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  • What are the relative merits for implementing an Erlang-style "Continuation" pattern in C#

    - by JoeGeeky
    What are the relative merits (or demerits) for implementing an Erlang-style "Continuation" pattern in C#. I'm working on a project that has a large number of Lowest priority threads and I'm wondering if my approach may be all wrong. It would seem there is a reasonable upper limit to the number of long-running threads that any one Process 'should' spawn. With that said, I'm not sure what would signal the tipping-point for too many thread or when alternate patterns such as "Continuation" would be more suitable. In this case, many of the threads do a small amount of work and then sleep until woken to go again (Ex. Heartbeat, purge caches, etc...). This continues for the life of the Process.

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  • Use adapter pattern for coupled classes

    - by kaiseroskilo
    I need (for unit testing purposes) to create adapters for external library classes.ExchangeService and ContactsFolder are Microsoft's implementations in its' EWS library. So I created my adapters that implement my interfaces, but it seems that contactsFolder has a dependency for ExchangeService in its' constructor. The problem is that I cannot instantiate ContactsFolderAdapter without somehow accessing the actual ExchangeService instance (I see only ExchangeServiceAdapter in scope). Is there a better pattern for this that retains the adapter classes? Or should I "infect" ExchangeServiceAdapter with some kind of GetActualObject method?

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  • design pattern for unit testing? [duplicate]

    - by Maddy.Shik
    This question already has an answer here: Unit testing best practices for a unit testing newbie 4 answers I am beginner in developing test cases, and want to follow good patterns for developing test cases rather than following some person or company's specific ideas. Some people don't make test cases and just develop the way their senior have done in their projects. I am facing lot problems like object dependencies (when want to test method which persist A object i have to first persist B object since A is child of B). Please suggest some good books or sites preferably for learning design pattern for unit test cases. Or reference to some good source code or some discussion for Dos and Donts will do wonder. So that i can avoid doing mistakes be learning from experience of others.

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  • design pattern for unit testing?

    - by Maddy.Shik
    I am beginner in developing test cases, and want to follow good patterns for developing test cases rather than following some person or company's specific ideas. Some people don't make test cases and just develop the way their senior have done in their projects. I am facing lot problems like object dependencies (when want to test method which persist A object i have to first persist B object since A is child of B). Please suggest some good books or sites preferably for learning design pattern for unit test cases. Or reference to some good source code or some discussion for Dos and Donts will do wonder. So that i can avoid doing mistakes be learning from experience of others.

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  • How to solve cyclic dependencies in a visitor pattern

    - by Benjamin Rogge
    When programming at work we now and then face a problem with visitors and module/project dependencies. Say you have a class A in a module X. And there are subclasses B and C in module Y. That means that module Y is dependent on module X. If we want to implement a visitor pattern to the class hierarchy, thus introducing an interface with the handle Operations and an abstract accept method in A, we get a dependency from module Y to module X, which we cannot allow for architectural reasons. What we do is, use a direct comparison of the types (i.e. instanceof, since we program in Java), which is not satisfying. My question(s) would be: Do you encounter this kind of problem in your daily work (or do we make poor architectural choices) and if so, how is your approach to solve this?

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  • does class reference itself static anti pattern in prism

    - by Michael Riva
    I have an application and my desing approach look like this: class Manager { public int State; static Manager _instance = null; public static Manager Instance { get { return _instance; } set { if (_instance == value) return; _instance = value; } } public Manager() { State = 0; Instance=this; } } class Module1 { public void GetState() { Console.WriteLine(Manager.Instance.State); } } class Module2 { public void GetState() { Console.WriteLine(Manager.Instance.State); } } class Module3 { public void GetState() { Console.WriteLine(Manager.Instance.State); } } Manager class already registered in Bootstrapper like : protected override void ConfigureContainer() { base.ConfigureContainer(); Container.RegisterType<Manager>(new ContainerControlledLifetimeManager()); } protected override void InitializeModules() { Manager man= Container.Resolve<Manager>(); } Question is do I need to define my manager object as static in its field to be able to reach its state? Or this is anti pattern or bad for performance?

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  • Guidelines or Design pattern to develop configurable software

    - by Rumit Parakhiya
    I want to develop an application which would have it's own framework, using which developer can implement functionality very easily. Developer shouldn't have to code for each and every page or report. But, he can do it very easily by just configuring it using the framework provided. Some nice examples of it is SAP and Tally. They have got their own framework, using which anybody having knowledge of it can customize or extend functionality of the product. But, as I am beginner in this direction, I don't have any idea about where to start. Can anybody point me to some design pattern which I can follow or some similar open source software which I can refer?

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  • Settings object with singleton pattern

    - by axis
    I need to build an object that will have only one instance because this Object is dedicated to the storage of vital settings for my application and I would like to avoid a misuse of this type or a conflict at run-time. The most popular solution for this, according to the internet, is the Singleton pattern. But I would like to know about other ideas or solutions for this; also I would like to know if other solutions can be much more easy to grasp for an user of this hypothetical library. Thanks.

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  • Singleton Pattern Implementation Issues?

    - by locky28
    Hi I am revising for an exam and need to know some implementation issues with the singleton pattern. they do not need to be too complex just basic things that would affect a developers decision to include them, Thanks P.S. Could any code examples be given in Java thanks.

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  • Design pattern for parsing data that will be grouped to two different ways and flipped

    - by lewisblackfan
    I'm looking for an easily maintainable and extendable design model for a script to parse an excel workbook into two separate workbooks after pulling data from other locations like the command line, and a database. The high level details are as follows. I need to parse an excel workbook containing a sheet that lists unique question names, the only reliable information that can be parsed from the question name is the book code that identifies the title and edition of the textbook the question is associated with, the rest of the question name is not standardized well enough to be reliably parsed by computer. The general form of the question name is best described by the following regular expression. '^(\w+)\s(\w{1,2})\.(\w{1,2})\.(\w{1,3})\.(\w{1,3}\.)*$' The first sub-pattern is the book code, the second sub-pattern is 90% of the time the chapter, and the rest of the sub-patterns could be section, problem type, problem number, or question type information. There is no simple logic, at least not one I can find. There will be a minimum of three other columns in this spreadsheet; one column will be the chapter the question is associated with, the second will be the section within the chapter the question is associated with, and the third will be some kind of asset indicated by a uniform resource locator. 1 | 1 | qname1 | url | description | url | description ... 1 | 1 | qname2 | url | description 1 | 1 | qname3 | url | description | url | description | url | The asset can be indicated by a full or partial uniform resource locator, the partial url will need to be completed before it can be fed into the application. There theoretically could be no limit to the number of asset columns, the assets will be grouped in columns by type. Some times additional data will have to be retrieved from a database or combined with the book code before the asset url is complete and can be understood by the application that will be using the asset. The type is an abstraction, there are eight types right now, each with their own logic in how the uniform resource locator is handled and or completed, and I have to add a new type and its logic every three or four months. For each asset url there is the possibility of a description column, a character string for display in the application, but not always. (I've already worked out validating the description text, and squashing MSs obscure code page down to something 7-bit ascii can handle.) Now that all the details are filled-in I can get to the actual problem of parsing the file. I need to split the information in this excel workbook into two separate workbooks. The first workbook will group all the questions by section in rows. With the first cell being the section doublet and the rest of the cells in the row are the question names. 1.1 | qname1 | qname2 | qname3 | qname4 | 1.2 | qname1 | qname2 | qname3 | 1.3 | qname1 | qname2 | qname3 | qname4 | qname5 There is no set number of questions for each section as you can see from the above example. The second workbook is more complicated, there is one row per asset, and question names that have more than one asset will be duplicated. There will be four or five columns on this sheet. The first is the question name for the asset, the second is a media type used to select the correct icon for the asset in the application, the third is string representing the asset type, the four is the full and complete uniform resource locator for the asset, and the fifth columns is the optional text description for the asset. q1 | mtype1 | atype1 | url | description q1 | mtype2 | atype2 | url | description q1 | mtype2 | atype3 | url | description q2 | mtype1 | atype1 | url | description q2 | mtype2 | atype3 | url | description For the original six types I did have a script that parsed the source excel workbook into the other two excel workbooks, and I was able to add two more types until I ran aground on the implementation of the ninth type and tenth types. What broke my script was the fact that the ninth type is actually a sub-type of one of the original six, but with entirely different logic, and my mostly procedural script could not accommodate without duplicating a lot of code. I also had a lot of bugs in the script and will be writing the test first on this time around. I'm stuck with the format for the resulting two workbooks, this script is glue code, development went ahead with the project without bothering to get a complete spec from the sponsor. I work for the same company as the developers but in the editorial department, editorial is co-sponsor of the project, and am expected to fix pesky details like this (I'm foaming at the mouth as I type this). I've tried factories, I've tried different object models, but each resulting workbook is so different when I find a design that works for generating one workbook the code is not really usable for generating the other. What I would really like are ideas about a maintainable and extensible design for parsing the source workbook into both workbooks with maximum code reuse, and or sympathy.

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  • Advices fo starting a video game design career

    - by Allen Gabriel Baker
    I'm 24 and have a passion for video games and game-design. I've decided I want to design video games as my career. I have no experience with designing video games or coding but I'm interested and willing to learn. I want a job at any level but what would I need to land a job? I have no college experience and I have no money. What is a cheap school, or do I really need to go to school for this, or can I learn on my own? Is it possible to do this with no money? I'm literally broke but I want this so bad I feel like its the only career I'll enjoy. I want to call up company's and ask them what they are looking for in someone they want to hire, is that a good idea? Also I don't know the history of video game design and I don't want to sound like a dummy when someone says something about this field or talks about a famous designer and I have no idea who they're talking about. So what is key info when it comes to this field and where should I find it? Hopefully some of you guys and girls can help me out: I know in the future I will create something everyone will enjoy and you guys will remember when you gave me advice and I will always remember you guys for helping me. I'm gifted I know I am and I want to share my gift with the rest of the world by making games that change the Industry. Help me out please.

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  • Online betting system design [closed]

    - by Rafal
    I am a Computer Science student, preparing for my exam in software engineering. I am strugging with answering one of the sample questions to the scenario below. My understanding is that the system design approach should probably be a mixture of agile and plan driven elements but - since I've no practical experience - it's hard for me to decide on the balance and tolls that should be used. I will appreciate any hints from experienced business analysts who were involved in similar kind of projects. Ray Sing is the owner of “Last Betz", a bookmakers with 7 outlets across Louth and Meath. With the advent of smartphones Ray would now like to allow his clients to place their bets online using their mobile devices. Clients would register for an account and password and would log their credit card details via the Last Betz website. To begin using the facility customers must 'load' their accounts with 100 euros. Any winnings, minus commission, will be placed in the account whilst any losses will be automatically deducted from the account. Assuming you have been selected to develop the above system: How would you approach the design of this system? Discuss the design methods and models you would use.

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  • How effectively "sell" a good design in large meetings

    - by User1
    Many times I have witnessed a sad tragedy. Here's what happens: A team design review for a new project. I see a simple design that has quite a few holes. I casually mention the holes and ways to avoid them. The warnings are ignored with comments like "that 'never' happen in real life" Eventually the things that "will 'never' happen" happen An emergency team design review for a broken project. So what do I do? Copping the "I told you so" attitude is not going to win friends and influence people. Sometimes years go by and the comments from step 3 are forgotten anyway. I definitely don't want to be the annoying pest reminding the world of the gotchas. I often sit back and watch the Titanic sail off to Europe. It's frustrating to see bad designs move forward. It's also frustrating that I can't seem to convince others of the pending peril of the current path. I do worst on team meetings where everyone has different ways of understanding different terms. Also, egos tend to win of reason and thought. I'm looking for good tactics to convince groups people to use some new and complicated ideas.

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  • Design in "mixed" languages: object oriented design or functional programming?

    - by dema80
    In the past few years, the languages I like to use are becoming more and more "functional". I now use languages that are a sort of "hybrid": C#, F#, Scala. I like to design my application using classes that correspond to the domain objects, and use functional features where this makes coding easier, more coincise and safer (especially when operating on collections or when passing functions). However the two worlds "clash" when coming to design patterns. The specific example I faced recently is the Observer pattern. I want a producer to notify some other code (the "consumers/observers", say a DB storage, a logger, and so on) when an item is created or changed. I initially did it "functionally" like this: producer.foo(item => { updateItemInDb(item); insertLog(item) }) // calls the function passed as argument as an item is processed But I'm now wondering if I should use a more "OO" approach: interface IItemObserver { onNotify(Item) } class DBObserver : IItemObserver ... class LogObserver: IItemObserver ... producer.addObserver(new DBObserver) producer.addObserver(new LogObserver) producer.foo() //calls observer in a loop Which are the pro and con of the two approach? I once heard a FP guru say that design patterns are there only because of the limitations of the language, and that's why there are so few in functional languages. Maybe this could be an example of it? EDIT: In my particular scenario I don't need it, but.. how would you implement removal and addition of "observers" in the functional way? (I.e. how would you implement all the functionalities in the pattern?) Just passing a new function, for example?

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  • [C#][Design] Appropriate programming design questions.

    - by Edward
    I have a few questions on good programming design. I'm going to first describe the project I'm building so you are better equipped to help me out. I am coding a Remote Assistance Tool similar to TeamViewer, Microsoft Remote Desktop, CrossLoop. It will incorporate concepts like UDP networking (using Lidgren networking library), NAT traversal (since many computers are invisible behind routers nowadays), Mirror Drivers (using DFMirage's Mirror Driver (http://www.demoforge.com/dfmirage.htm) for realtime screen grabbing on the remote computer). That being said, this program has a concept of being a client-server architecture, but I made only one program with both the functionality of client and server. That way, when the user runs my program, they can switch between giving assistance and receiving assistance without having to download a separate client or server module. I have a Windows Form that allows the user to choose between giving assistance and receiving assistance. I have another Windows Form for a file explorer module. I have another Windows Form for a chat module. I have another Windows Form form for a registry editor module. I have another Windows Form for the live control module. So I've got a Form for each module, which raises the first question: 1. Should I process module-specific commands inside the code of the respective Windows Form? Meaning, let's say I get a command with some data that enumerates the remote user's files for a specific directory. Obviously, I would have to update this on the File Explorer Windows Form and add the entries to the ListView. Should I be processing this code inside the Windows Form though? Or should I be handling this in another class (although I have to eventually pass the data to the Form to draw, of course). Or is it like a hybrid in which I process most of the data in another class and pass the final result to the Form to draw? So I've got like 5-6 forms, one for each module. The user starts up my program, enters the remote machine's ID (not IP, ID, because we are registering with an intermediary server to enable NAT traversal), their password, and connects. Now let's suppose the connection is successful. Then the user is presented with a form with all the different modules. So he can open up a File Explorer, or he can mess with the Registry Editor, or he can choose to Chat with his buddy. So now the program is sort of idle, just waiting for the user to do something. If the user opens up Live Control, then the program will be spending most of it's time receiving packets from the remote machine and drawing them to the form to provide a 'live' view. 2. Second design question. A spin off question #1. How would I pass module-specific commands to their respective Windows Forms? What I mean is, I have a class like "NetworkHandler.cs" that checks for messages from the remote machine. NetworkHandler.cs is a static class globally accessible. So let's say I get a command that enumerates the remote user's files for a specific directory. How would I "give" that command to the File Explorer Form. I was thinking of making an OnCommandReceivedEvent inside NetworkHandler, and having each form register to that event. When the NetworkHandler received a command, it would raise the event, all forms would check it to see if it was relevant, and the appropriate form would take action. Is this an appropriate/the best solution available? 3. The networking library I'm using, Lidgren, provides two options for checking networking messages. One can either poll ReadMessage() to return null or a message, or one can use an AutoResetEvent OnMessageReceived (I'm guessing this is like an event). Which one is more appropriate?

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  • Help to understand the abstract factory pattern

    - by Chobeat
    I'm learning the 23 design patterns of the GoF. I think I've found a way to understand and simplify how the Abstract Factory works but I would like to know if this is a correct assumption or if I am wrong. What I want to know is if we can see the result of the Abstract Factory method as a matrix of possible products where there's a Product for every "Concrete Factory" x "AbstractProduct" where the Concrete Factory is a single implementation among the implementations of an AbstractFactory and an AbstractProduct is an interface among the interfaces to create Products. Is this correct or am I missing something?

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  • Asynchronous update design/interaction patterns

    - by Andy Waite
    These days many apps support asynchronous updates. For example, if you're looking at a list of widgets and you delete one of them then rather than wait for the roundtrip to the server, the app can hide the one you deleted, giving immediate feedback. The actual deletion on the server will happen in the background. This can be seen in web apps, desktop apps, iOS apps, etc. But what about when the background operation fails. How should you feed back to the user? Should you restore the UI to the pre-deletion state? What about when multiple background operations fail together? Does this behaviour/pattern have a name? Perhaps something based on the Command pattern?

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  • Design patterns for effects between actors and technology

    - by changelog
    I'm working on my first game, and taking the opportunity to brush up my C++ (I want to make as much of it as portable as I can.) Whilst working on the technology tree and how it affects actors (spaceships, planets, crew, buildings, etc) I can't find a pattern that decouples these entities enough to feel like a clean approach. Just as an idea, here's the type of effects these actors can have on one another (and techs too) An engineer inside a spaceship boosts its shield A hero in a spaceship in a fleet increases morale A technology improves spaceships' travel distance A building in a planet improves its production The best I can come up with is the Observer pattern, and basically manage it more or less manually (when a crew member enters a spaceship, fire the event; when a new building is built in a planet, fire the event, etc etc.) but it seems to be too tightly coupled to me. I would love to get some ideas about how to approach this better.

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  • design practice for business layer when supporting API versioning

    - by user1186065
    Is there any design pattern or practice recommended for business layer when dealing with multiple API version. For example, I have something like this. http://site.com/blogs/v1/?count=10 which calls business object method GetAllBlogs(int count) to get information http://site.com/blogs/v2/?blog_count=20 which calls business object method GetAllBlogs_v2(int blogCounts) Since parameter name is changed, I created another business method for version 2. This is just one example but it could have other breaking changes for which it requires me to create another method to support both version. Is there any design pattern or best practice for business/data access layer I should follow when supporting API Versioning?

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  • Which parallel pattern to use?

    - by Wim Van Houts
    I need to write a server application that fetches mails from different mail servers/mailboxes and then needs to process/analyze these mails. Traditionally, I would do this multi-threaded, launching a thread for fetching mails (or maybe one per mailbox) and then process the mails. We are moving more and more to servers where we have 8+ cores, so I would like to make use of these cores as much as possible (and not use 1 at 100% and leave the seven others untouched). So conceptually, as an example, it would be nice that I could write the application in such a way that two cores are "continuously" fetching emails and four cores are "continuously" processing/analyzing the emails (since processing and analyzing mails is more CPU intensive than fetching mails). This seems like a good concept, but after studying some parallel patterns, I'm not really sure how this is best implemented. None of the patterns really fit. I'm working in VS2012, native C++, but I guess from a design point of view this does not really matter and just some pointers on how to organize this would be great!

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  • MVC Design Pattern to Combine Multiple Models for use

    - by roverred
    In my design, I have multiple models and each model has a controller. I need to use all the models to process some operation. Most examples I see are pretty simple with 1 view, 1 controller, and 1 model. How would you get all these models together? Only ways I can think of are 1) Have a top-level controller which has a reference to every controller. Those controllers will have a getter/setter function for their model. Does this violate MVC because every controller should have a model? 2) Have an Intermediate class to combine every model into a one model. Then you create a controller for that new super model. Do you know of any better ideas? Thanks.

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  • Another design-related C++ question

    - by Kotti
    Hi! I am trying to find some optimal solutions in C++ coding patterns, and this is one of my game engine - related questions. Take a look at the game object declaration (I removed almost everything, that has no connection with the question). // Abstract representation of a game object class Object : public Entity, IRenderable, ISerializable { // Object parameters // Other not really important stuff public: // @note Rendering template will never change while // the object 'lives' Object(RenderTemplate& render_template, /* params */) : /*...*/ { } private: // Object rendering template RenderTemplate render_template; public: /** * Default object render method * Draws rendering template data at (X, Y) with (Width, Height) dimensions * * @note If no appropriate rendering method overload is specified * for any derived class, this method is called * * @param Backend & b * @return void * @see */ virtual void Render(Backend& backend) const { // Render sprite from object's // rendering template structure backend.RenderFromTemplate( render_template, x, y, width, height ); } }; Here is also the IRenderable interface declaration: // Objects that can be rendered interface IRenderable { /** * Abstract method to render current object * * @param Backend & b * @return void * @see */ virtual void Render(Backend& b) const = 0; } and a sample of a real object that is derived from Object (with severe simplifications :) // Ball object class Ball : public Object { // Ball params public: virtual void Render(Backend& b) const { b.RenderEllipse(/*params*/); } }; What I wanted to get is the ability to have some sort of standard function, that would draw sprite for an object (this is Object::Render) if there is no appropriate overload. So, one can have objects without Render(...) method, and if you try to render them, this default sprite-rendering stuff is invoked. And, one can have specialized objects, that define their own way of being rendered. I think, this way of doing things is quite good, but what I can't figure out - is there any way to split the objects' "normal" methods (like Resize(...) or Rotate(...)) implementation from their rendering implementation? Because if everything is done the way described earlier, a common .cpp file, that implements any type of object would generally mix the Resize(...), etc methods implementation and this virtual Render(...) method and this seems to be a mess. I actually want to have rendering procedures for the objects in one place and their "logic implementation" - in another. Is there a way this can be done (maybe alternative pattern or trick or hint) or this is where all this polymorphic and virtual stuff sucks in terms of code placement?

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  • Convert table base design to table less design in best way

    - by Brij
    What is the best optimized way to convert following in table less design? the layout should be cross browser compatible and SEO Friendly. <table cellpadding="0" cellspacing="0"> <tr> <td>Row 1 Column 1</td> <td>Row 1 Column 2</td> <td>Row 1 Column 3</td> </tr> <tr> <td colspan="3" align="center">Row 2</td> </tr> <tr> <td>Row 3</td> <td align="right" colspan="2"><img src="test.jpg" alt="test" /></td> </tr> </table>

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  • Software Design & Web Service Design

    - by 001
    I'm about to design my Web service API, most of the functions of my API is basically very simular to my web application. Now the question is, should I create 1 single method and reuse them for both the web application and the web service api? (This seems to be the logical solution, however its very complicated; it's much easier to duplicate the method used by the web application, and keep both separate, ie one method for the web application and one method for the web service.) How do you guys do it? 1) REUSE: one main method and reuse them for both web application and web service application (I like this but it's complicated) WebAppMethodX --uses-- COMMONFUNCTIONMETHOD_X APIMethodX ---uses---- COMMONFUNCTIONMETHOD_X ie common function performs functions such as creating/updating/deleting records etc 2) DUPLICATE: two methods, one method for the web application and one method for the web service. WebAppMethodX APIMethodX

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