should the page source and all of its resources be hosted at the same domain in order to optimize a SPDY implementation?

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• Web.NET: A Brief Retrospective

  - by Chris Massey

  It’s been several weeks since I had the pleasure of visiting Milan, and joining 150 enthusiastic web developers for a day of server-side frameworks and JavaScript. Lucky for me, I keep good notes. Overall the day went smoothly, with some solid logistics and very attentiveorganizerss, and an impressively diverse audience drawn by the fact that the event was ambitiously run in English. This was great in that it drew a truly pan-European audience (11 countries were represented on the day, and at least 1 visa had to be procured to get someone there!) It was trouble because, in some cases, it pushed speakers outside their comfort zone. Thankfully, despite a slightly rocky start, every session I attended was very well presented, and the consensus on the day was that the speakers were excellent. While I felt that a lot of the speakers had more that they wanted to cover, the topics were well-chosen, every room constantly had a stack of people in it, and all the sessions were pleasingly focused on code & demos. For all that the language barriers occasionally made networking a little challenging,organizerss Simone & Ugo nailed the logistics. Registration was slick, lunch was plentiful, and session management was great. The very generous Rui was kind enough to showcase a short video about Glimpse in his session, which seemed to go down well (Although the audio in the rooms was a little under-powered). Because I think you might need a mid-week chuckle, here are some out-takes.: And lets not forget the Hackathon. The idea was what having just learned about a stack of interesting technologies, attendees could spend an evening (fuelled by pizza and some good Github beer) hacking something together using them. Unfortunately, after a (great)10-hour day, and in many cases facing international travel in the morning, many of the attendees headed straight for their hotel rooms. This idea could work so beautifully, and I’m excited to see how it pans out in 2013. On top of the slick sessions, getting to finally meet Ugo and Simone in the flesh as a pleasure, as was the serendipitous introduction to the most excellent Rui. They’re all fantastic guys who are passionate about the web, and I’m looking forward to finding opportunities to work with them. Simone & Ugo put on a great event, and I’m excited to see what they do next year.

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• How do you manage frequent software releases to multiple clients?

  - by meeech

  hi we have a cross-platform middleware product which we typically end up customizing/bug fixing on a per client basis. In some cases, providing updates as often as once/twice per week. We have a lot of trouble efficiently managing and releasing the updates to our clients. I've done some digging, but I can't find anything to specifically address this problem. Can anyone share their experiences - how do you deal with this scenario, or do you know of a good software delivery cms? thanks

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• SQL Azure and Trust Services

  - by BuckWoody

  Microsoft is working on a new Windows Azure service called “Trust Services”. Trust Services takes a certificate you upload and uses it to encrypt and decrypt sensitive data in the cloud. Of course, like any security service, there’s a bit more to it than that. I’ll give you a quick overview of how you can use this product to protect data you send to SQL Azure. The primary issue with storing data in the cloud is that you are in an environment that isn’t under your control – in fact, that’s the benefit of being in a distributed computing environment in the first place. On premises you’re able to encrypt data you don’t want anyone else to see, using various methods such as passwords (not very strong) or certificates (stronger). When you use a certificate, it’s vital that you create (or procure) and protect it yourself. When you store data remotely, regardless of IaaS, PaaS or SaaS, you don’t own the machines where the data lives. That means if you use a certificate from the cloud vendor to encrypt the data, you have to trust that the data won’t be accessed by the vendor. In some cases having a signed agreement with the vendor that they won’t access your data is sufficient, in other cases that doesn’t meet the requirements your system has for security. With the new Trust Services service, the basic process is that you use a Portal to create a Trust Server using policies and other controls. You place a X.509 Certificate you create or procure in that server. Using the Software development Kit (SDK), the developer has access to an Application Layer Encryption Framework to set fields of data they want to encrypt. From there, the data can be stored in SQL Azure as a standard field – only it is encrypted before it ever arrives. The portion of the client software that decrypts the data uses the same service, so the authenticated user sees the data if they are allowed to do so. The data remains encrypted “at rest”.  You can learn more about this product and check it out in the SQL Azure labs at Microsoft Codename "Trust Services"

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• How can I convert a 2D bitmap (Used for terrain) to a 2D polygon mesh for collision?

  - by Megadanxzero

  So I'm making an artillery type game, sort of similar to Worms with all the usual stuff like destructible terrain etc... and while I could use per-pixel collision that doesn't give me collision normals or anything like that. Converting it all to a mesh would also mean I could use an existing physics library, which would be better than anything I can make by myself. I've seen people mention doing this by using Marching Squares to get contours in the bitmap, but I can't find anything which mentions how to turn these into a mesh (Unless it refers to a 3D mesh with contour lines defining different heights, which is NOT what I want). At the moment I can get a basic Marching Squares contour which looks something like this (Where the grid-like lines in the background would be the Marching Squares 'cells'): That needs to be interpolated to get a smoother, more accurate result but that's the general idea. I had a couple ideas for how to turn this into a mesh, but many of them wouldn't work in certain cases, and the one which I thought would work perfectly has turned out to be very slow and I've not even finished it yet! Ideally I'd like whatever I end up using to be fast enough to do every frame for cases such as rapidly-firing weapons, or digging tools. I'm thinking there must be some kind of existing algorithm/technique for turning something like this into a mesh, but I can't seem to find anything. I've looked at some things like Delaunay Triangulation, but as far as I can tell that won't correctly handle concave shapes like the above example, and also wouldn't account for holes within the terrain. I'll go through the technique I came up with for comparison and I guess I'll see if anyone has a better idea. First of all interpolate the Marching Squares contour lines, creating vertices from the line ends, and getting vertices where lines cross cell edges (Important). Then, for each cell containing vertices create polygons by using 2 vertices, and a cell corner as the 3rd vertex (Probably the closest corner). Do this for each cell and I think you should have a mesh which accurately represents the original bitmap (Though there will only be polygons at the edges of the bitmap, and large filled in areas in between will be empty). The only problem with this is that it involves lopping through every pixel once for the initial Marching Squares, then looping through every cell (image height + 1 x image width + 1) at least twice, which ends up being really slow for any decently sized image...

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• How long of a trial period do you use with programmers - how quickly can you tell if they are talented and a good fit?

  - by blueberryfields

  It seems most jobs that I've been exposed to come with a 3 month trial period, during which the employer decides whether the employee is doing good enough work, and is a good fit. 3 months seem like overkill to me, for most cases we've known much sooner whether someone wasn't a good fit. How long does it take you, on average, to evaluate whether a newly hired programmer is both talented and a good fit for your team?

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• WPF: How to get the bounds of a control in an automatic layout container, in the container coordinate space

  - by Bart Read

  Googling this the other day, I started to get the impression that this might be annoyingly tricky. You might wonder why this is necessary at all, given that WPF implements layout for you in most cases (except for containers such as Canvas), but trust me, if you're developing custom elements, at some point you're probably going to need it. If you're adding controls to a Canvas you can always use the attached Left, Right, etc., properties to get the bounds. Fortunately it's really no more difficult...(read more)

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• Dynamic Number Table

  - by Derek D.

  Using a numbers table is helpful for many things. Like finding gaps in a supposed sequence of primary keys, or generating date ranges or any numerical range. In some cases, you will be in a production system that does not already contain a numbers table and you will also be unable to add [...]

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• Does Hard Drive Orientation Affect Its Lifespan?

  - by Jason Fitzpatrick

  Many cases allow you to mount drives in vertical or horizontal configurations and external drives can be easily repositioned. Does the orientation of the hard drive affect the performance and longevity of the drive? Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-drive grouping of Q&A web sites. 6 Ways Windows 8 Is More Secure Than Windows 7 HTG Explains: Why It’s Good That Your Computer’s RAM Is Full 10 Awesome Improvements For Desktop Users in Windows 8

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• Determining cause of random latency and loading issues

  - by Sherwin Flight

  I'm not sure exactly what details to post in regards to my issue, because I'm not sure what is relevant. Prior to the end of September my websites all loaded quickly, in almost all cases. Loading time wasn't usually more than a few seconds. However, since the end of September I noticed a big increase in page loading times. In some cases pages were taking 30 seconds or more to load. I do have a remote monitoring service monitoring some of the sites as well, and the image below shows the response times over the past month. The response times shown at the beginning of this graph were what the usual response times were prior to this issue occurring. You can see that there has been a significant increase in response times from the beginning to the end of this graph. The thing is, the problem is not happening 100% of the time. If I click through the site, or even just keep refreshing the page, about 25% of the time the pages load quickly, the remaining 75% of the time they load slowly. Sometimes the pages take so long to load that they time out, and don't load at all. I have contacted my hosting provider, and they said things at their end was fine. I don't believe the problem is my home internet provider, because all other websites load without a problem. The server is located in Texas, USA. This also raises another interesting point. My remote monitor checks my site from two locations, California, USA, and London, England. As you can see in the chart below the response time is actually shorter when checked from London, which doesn't seem to make sense, since the server is physically closer to the California monitoring location. I would have expected the London monitoring location to have higher response times since they are physically farther away. I should also point out that in some traceroute test I've done it seem like the first connection to the server seems to take the longest, then after that the rest of the page loads quickly. Below is a little chart showing the times for the first connection to the server. So, what could be causing this problem, and what steps can I take to resolve it or at least narrow down the problem? Sending the request to the server was very quick, and receiving the reply back seems pretty quick, but the WAIT time is really long. So it connects, sends the request, but then waits close to 30 seconds before it starts receiving data back. I am also aware that there are things I can do to speed up page loading times, like reducing the number of CSS and JS files used on a page, compressing images, etc. This is not really what the source of the problem is though, because nothing has really changed on the site since before the problem started, and other sites on the same server are loading slowly as well.

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• SQLAuthority News Tips for Traveling to Nepal

  If you are a regular reader of this blog, you might know that I travel nearly 20+ days out of 30 days in a month. There are cases when I dont have a chance to go home for an entire month and my family has to travel to different cities just to meet me. During [...]...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• New White Paper about Upgrade to Oracle Database 12c

  - by Mike Dietrich

  With the release of Oracle Database 12c many new collateral will be available right now including our new White Paper: White Paper:Upgrading to Oracle Database 12c This white paper outlines the methods available for you to upgrade and migrate your database to Oracle Database 12c.  Learn about different use cases and key factors to consider when choosing the method that best fits your requirements. And if you'd like to have a look into the new Oracle 12c documentation please find it here: Oracle Database 12c Documentation -Mike

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• Simplifying C++11 optimal parameter passing when a copy is needed

  - by Mr.C64

  It seems to me that in C++11 lots of attention was made to simplify returning values from functions and methods, i.e.: with move semantics it's possible to simply return heavy-to-copy but cheap-to-move values (while in C++98/03 the general guideline was to use output parameters via non-const references or pointers), e.g.: // C++11 style vector<string> MakeAVeryBigStringList(); // C++98/03 style void MakeAVeryBigStringList(vector<string>& result); On the other side, it seems to me that more work should be done on input parameter passing, in particular when a copy of an input parameter is needed, e.g. in constructors and setters. My understanding is that the best technique in this case is to use templates and std::forward<>, e.g. (following the pattern of this answer on C++11 optimal parameter passing): class Person { std::string m_name; public: template <class T, class = typename std::enable_if < std::is_constructible<std::string, T>::value >::type> explicit Person(T&& name) : m_name(std::forward<T>(name)) { } ... }; A similar code could be written for setters. Frankly, this code seems boilerplate and complex, and doesn't scale up well when there are more parameters (e.g. if a surname attribute is added to the above class). Would it be possible to add a new feature to C++11 to simplify code like this (just like lambdas simplify C++98/03 code with functors in several cases)? I was thinking of a syntax with some special character, like @ (since introducing a &&& in addition to && would be too much typing :) e.g.: class Person { std::string m_name; public: /* Simplified syntax to produce boilerplate code like this: template <class T, class = typename std::enable_if < std::is_constructible<std::string, T>::value >::type> */ explicit Person(std::string@ name) : m_name(name) // implicit std::forward as well { } ... }; This would be very convenient also for more complex cases involving more parameters, e.g. Person(std::string@ name, std::string@ surname) : m_name(name), m_surname(surname) { } Would it be possible to add a simplified convenient syntax like this in C++? What would be the downsides of such a syntax?

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• SQL Server v.Next (Denali) : Metadata enhancements

  - by AaronBertrand

  In my previous job, we had several cases where schema changes or incorrect developer assumptions in the middle tier or application logic would lead to type mismatches. We would have a stored procedure that returns a BIT column, but then change the procedure to have something like CASE WHEN <condition> THEN 1 ELSE 0 END. In this case SQL Server would return an INT as a catch-all, and if .NET was expecting a boolean, BOOM. Wouldn't it be nice if the application could check the result set of the...(read more)

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• The battle for Internet freedom

  <b>Network World:</b> "What are we permitted to post legally on the Internet? Who is responsible for the content of materials posted on Web sites? Two recent legal cases have highlighted the ongoing battles over control of information being posted on the Internet."

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• Why many designs ignore normalization in RDBMS?

  - by Yosi

  I got to see many designs that normalization wasn't the first consideration in decision making phase. In many cases those designs included more than 30 columns, and the main approach was "to put everything in the same place" According to what I remember normalization is one of the first, most important things, so why is it dropped so easily sometimes? Edit: Is it true that good architects and experts choose a denormalized design while non-experienced developers choose the opposite? What are the arguments against starting your design with normalization in mind?

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• Game engines and monetization of indie games

  - by Extrakun

  Does the game engine you use affect monetization of indie games? Of course, targeting difficult platforms is one of the issues. Besides that, how would the game engine used impact monetization of games, assuming cases where the developers is going through a portal and handling the online distribution themselves? As an example, if I make a game in DarkBASIC, will it be harder to sell it than one made with Popcaps Framework or ClanLib etc.?

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• notify-send ignores timeout?

  - by Hooked

  Maybe I'm doing something wrong, but shouldn't the commands (run separately) notify-send -t 1 "test" notify-send -t 1000 "test" notify-send -t 10000 "test" Have different timeouts? The first being nearly instantaneous, the second one taking 1 sec and the third 100 seconds. In all cases it seems to take about six seconds. I'm using the development branch of Precise, if this isn't an issue in the released version I'll close this as being too localized, but I'm unable to test it now.

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• Denormalization Strategies

  In building a database, typically we want a well normalized design. However there are cases for considering options for denormalization in complex systems. Timothy Claason gives you some thoughts on the subject.

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• Performance Improvements: Caching

  Caching can greatly improve performance but it can also lull you into a false sense of security. In some cases it can even make the performance worse. If you haven't already, then now is the time to learn the issues and limitations of caching so that you can truly improve performance.

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• Performance Improvements: Caching

  Caching can greatly improve performance but it can also lull you into a false sense of security. In some cases it can even make the performance worse. If you haven't already, then now is the time to learn the issues and limitations of caching so that you can truly improve performance.

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• Partner Blog Series: PwC Perspectives - Looking at R2 for Customer Organizations

  - by Tanu Sood

  Welcome to the first of our partner blog series. November Mondays are all about PricewaterhouseCoopers' perespective on Identity and R2. In this series, we have identity management experts from PricewaterhouseCoopers (PwC) share their perspective on (and experiences with) the recent identity management release, Oracle Identity Management R2. The purpose of the series is to discuss real world identity use cases that helped shape the innovations in the recent R2 release and the implementation strategies that customers are employing today with expertise from PwC. Part 1: Looking at R2 for Customer Organizations In this inaugural post, we will discuss some of the new features of the R2 release of Oracle Identity Manager that some of our customer organizations are implementing today and the business rationale for those. Oracle's R2 Security portfolio represents a solid step forward for a platform that is already market-leading.  Prior to R2, Oracle was an industry titan in security with reliable products, expansive compatibility, and a large customer base.  Oracle has taken their identity platform to the next level in their latest version, R2.  The new features include a customizable UI, a request catalog, flexible security, and enhancements for its connectors, and more. Oracle customers will be impressed by the new Oracle Identity Manager (OIM) business-friendly UI.  Without question, Oracle has invested significant time in responding to customer feedback about making access requests and related activities easier for non-IT users.  The flexibility to add information to screens, hide fields that are not important to a particular customer, and adjust web themes to suit a company's preference make Oracle's Identity Manager stand out among its peers.  Customers can also expect to carry UI configurations forward with minimal migration effort to future versions of OIM.  Oracle's flexible UI will benefit many organizations looking for a customized feel with out-of-the-box configurations. Organizations looking to extend their services to end users will benefit significantly from new usability features like OIM’s ‘Catalog.’  Customers familiar with Oracle Identity Analytics' 'Glossary' feature will be able to relate to the concept.  It will enable Roles, Entitlements, Accounts, and Resources to be requested through the out-of-the-box UI.  This is an industry-changing feature as customers can make the process to request access easier than ever.  For additional ease of use, Oracle has introduced a shopping cart style request interface that further simplifies the experience for end users.  Common requests can be setup as profiles to save time.  All of this is combined with the approval workflow engine introduced in R1 that provides the flexibility customers need to meet their compliance requirements. Enhanced security was also on the list of features Oracle wanted to deliver to its customers.  The new end-user UI provides additional granular access controls.  Common Help Desk use cases can be implemented with ease by updating the application profiles.  Access can be rolled out so that administrators can only manage a certain department or organization.  Further, OIM can be more easily configured to select which fields can be read-only vs. updated.  Finally, this security model can be used to limit search results for roles and entitlements intended for a particular department.  Every customer has a different need for access and OIM now matches this need with a flexible security model. One of the important considerations when selecting an Identity Management platform is compatibility.  The number of supported platform connectors and how well it can integrate with non-supported platforms is a key consideration for selecting an identity suite.  Oracle has a long list of supported connectors.  When a customer has a requirement for a platform not on that list, Oracle has a solution too.  Oracle is introducing a simplified architecture called Identity Connector Framework (ICF), which holds the potential to simplify custom connectors.  Finally, Oracle has introduced a simplified process to profile new disconnected applications from the web browser.  This is a useful feature that enables administrators to profile applications quickly as well as empowering the application owner to fulfill requests from their web browser.  Support will still be available for connectors based on previous versions in R2. Oracle Identity Manager's new R2 version has delivered many new features customers have been asking for.  Oracle has matured their platform with R2, making it a truly distinctive platform among its peers. In our next post, expect a deep dive into use cases for a customer considering R2 as their new Enterprise identity solution. In the meantime, we look forward to hearing from you about the specific challenges you are facing and your experience in solving those. Meet the Writers Dharma Padala is a Director in the Advisory Security practice within PwC.  He has been implementing medium to large scale Identity Management solutions across multiple industries including utility, health care, entertainment, retail and financial sectors.   Dharma has 14 years of experience in delivering IT solutions out of which he has been implementing Identity Management solutions for the past 8 years. Scott MacDonald is a Director in the Advisory Security practice within PwC.  He has consulted for several clients across multiple industries including financial services, health care, automotive and retail.   Scott has 10 years of experience in delivering Identity Management solutions. John Misczak is a member of the Advisory Security practice within PwC.  He has experience implementing multiple Identity and Access Management solutions, specializing in Oracle Identity Manager and Business Process Engineering Language (BPEL). Jenny (Xiao) Zhang is a member of the Advisory Security practice within PwC.  She has consulted across multiple industries including financial services, entertainment and retail. Jenny has three years of experience in delivering IT solutions out of which she has been implementing Identity Management solutions for the past one and a half years. Praveen Krishna is a Manager in the Advisory  Security practice within PwC.  Over the last decade Praveen has helped clients plan, architect and implement Oracle identity solutions across diverse industries.  His experience includes delivering security across diverse topics like network, infrastructure, application and data where he brings a holistic point of view to problem solving.

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• Helper class to dynamically modify the Location configuration element

  - by anas

  The location element is used to restrict user or role access on a specific path.The path could be a folder,aspx page,ashx,axd or any other file that is handled by ASP.NET runtime. In most cases, you use that element declarativley in the web.config file of your website.In this case, you are declaratively telling the ASP.NET runtime and specifically the UrlAuthorizationModule or the FileAuthorizationModule (depending on the Authentication Mode) to grant/deny the access to that path for the specified...(read more)

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• Load Plan article in Oracle Magazine

  - by David Allan

  Timely article in Oracle Magazine on ODI Load Plans from Mark Rittman in the current issue, worth having a quick read of the article and play with the sample which is included if you get the time. Thanks to Mark for investing the time and energy providing such useful information to the community.http://www.oracle.com/technetwork/issue-archive/2012/12-sep/o52bi-1735905.htmlMark goes over the main benefits of the load plan in the article. Interested to hear any creative use cases or comments in general.

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