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  • Some instruction needed for PHP OOPS concepts.

    - by Avinash
    Hi, I need to clear some OOPS concepts in PHP. 1) Which is faster $this-method(); or self:method(); 2) I know the concept of static keyword but can you please post the actual Use of it. Since it can not be accessed by the instance, but is there ant benefit for that? 3) what is factory? How can i use it? 4) What is singleton? How can i use that? 5) What is late static binding? http://www.php.net/manual/en/oop5.intro.php I have gone through below link but I am not getting clear with it. Thanks Avinash

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  • Programming languages & proof of concepts

    - by Mike
    There are plenty of programming languages out there, as you all may know. I am primarily looking for a list of programming languages WITH some very neat proof of concepts. I would really like to learn a new language, but whenever I dive into something new and popular, it isn't what I expected. Any tutorial out there will give you code, small examples, but won't show you the true power of the language. I am looking for examples that run entirely on the language that it is exemplifying. For example, If I said C#, I could possibly show you a complete C# app with backend queries, reports, tables, all with a nice interface. It would be completely reliant on the language that is provided, so no supporting languages. I understand that most languages are integrated with other languages in order to provide a richer application. Any links, charts, websites that may reflect this request is appreciated.

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  • pdf to swf with deeplinking concepts

    - by Auxi
    Hi, Right now i'm working on a project which involves in converting pdf docs to swf file. Using FlexPaper (http://flexpaper.devaldi.com/), I converted pdf to swf. I have used deeplinking concepts to link to a particular page from external html link, but if I want to link to a particular bookmark/named destination, I can not be able to do so. I have tried so many ways & ended up in failure. Kindly let me know, if some one knows a way.Thanks in advance.

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  • Need some help in understanding SSL concepts

    - by user1115256
    I am new to SSL programming and finding some difficulties in understanding SSL concepts. I tried to get it through openssl site,but it is not much informative. Here is my doubts. What is difference between SSL Buffer and BIO buffer..? I mean layerwise detail will be very helpful. Can I use SSL_Write and SSL_Read without setting any BIO object to SSL object..? What exactly BIO_flush will do... I mean is it going to flush all the data to network buffer from BIO buffer.. ? If it is possible to do write and read data from SSL directly without using any BIO object then is it possible to flush the data from SSL buffer to network buffer by any means.. ? It would be very helpful if any body explain these things or giving any links where I can find answers to my questions.

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  • Error Handling Examples(C#)

    “The purpose of reviewing the Error Handling code is to assure that the application fails safely under all possible error conditions, expected and unexpected. No sensitive information is presented to the user when an error occurs.” (OWASP, 2011) No Error Handling The absence of error handling is still a form of error handling. Based on the code in Figure 1, if an error occurred and was not handled within either the ReadXml or BuildRequest methods the error would bubble up to the Search method. Since this method does not handle any acceptations the error will then bubble up the stack trace. If this continues and the error is not handled within the application then the environment in which the application is running will notify the user running the application that an error occurred based on what type of application. Figure 1: No Error Handling public DataSet Search(string searchTerm, int resultCount) { DataSet dt = new DataSet(); dt.ReadXml(BuildRequest(searchTerm, resultCount)); return dt; } Generic Error Handling One simple way to add error handling is to catch all errors by default. If you examine the code in Figure 2, you will see a try-catch block. On April 6th 2010 Louis Lazaris clearly describes a Try Catch statement by defining both the Try and Catch aspects of the statement. “The try portion is where you would put any code that might throw an error. In other words, all significant code should go in the try section. The catch section will also hold code, but that section is not vital to the running of the application. So, if you removed the try-catch statement altogether, the section of code inside the try part would still be the same, but all the code inside the catch would be removed.” (Lazaris, 2010) He also states that all errors that occur in the try section cause it to stops the execution of the try section and redirects all execution to the catch section. The catch section receives an object containing information about the error that occurred so that they system can gracefully handle the error properly. When errors occur they commonly log them in some form. This form could be an email, database entry, web service call, log file, or just an error massage displayed to the user.  Depending on the error sometimes applications can recover, while others force an application to close. Figure 2: Generic Error Handling public DataSet Search(string searchTerm, int resultCount) { DataSet dt = new DataSet(); try { dt.ReadXml(BuildRequest(searchTerm, resultCount)); } catch (Exception ex) { // Handle all Exceptions } return dt; } Error Specific Error Handling Like the Generic Error Handling, Error Specific error handling allows for the catching of specific known errors that may occur. For example wrapping a try catch statement around a soap web service call would allow the application to handle any error that was generated by the soap web service. Now, if the systems wanted to send a message to the web service provider every time a soap error occurred but did not want to notify them if any other type of error occurred like a network time out issue. This would be varying tedious to accomplish using the General Error Handling methodology. This brings us to the use case for using the Error Specific error handling methodology.  The Error Specific Error handling methodology allows for the TryCatch statement to catch various types of errors depending on the type of error that occurred. In Figure 3, the code attempts to handle DataException differently compared to how it potentially handles all other errors. This allows for specific error handling for each type of known error, and still allows for error handling of any unknown error that my occur during the execution of the TryCatch statement. Figure 5: Error Specific Error Handling public DataSet Search(string searchTerm, int resultCount) { DataSet dt = new DataSet(); try { dt.ReadXml(BuildRequest(searchTerm, resultCount)); } catch (TimeoutException ex) { // Handle Timeout TimeoutException Only } catch (Exception) { // Handle all Exceptions } return dt; }

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  • Windows Azure Use Case: Hybrid Applications

    - by BuckWoody
    This is one in a series of posts on when and where to use a distributed architecture design in your organization's computing needs. You can find the main post here: http://blogs.msdn.com/b/buckwoody/archive/2011/01/18/windows-azure-and-sql-azure-use-cases.aspx  Description: Organizations see the need for computing infrastructures that they can “rent” or pay for only when they need them. They also understand the benefits of distributed computing, but do not want to create this infrastructure themselves. However, they may have considerations that prevent them from moving all of their current IT investment to a distributed environment: Private data (do not want to send or store sensitive data off-site) High dollar investment in current infrastructure Applications currently running well, but may need additional periodic capacity Current applications not designed in a stateless fashion In these situations, a “hybrid” approach works best. In fact, with Windows Azure, a hybrid approach is an optimal way to implement distributed computing even when the stipulations above do not apply. Keeping a majority of the computing function in an organization local while exploring and expanding that footprint into Windows and SQL Azure is a good migration or expansion strategy. A “hybrid” architecture merely means that part of a computing cycle is shared between two architectures. For instance, some level of computing might be done in a Windows Azure web-based application, while the data is stored locally at the organization. Implementation: There are multiple methods for implementing a hybrid architecture, in a spectrum from very little interaction from the local infrastructure to Windows or SQL Azure. The patterns fall into two broad schemas, and even these can be mixed. 1. Client-Centric Hybrid Patterns In this pattern, programs are coded such that the client system sends queries or compute requests to multiple systems. The “client” in this case might be a web-based codeset actually stored on another system (which acts as a client, the user’s device serving as the presentation layer) or a compiled program. In either case, the code on the client requestor carries the burden of defining the layout of the requests. While this pattern is often the easiest to code, it’s the most brittle. Any change in the architecture must be reflected on each client, but this can be mitigated by using a centralized system as the client such as in the web scenario. 2. System-Centric Hybrid Patterns Another approach is to create a distributed architecture by turning on-site systems into “services” that can be called from Windows Azure using the service Bus or the Access Control Services (ACS) capabilities. Code calls from a series of in-process client application. In this pattern you move the “client” interface into the server application logic. If you do not wish to change the application itself, you can “layer” the results of the code return using a product (such as Microsoft BizTalk) that exposes a Web Services Definition Language (WSDL) endpoint to Windows Azure using the Application Fabric. In effect, this is similar to creating a Service Oriented Architecture (SOA) environment, and has the advantage of de-coupling your computing architecture. If each system offers a “service” of the results of some software processing, the operating system or platform becomes immaterial, assuming it adheres to a service contract. There are important considerations when you federate a system, whether to Windows or SQL Azure or any other distributed architecture. While these considerations are consistent with coding any application for distributed computing, they are especially important for a hybrid application. Connection resiliency - Applications on-premise normally have low-latency and good connection properties, something you’re not always guaranteed in a distributed and hybrid application. Whether a centralized client or a distributed one, the code should be able to handle extended retry logic. Authorization and Access - In a single authorization environment like a Active Directory domain, security is handled at a user-password level. In a distributed computing environment, you have more options. You can mitigate this with  using The Windows Azure Application Fabric feature of ACS to make the Azure application aware of the App Fabric as an ADFS provider. However, a claims-based authentication structure is often a superior choice.  Consistency and Concurrency - When you have a Relational Database Management System (RDBMS), Consistency and Concurrency are part of the design. In a Service Architecture, you need to plan for sequential message handling and lifecycle. Resources: How to Build a Hybrid On-Premise/In Cloud Application: http://blogs.msdn.com/b/ignitionshowcase/archive/2010/11/09/how-to-build-a-hybrid-on-premise-in-cloud-application.aspx  General Architecture guidance: http://blogs.msdn.com/b/buckwoody/archive/2010/12/21/windows-azure-learning-plan-architecture.aspx   

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  • Windows Azure Use Case: Web Applications

    - by BuckWoody
    This is one in a series of posts on when and where to use a distributed architecture design in your organization's computing needs. You can find the main post here: http://blogs.msdn.com/b/buckwoody/archive/2011/01/18/windows-azure-and-sql-azure-use-cases.aspx  Description: Many applications have a requirement to be located outside of the organization’s internal infrastructure control. For instance, the company website for a brick-and-mortar retail company may want to post not only static but interactive content to be available to their external customers, and not want the customers to have access inside the organization’s firewall. There are also cases of pure web applications used for a great many of the internal functions of the business. This allows for remote workers, shared customer/employee workloads and data and other advantages. Some firms choose to host these web servers internally, others choose to contract out the infrastructure to an “ASP” (Application Service Provider) or an Infrastructure as a Service (IaaS) company. In any case, the design of these applications often resembles the following: In this design, a server (or perhaps more than one) hosts the presentation function (http or https) access to the application, and this same system may hold the computational aspects of the program. Authorization and Access is controlled programmatically, or is more open if this is a customer-facing application. Storage is either placed on the same or other servers, hosted within an RDBMS or NoSQL database, or a combination of the options, all coded into the application. High-Availability within this scenario is often the responsibility of the architects of the application, and by purchasing more hosting resources which must be built, licensed and configured, and manually added as demand requires, although some IaaS providers have a partially automatic method to add nodes for scale-out, if the architecture of the application supports it. Disaster Recovery is the responsibility of the system architect as well. Implementation: In a Windows Azure Platform as a Service (PaaS) environment, many of these architectural considerations are designed into the system. The Azure “Fabric” (not to be confused with the Azure implementation of Application Fabric - more on that in a moment) is designed to provide scalability. Compute resources can be added and removed programmatically based on any number of factors. Balancers at the request-level of the Fabric automatically route http and https requests. The fabric also provides High-Availability for storage and other components. Disaster recovery is a shared responsibility between the facilities (which have the ability to restore in case of catastrophic failure) and your code, which should build in recovery. In a Windows Azure-based web application, you have the ability to separate out the various functions and components. Presentation can be coded for multiple platforms like smart phones, tablets and PC’s, while the computation can be a single entity shared between them. This makes the applications more resilient and more object-oriented, and lends itself to a SOA or Distributed Computing architecture. It is true that you could code up a similar set of functionality in a traditional web-farm, but the difference here is that the components are built into the very design of the architecture. The API’s and DLL’s you call in a Windows Azure code base contains components as first-class citizens. For instance, if you need storage, it is simply called within the application as an object.  Computation has multiple options and the ability to scale linearly. You also gain another component that you would either have to write or bolt-in to a typical web-farm: the Application Fabric. This Windows Azure component provides communication between applications or even to on-premise systems. It provides authorization in either person-based or claims-based perspectives. SQL Azure provides relational storage as another option, and can also be used or accessed from on-premise systems. It should be noted that you can use all or some of these components individually. Resources: Design Strategies for Scalable Active Server Applications - http://msdn.microsoft.com/en-us/library/ms972349.aspx  Physical Tiers and Deployment  - http://msdn.microsoft.com/en-us/library/ee658120.aspx

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  • The Windows Azure Software Development Kit (SDK) and the Windows Azure Training Kit (WATK)

    - by BuckWoody
    Windows Azure is a platform that allows you to write software, run software, or use software that we've already written. We provide lots of resources to help you do that - many can be found right here in this blog series. There are two primary resources you can use, and it's important to understand what they are and what they do. The Windows Azure Software Development Kit (SDK) Actually, this isn't one resource. We have SDK's for multiple development environments, such as Visual Studio and also Eclipse, along with SDK's for iOS, Android and other environments. Windows Azure is a "back end", so almost any technology or front end system can use it to solve a problem. The SDK's are primarily for development. In the case of Visual Studio, you'll get a runtime environment for Windows Azure which allows you to develop, test and even run code all locally - you do not have to be connected to Windows Azure at all, until you're ready to deploy. You'll also get a few samples and codeblocks, along with all of the libraries you need to code with Windows Azure in .NET, PHP, Ruby, Java and more. The SDK is updated frequently, so check this location to find the latest for your environment and language - just click the bar that corresponds to what you want: http://www.windowsazure.com/en-us/develop/downloads/ The Windows Azure Training Kit (WATK) Whether you're writing code, using Windows Azure Virtual Machines (VM's) or working with Hadoop, you can use the WATK to get examples, code, PowerShell scripts, PowerPoint decks, training videos and much more. This should be your second download after the SDK. This is all of the training you need to get started, and even beyond. The WATK is updated frequently - and you can find the latest one here: http://www.windowsazure.com/en-us/develop/net/other-resources/training-kit/     There are many other resources - again, check the http://windowsazure.com site, the community newsletter (which introduces the latest features), and my blog for more.

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  • Modular programming is the method of programming small task or programs

    Modular programming is the method of programming small task or sub-programs that can be arranged in multiple variations to perform desired results. This methodology is great for preventing errors due to the fact that each task executes a specific process and can be debugged individually or within a larger program when combined with other tasks or sub programs. C# is a great example of how to implement modular programming because it allows for functions, methods, classes and objects to be use to create smaller sub programs. A program can be built from smaller pieces of code which saves development time and reduces the chance of errors because it is easier to test a small class or function for a simple solutions compared to testing a full program which has layers and layers of small programs working together.Yes, it is possible to write the same program using modular and non modular programming, but it is not recommend it. When you deal with non modular programs, they tend to contain a lot of spaghetti code which can be a pain to develop and not to mention debug especially if you did not write the code. In addition, in my experience they seem to have a lot more hidden bugs which waste debugging and development time. Modular programming methodology in comparision to non-mondular should be used when ever possible due to the use of small components. These small components allow business logic to be reused and is easier to maintain. From the user’s view point, they cannot really tell if the code is modular or not with today’s computers.

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  • The Data Scientist

    - by BuckWoody
    A new term - well, perhaps not that new - has come up and I’m actually very excited about it. The term is Data Scientist, and since it’s new, it’s fairly undefined. I’ll explain what I think it means, and why I’m excited about it. In general, I’ve found the term deals at its most basic with analyzing data. Of course, we all do that, and the term itself in that definition is redundant. There is no science that I know of that does not work with analyzing lots of data. But the term seems to refer to more than the common practices of looking at data visually, putting it in a spreadsheet or report, or even using simple coding to examine data sets. The term Data Scientist (as far as I can make out this early in it’s use) is someone who has a strong understanding of data sources, relevance (statistical and otherwise) and processing methods as well as front-end displays of large sets of complicated data. Some - but not all - Business Intelligence professionals have these skills. In other cases, senior developers, database architects or others fill these needs, but in my experience, many lack the strong mathematical skills needed to make these choices properly. I’ve divided the knowledge base for someone that would wear this title into three large segments. It remains to be seen if a given Data Scientist would be responsible for knowing all these areas or would specialize. There are pretty high requirements on the math side, specifically in graduate-degree level statistics, but in my experience a company will only have a few of these folks, so they are expected to know quite a bit in each of these areas. Persistence The first area is finding, cleaning and storing the data. In some cases, no cleaning is done prior to storage - it’s just identified and the cleansing is done in a later step. This area is where the professional would be able to tell if a particular data set should be stored in a Relational Database Management System (RDBMS), across a set of key/value pair storage (NoSQL) or in a file system like HDFS (part of the Hadoop landscape) or other methods. Or do you examine the stream of data without storing it in another system at all? This is an important decision - it’s a foundation choice that deals not only with a lot of expense of purchasing systems or even using Cloud Computing (PaaS, SaaS or IaaS) to source it, but also the skillsets and other resources needed to care and feed the system for a long time. The Data Scientist sets something into motion that will probably outlast his or her career at a company or organization. Often these choices are made by senior developers, database administrators or architects in a company. But sometimes each of these has a certain bias towards making a decision one way or another. The Data Scientist would examine these choices in light of the data itself, starting perhaps even before the business requirements are created. The business may not even be aware of all the strategic and tactical data sources that they have access to. Processing Once the decision is made to store the data, the next set of decisions are based around how to process the data. An RDBMS scales well to a certain level, and provides a high degree of ACID compliance as well as offering a well-known set-based language to work with this data. In other cases, scale should be spread among multiple nodes (as in the case of Hadoop landscapes or NoSQL offerings) or even across a Cloud provider like Windows Azure Table Storage. In fact, in many cases - most of the ones I’m dealing with lately - the data should be split among multiple types of processing environments. This is a newer idea. Many data professionals simply pick a methodology (RDBMS with Star Schemas, NoSQL, etc.) and put all data there, regardless of its shape, processing needs and so on. A Data Scientist is familiar not only with the various processing methods, but how they work, so that they can choose the right one for a given need. This is a huge time commitment, hence the need for a dedicated title like this one. Presentation This is where the need for a Data Scientist is most often already being filled, sometimes with more or less success. The latest Business Intelligence systems are quite good at allowing you to create amazing graphics - but it’s the data behind the graphics that are the most important component of truly effective displays. This is where the mathematics requirement of the Data Scientist title is the most unforgiving. In fact, someone without a good foundation in statistics is not a good candidate for creating reports. Even a basic level of statistics can be dangerous. Anyone who works in analyzing data will tell you that there are multiple errors possible when data just seems right - and basic statistics bears out that you’re on the right track - that are only solvable when you understanding why the statistical formula works the way it does. And there are lots of ways of presenting data. Sometimes all you need is a “yes” or “no” answer that can only come after heavy analysis work. In that case, a simple e-mail might be all the reporting you need. In others, complex relationships and multiple components require a deep understanding of the various graphical methods of presenting data. Knowing which kind of chart, color, graphic or shape conveys a particular datum best is essential knowledge for the Data Scientist. Why I’m excited I love this area of study. I like math, stats, and computing technologies, but it goes beyond that. I love what data can do - how it can help an organization. I’ve been fortunate enough in my professional career these past two decades to work with lots of folks who perform this role at companies from aerospace to medical firms, from manufacturing to retail. Interestingly, the size of the company really isn’t germane here. I worked with one very small bio-tech (cryogenics) company that worked deeply with analysis of complex interrelated data. So  watch this space. No, I’m not leaving Azure or distributed computing or Microsoft. In fact, I think I’m perfectly situated to investigate this role further. We have a huge set of tools, from RDBMS to Hadoop to allow me to explore. And I’m happy to share what I learn along the way.

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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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  • How to protect a peer-to-peer network from inappropriate content?

    - by Mike
    I’m developing a simple peer-to-peer app in .Net which should enable users to share specific content (text and picture files). As I've learned with my last question, inappropriate content can “relatively” easily be identified / controlled in a centralized environment. But what about a peer-to-peer network, what are the best methods to protect a decentralized system from unwanted (illegal) content? At the moment I only see the following two methods: A protocol (a set of rules) defines what kind of data (e.g. only .txt and jpg-files, not bigger than 20KB etc.) can be shared over the p2p-network and all clients (peers) must implement this protocol. If a peer doesn’t, it gets blocked by other peers. Pro: easy to implement. Con: It’s not possible to define the perfect protocol (I think eMail-Spam filters have the same problem) Some kind of rating/reputation system must be implemented (similar to stackoverflow), so “bad guys” and inappropriate content can be identified / blocked by other users. Pro: Would be very accurate. Con: Would be slow and in my view technically very hard to implement. Are there other/better solutions? Any answer or comment is highly appreciated.

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  • Collocation in Code

    - by Dan McGrath
    Quite some time ago I remember reading an article from 'Joel on Software' that mentioned collocation of information in code was important. By collocation, I mean that relevant information about the code is present when the code is. I'm currently writing an article that has a small bit in it about collocation so I went searching for sources and found the quote in the article 'Making Wrong Code Look Wrong' In order to make code really, really robust, when you code-review it, you need to have coding conventions that allow collocation. In other words, the more information about what code is doing is located right in front of your eyes, the better a job you’ll do at finding the mistakes. When you have code that says For me, collocation isn't just about the code itself, but the tool used to view the code. If it can help with the 'collocation factor' (term coined by me?) I believe it can help with the programmers productivity. Take for example the modern IDEs that show you the variables type by hovering over it. Are their any other articles written about collocation in code and/or are their other terms that this is known by?

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  • Programming knowledge vs. programming logic

    - by Shirish11
    Is there any difference between the two topics? I have seen companies asking for Good Programming knowledge some Good Programming logic. I believe that Programming knowledge is related to knowledge about the language in consideration and Programming logic is problem solving logic using programming (in general). Please correct me if I am wrong. Also what is more important. Edit: Do selection of components for application, designing interfaces validating user inputs fall under programming knowledge or Programming logic? Does programming logic simply imply problem solving, or is there anything else which it should comprise of?

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  • Books or help on OO Analysis

    - by Pat
    I have this course where we learn about the domain model, use cases, contracts and eventually leap into class diagrams and sequence diagrams to define good software classes. I just had an exam and I got trashed, but part of the reason is we barely have any practical material, I spent at least two good months without drawing a single class diagram by myself from a case study. I'm not here to blame the system or the class I'm in, I'm just wondering if people have some exercise-style books that either provide domain models with glossaries, system sequence diagrams and ask you to use GRASP to make software classes? I could really use some alone-time practicing going from analysis to conception of software entities. I'm almost done with Larman's book called "Applying UML and Patterns An Introduction to Object-Oriented Analysis and Design and Iterative Development, Third Edition". It's a good book, but I'm not doing anything by myself since it doesn't come with exercises. Thanks.

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  • what is need for a handler in general

    - by nish
    I have been searching for a definition for handler. basics i've understood that "A handler is a piece of code that is called when something happens, and usually takes some action, like generating a response." - (from http://stackoverflow.com/questions/3246200/what-is-an-handler ). But that can be a trigger or a callback. Also in specific an event handler on a low-level , often works by polling a device and waiting for a hardware response. So, what is the specific role of a handler ( that makes it unique from a trigger or a callback or any other such function ). Do all handlers have similar role ( event handler, file handler , exception handler, error handler )...

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  • Map Library: Client-side or Server-side?

    - by Mahdi
    As I have already asked here, I have to implement a Multi-Platform Map application. Now I have Mapstraction as an option which uses Javascript to implement the desired functionality. My question is, "Is there any reason/benefit to implement such a library (let say, Adapters) in Server-side (in my case, PHP)?" As these maps are all based on Javascript, there is a big reason to use Javascript again to make the adapter also, so it would not be dependent to PHP, Java, or .NET for example. But is that all? I wish to hear your ideas and comments also. :)

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  • You Probably Already Have a “Private Cloud”

    - by BuckWoody
    I’ve mentioned before that I’m not a fan of the word “Cloud”. It’s too marketing-oriented, gimmicky and non-specific. A better definition (in many cases) is “Distributed Computing”. That means that some or all of the computing functions are handled somewhere other than under your specific control. But there is a current use of the word “Cloud” that does not necessarily mean that the computing is done somewhere else. In fact, it’s a vector of Cloud Computing that can better be termed “Utility Computing”. This has to do with the provisioning of a computing resource. That means the setup, configuration, management, balancing and so on that is needed so that a user – which might actually be a developer – can do some computing work. To that person, the resource is just “there” and works like they expect, like the phone system or any other utility. The interesting thing is, you can do this yourself. In fact, you probably already have been, or are now. It’s got a cool new trendy term – “Private Cloud”, but the fact is, if you have your setup automated, the HA and DR handled, balancing and performance tuning done, and a process wrapped around it all, you can call yourself a “Cloud Provider”. A good example here is your E-Mail system. your users – pretty much your whole company – just logs into e-mail and expects it to work. To them, you are the “Cloud” provider. On your side, the more you automate and provision the system, the more you act like a Cloud Provider. Another example is a database server. In this case, the “end user” is usually the development team, or perhaps your SharePoint group and so on. The data professionals configure, monitor, tune and balance the system all the time. The more this is automated, the more you’re acting like a Cloud Provider. Lots of companies help you do this in your own data centers, from VMWare to IBM and many others. Microsoft's offering in this is based around System Center – they have a “cloud in a box” provisioning system that’s actually pretty slick. The most difficult part of operating a Private Cloud is probably the scale factor. In the case of Windows and SQL Azure, we handle this in multiple ways – and we're happy to share how we do it. It’s not magic, and the algorithms for balancing (like the one we started with called Paxos) are well known. The key is the knowledge, infrastructure and people. Sure, you can do this yourself, and in many cases such as top-secret or private systems, you probably should. But there are times where you should evaluate using Azure or other vendors, or even multiple vendors to spread your risk. All of this should be based on client need, not on what you know how to do already. So congrats on your new role as a “Cloud Provider”. If you have an E-mail system or a database platform, you can just put that right on your resume.

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  • Breaking The Promise of Web Service Interoperability

    The promise of web service interoperability is achievable if certain technical and non-technical issues are dealt with properly. As the world gets smaller and smaller thanks to our growing global economy the need for security is increasing. The use of security is vital in the transferring of data from one server to another. As new security standards and protocols are created, the environments for web service hosts and clients must be in sync so that they can communicate on the same standard and protocols. For example, if a new protocol x can only be implemented on computers built after 2010 then all computers built prior to 2010 will not be able to connect to any web service hosts that only use this protocol in its security policy. If both the host and client of a web service cannot communicate using a set of common standards and protocols then web services are not available to these clients thus breaking the promise of interoperability. Another limiting factor of web services is governmental policies and regulations. I have experienced this first hand last year when I had to work on a project that dealt with personally identifiable information (PII) regarding US and Canadian Citizens. Currently the Canadian government regulates that any data pertaining to Canadian citizens must be store in Canada only. The issue that we had was that fact that we are a US based company that sometimes works with Canadian PII as part of a service that we provide. As you can see we are US based company and dealing with Canadian Data, so we had to place a file server inside the border of Canada in order for us to continue working for our Canadian customers.

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  • First Experience with Web Services

    When I first started programming with Microsoft .Net (1.0 Framework) I had a strong desire to learn how search engines indexed web sites. At that time I was a working as a search engine spammer creating web pages to generate traffic for specific themes for various clients. One way I attempted to better understand .Net was to build a web spider that analyzed web pages on demand. An example of the spider is hosted at AddLinkz.com. After my spider was built I had no real idea what I could/should do with it until I found the MSN Search API. I used this web service to compare its results with my spider. Additionally, I used the API to feed my .Net web spider new URLs from the API based on specific search terms. MSN’s search API was very easy to use, I just had to request information by calling a web URL with parameters via a Get request and the results were returned in XML. At that time all requests were limited to XML responses and a maximum of 1,000 results per query.   Since then the entire API has gone through several reconstructions, rebranding and new search services.  Microsoft’s new Bing API replaced the older MSN search API and added several new search capabilities. These new features allow search data to be returned for web searches, image searches, new searches, and related search terms to name a few. Bing API Version 2.0 SourceTypes Web Searches for web content Sushi Image Searches for images on the web Sushi News Searches news stories Sushi InstantAnswer Searches Encarta online what is sushi, convert 5 feet to meters, x*5=7, and 2 plus 2 Spell Searches Encarta dictionary for spelling suggestions Phonebook Searches phonebook entries sushi in Los Angeles RelatedSearch Returns the query strings most similar to yours Ad Returns advertisements to incorporate with results I currently plan to start using the web search feature from the new Bing 2.0 API in an open source project related to exception management. Currently, it is still in the conception phase.

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  • Why do I need two Instances in Windows Azure?

    - by BuckWoody
    Windows Azure as a Platform as a Service (PaaS) means that there are various components you can use in it to solve a problem: Compute “Roles” - Computers running an OS and optionally IIS - you can have more than one "Instance" of a given Role Storage - Blobs, Tables and Queues for Storage Other Services - Things like the Service Bus, Azure Connection Services, SQL Azure and Caching It’s important to understand that some of these services are Stateless and others maintain State. Stateless means (at least in this case) that a system might disappear from one physical location and appear elsewhere. You can think of this as a cashier at the front of a store. If you’re in line, a cashier might take his break, and another person might replace him. As long as the order proceeds, you as the customer aren’t really affected except for the few seconds it takes to change them out. The cashier function in this example is stateless. The Compute Role Instances in Windows Azure are Stateless. To upgrade hardware, because of a fault or many other reasons, a Compute Role's Instance might stop on one physical server, and another will pick it up. This is done through the controlling fabric that Windows Azure uses to manage the systems. It’s important to note that storage in Azure does maintain State. Your data will not simply disappear - it is maintained - in fact, it’s maintained three times in a single datacenter and all those copies are replicated to another for safety. Going back to our example, storage is similar to the cash register itself. Even though a cashier leaves, the record of your payment is maintained. So if a Compute Role Instance can disappear and re-appear, the things running on that first Instance would stop working. If you wrote your code in a Stateless way, then another Role Instance simply re-starts that transaction and keeps working, just like the other cashier in the example. But if you only have one Instance of a Role, then when the Role Instance is re-started, or when you need to upgrade your own code, you can face downtime, since there’s only one. That means you should deploy at least two of each Role Instance not only for scale to handle load, but so that the first “cashier” has someone to replace them when they disappear. It’s not just a good idea - to gain the Service Level Agreement (SLA) for our uptime in Azure it’s a requirement. We point this out right in the Management Portal when you deploy the application: (Click to enlarge) When you deploy a Role Instance you can also set the “Upgrade Domain”. Placing Roles on separate Upgrade Domains means that you have a continuous service whenever you upgrade (more on upgrades in another post) - the process looks like this for two Roles. This example covers the scenario for upgrade, so you have four roles total - One Web and one Worker running the "older" code, and one of each running the new code. In all those Roles you want at least two instances, and this example shows that you're covered for High Availability and upgrade paths: The take-away is this - always plan for forward-facing Roles to have at least two copies. For Worker Roles that do background processing, there are ways to architect around this number, but it does affect the SLA if you have only one.

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  • 'dock' working in simple words

    - by Shirish11
    I would like to know the idea behind the working of 'docking' in applications. I have worked with applications where components from individual forms are docked on a single main form to provide the necessary GUI. But I don't have any idea whats happening in the background. According to Wikipedia A dock is a graphical user interface element that typically provides the user with a way of launching, switching between, and monitoring running programs or applications. Now I am a bit confused if it is some component or an event or a property or something else. EDIT : The applications was developed in Delphi on windows platform. There is something more in Delphi (manual dock and automatic dock).

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  • Software development, basics of design, conventions and scalability

    - by goce ribeski
    I need to improve my programming skills in order to achieve better scalability for the software I'm working on. Purpose is to learn the rules of adding new modules and features, so when it comes to maintaining existing ones there is some concept. So, I'm looking for a good book, tutorial or websites where I can continue to read about this. Currently, what I know and what I do is: to design relational database(3NF), make separate class for each table put that in MVC implement modular programming ...write code and hope for the best... I presume that next things I need to learn more deeply are: programming codex(naming, commenting, conventions...), organize functions building interfaces organizing custom made libraries, organizing API that I'm using, documenting, team work... ... At last what my job is, it does't need to affect your answer, PHP CodeIgniter developer.

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  • High Availability for IaaS, PaaS and SaaS in the Cloud

    - by BuckWoody
    Outages, natural disasters and unforeseen events have proved that even in a distributed architecture, you need to plan for High Availability (HA). In this entry I'll explain a few considerations for HA within Infrastructure-as-a-Service (IaaS), Platform-as-a-Service (PaaS) and Software-as-a-Service (SaaS). In a separate post I'll talk more about Disaster Recovery (DR), since each paradigm has a different way to handle that. Planning for HA in IaaS IaaS involves Virtual Machines - so in effect, an HA strategy here takes on many of the same characteristics as it would on-premises. The primary difference is that the vendor controls the hardware, so you need to verify what they do for things like local redundancy and so on from the hardware perspective. As far as what you can control and plan for, the primary factors fall into three areas: multiple instances, geographical dispersion and task-switching. In almost every cloud vendor I've studied, to ensure your application will be protected by any level of HA, you need to have at least two of the Instances (VM's) running. This makes sense, but you might assume that the vendor just takes care of that for you - they don't. If a single VM goes down (for whatever reason) then the access to it is lost. Depending on multiple factors, you might be able to recover the data, but you should assume that you can't. You should keep a sync to another location (perhaps the vendor's storage system in another geographic datacenter or to a local location) to ensure you can continue to serve your clients. You'll also need to host the same VM's in another geographical location. Everything from a vendor outage to a network path problem could prevent your users from reaching the system, so you need to have multiple locations to handle this. This means that you'll have to figure out how to manage state between the geo's. If the system goes down in the middle of a transaction, you need to figure out what part of the process the system was in, and then re-create or transfer that state to the second set of systems. If you didn't write the software yourself, this is non-trivial. You'll also need a manual or automatic process to detect the failure and re-route the traffic to your secondary location. You could flip a DNS entry (if your application can tolerate that) or invoke another process to alias the first system to the second, such as load-balancing and so on. There are many options, but all of them involve coding the state into the application layer. If you've simply moved a state-ful application to VM's, you may not be able to easily implement an HA solution. Planning for HA in PaaS Implementing HA in PaaS is a bit simpler, since it's built on the concept of stateless applications deployment. Once again, you need at least two copies of each element in the solution (web roles, worker roles, etc.) to remain available in a single datacenter. Also, you need to deploy the application again in a separate geo, but the advantage here is that you could work out a "shared storage" model such that state is auto-balanced across the world. In fact, you don't have to maintain a "DR" site, the alternate location can be live and serving clients, and only take on extra load if the other site is not available. In Windows Azure, you can use the Traffic Manager service top route the requests as a type of auto balancer. Even with these benefits, I recommend a second backup of storage in another geographic location. Storage is inexpensive; and that second copy can be used for not only HA but DR. Planning for HA in SaaS In Software-as-a-Service (such as Office 365, or Hadoop in Windows Azure) You have far less control over the HA solution, although you still maintain the responsibility to ensure you have it. Since each SaaS is different, check with the vendor on the solution for HA - and make sure you understand what they do and what you are responsible for. They may have no HA for that solution, or pin it to a particular geo, or perhaps they have a massive HA built in with automatic load balancing (which is often the case).   All of these options (with the exception of SaaS) involve higher costs for the design. Do not sacrifice reliability for cost - that will always cost you more in the end. Build in the redundancy and HA at the very outset of the project - if you try to tack it on later in the process the business will push back and potentially not implement HA. References: http://www.bing.com/search?q=windows+azure+High+Availability  (each type of implementation is different, so I'm routing you to a search on the topic - look for the "Patterns and Practices" results for the area in Azure you're interested in)

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  • What programming concept is used in Nokia Lumina City Lens application [closed]

    - by gowri
    I am totally impressed about the Nokia City Lens application. How does the Nokia Lumia City Lens app work? Nokia Lumia City Lens app detects shops, restaurants, etc. by scanning the visual environment. But how can it detect shops or anything by only scanning visual information? Because we need a 360 degree view to detect a location. Because we can't simply match visual information and get that data. The visuals will change proportionally with distance and angle. So how does this app match the location and retrieve the information? Can anyone explain the concept What technology or algorithm is used in this app?

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