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• Relationship DAO, Servlet, JSP and POJO

  - by John Hendrik

  I want to implement a JSP, POJO, DAO and Servlet in my J2EE program. However, I don't fully understand how the relationship between these elements should be. Is the following (MVC) setup the right way to do it? Main class creates servlet(controller) Servlet has a DAO defined in its class DAO has a POJO defined in its class Servlet communicates with the view (JSP page) Please give your feedback.

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• Where should libraries be placed, in windows?

  - by Gabriel Diaconescu

  I have just moved from Linux to Windows, and I have to use the Zend Framework library. Where should the library be placed? Directly on C drive Create a lib folder like C:/lib/ Create a lib folder in my user folder I am wondering if there is a classic folder where these kind of libraries are placed. Update:I am asking about the location on my own standpoint. The Zend Framework library is a PHP framework.

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• how do you remember programming related stuff?

  - by dan leadgy

  How do you remember programming related stuff? Did you get the feeling you did encounter the error you have now a few years ago and you could swear you knew the cause but now you forgot it? Did you work with the xsl's string parsing some time ago but now you can't remember exactly which are the string functions altogether from xsl and you have to start from scratch? Or perhaps you forget about some feature from Apache Commons like "filtering a collection by some predicate" that you surely used in the past. So how do you do it? I tried having a blog but when I develop apps, I never find the time to update the blog or write about my experiences. Also, using a wiki is a nice thing but then I found it difficult to keep a clean separation between them since many times I needed to change a blog post to add new information about that topic. This made me think that I actually should have put this topic in the wiki instead of the blog. Do you have any systems that help you remember about your programming experience? What's your setup?

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• Implementing a bit shift using AND, NOT, ADD [closed]

  - by fdart17

  I'm implementing a 16-bit left bit shift by r bits, and I only have access to AND, NOT and ADD. There are 3 condition codes, negative, zero and positive, which are set when you use any of these operations. How I went about it was : (1) And the number with 1000 0000 0000 0000 to set condition codes to positive if the most significant bit is 1. (2) Add the number with itself. This shifts bits one to the left. (3) If the MSB was 1, add 1 to the result. (4) Loop threw (1)-(3) r times. I'm wondering if anyone has any hints to some more efficient methods? Thanks!

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• What are the advantages of programming to under an OS as opposed to bare metal executive?

  - by gby

  Assume you are presented with an embedded system application to program, in C, on a multi-core environment (think a Cavium or Tilera) and need to choose between two environments: Code the application under Linux in SMP mode or code the application under a thin bare metal executive (something like a very minimal RTOS), perhaps with a single core running UP Linux that can serve control tasks. For the purpose of this question, assume that both environment provide the same level of performance guarantees in any measurable aspects of run time performance, including number of meaningful action per second, jitter, latency, real time considerations - the works. (and yes, I realize this is by far not a trivial assumption at all, bare with me). How would you justify going with a Linux SMP based solution rather then a bare metal thin executive solution? The question may seems silly. It certainly seems obvious to me - but I have to convince someone that does not think the same. Could you help make a list of arguments in favor of choosing a real SMP aware OS (Linux) vs. a bare metal executive assuming performance guarantees are NOT an issue? Many thanks

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• Can you point me to a nontrivial strategy pattern implementation?

  - by Eugen Martynov

  We are faced implementing a registration workflow with many branches. There are three main flows which in some conditions lead to one another. Each flow has at least four different steps; some steps interact with the server, and every step adds more information to the state. Also the requirement is to have it persistent between sessions, so if the user closes the app (this is a mobile app), it will restore the process from the last completed step with the state from the previous session. I think this could benefit from the use of the strategy pattern, but I've never had to implement it for such a complex case. Does anyone know of any examples in open source or articles from which I could find inspiration? Preferably the examples would be from a live/working/stable application. I'm interested in Java implementation mostly; we are developing for Java mobile phones: android, blackberry and J2ME. We have an SDK which is quite well separated from platform specific implementations, but examples in C++, C#, Objective-C or Python would be acceptable.

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• Authenticating users for a website

  - by MCB

  I'm working on a website and I want to validate that an individual is an employee at one of a large number of companies (probably using their company's email address, which I don't know before hand). The idea being some users are the general public and others are from these companies. And I need some way to authenticate that the users claiming to be employees are being honest while still having a friendly enough UI. I did an informal survey of people I know and the domains and emails will match in a majority of cases but they might not always match exactly so you might have a company with a website foo.com and an email [email protected] (although foobar.com did redirect back to foo.com). And while I can easily check that I'm not sure what other variations might be out there (maybe fooLA.com and email [email protected], etc.)

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• Building a chat-like functionality in iOS

  - by Mani BAtra

  I was planning to implement a functionality wherein a user can send data to a friend of his, similar to sending messages in WhatsApp. This is how I broke down the problem : The user registers for the app. This equates to user info being stored on a dedicated server. With the phone number as the key identifier. The user selects the friend to send a message to and pushes the data. The receiver polls the server regularly and acknowledges that the data has been received. I did a little bit of research and am thinking of implementing this using the XMPP Framework for iOS. Any pointers as to is this the correct implementation or some advice in general?

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• Erlang web frameworks survey

  - by Zachary K

  (Inspired by similar question on Haskel) There are several web frameworks for Erlang like Nitrogen, Chicago Boss, and Zotonic, and a few more. In what aspects do they differ from each other? For example: features (e.g. server only, or also client scripting, easy support for different kinds of database) maturity (e.g. stability, documentation quality) scalability (e.g. performance, handy abstraction) main targets Also, what are examples of real-world sites / web apps using these frameworks? EDIT: Starting a bounty in hopes that it will get some conversation going

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• How can I keep directories in sync

  - by Guillaume Boudreau

  I have a directory, dirA, that users can work in: they can create, modify, rename and delete files & sub-directores in dirA. I want to keep another directory, dirB, in sync with dirA. What I'd like, is a discussion on finding a working algorithm that would achieve the above, with the limitations listed below. Requirements: 1. Something asynchronous - I don't want to stop file operations in dirA while I work in dirB. 2. I can't assume that I can just blindly rsync dirA to dirB on regular interval - dirA could contain millions of files & directories, and terrabytes of data. Completely walking the dirA tree could take hours. Those two requirements makes this really difficult. Having it asynchronous means that when I start working on a specific file from dirA, it might have moved a lot since it appeared. And the second limitation means that I really need to watch dirA, and work on atomic file operations that I notice. Current (broken) implementation: 1. Log all file & directory operations in dirA. 2. Using a separate process, read that log, and 'repeat' all the logged operations in dirB. Why is it broken: echo 1 > dirA/file1 # Allow the 'log reader' process to create dirB/file1: log = "write dirA/file1"; action = cp dirA/file1 dirB/file1; result = OK echo 1 > dirA/file2 mv dirA/file1 dirA/file3 mv dirA/file2 dirA/file1 rm dirA/file3 # End result: file1 contains '1' # 'log reader' process starts working on the 4 above file operations: log = "write file2"; action = cp dirA/file2 dirB/file2; result = failed: there is no dirA/file2 log = "rename file1 file3"; action = mv dirB/file1 dirB/file3; result = OK log = "rename file2 file1"; action = mv dirB/file2 dirB/file1; result = failed: there is no dirB/file2 log = "delete file3"; action = rm dirB/file3; result = OK # End result in dirB: no more files! Another broken example: echo 1 > dirA/dir1/file1 mv dirA/dir1 dirA/dir2 # 'log reader' process starts working on the 2 above file operations: log = "write file1"; action = cp dirA/dir1/file1 dirB/dir1/file1; result = failed: there is no dirA/dir1/file1 log = "rename dir1 dir2"; action = mv dirB/dir1 dirB/dir2; result = failed: there is no dirA/dir1 # End result if dirB: nothing!

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• AJAX driven "page complete" function? Am I doing it right?

  - by Julian H. Lam

  This one might get me slaughtered, since I'm pretty sure it's bad coding practice, so here goes: I have an AJAX driven site which loads both content and javascript in one go using Mootools' Request.HTML. Since I have initialization scripts that need to be run to finish "setting up" the template, I include those in a function called pageComplete(), on every page Visiting one page to another causes the previous pageComplete() function to no longer apply, since a new one is defined. The javascript function that loads pages dynamically calls pageComplete() blindly when the AJAX call is completed and is loaded onto the page: function loadPage(page, params) { // page is a string, params is a javascript object if (pageRequest && pageRequest.isRunning) pageRequest.cancel(); pageRequest = new Request.HTML({ url: '<?=APPLICATION_LINK?>' + page, evalScripts: true, onSuccess: function(tree, elements, html) { // Empty previous content and insert new content $('content').empty(); $('content').innerHTML = html; pageComplete(); pageRequest = null; } }).send('params='+JSON.encode(params)); } So yes, if pageComplete() is not defined in one the pages, the old pageComplete() is called, which could potentially be disastrous, but as of now, every single page has pageComplete() defined, even if it is empty. Good idea, bad idea?

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• How do I know when should I package my classes in Ruby?

  - by Omega

  In Ruby, I'm creating a small game development framework. Just some personal project - a very small group of friends helping. Now I am in need of handling geometric concepts. Rectangles, Circles, Polygons, Vectors, Lines, etc. So I made a class for each of these. I'm stuck deciding whether I should package such classes in a module, such as Geometry. So I'd access them like Geometry::Rectangle, or just Rectangle if I include the module. Now then, my question isn't about this specific scenario. I'd like to know, when is it suitable to package similar classes into one module in Ruby? What factors should I consider? Amount of classes? Usage frequency? Complexity?

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• Examples of datecentric LOB-application in Silverlight with creative design?

  - by Alexander Galkin

  I am a database developer and I have rather limited experience with interface design. I am currently working on a project in my free-time a freetime which is mostly data centric and I would like to develop an eye-catchy interface for it using Silverlight. What I am looking for are examples of nice and interesting LOB applications in Siverlight without the use of paid frameworks. So far, I could only find something like Telerik sample application, but it uses a lot of Telerik controls I can't afford to buy.

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• Is it OK to use dynamic typing to reduce the amount of variables in scope?

  - by missingno

  Often, when I am initializing something I have to use a temporary variable, for example: file_str = "path/to/file" file_file = open(file) or regexp_parts = ['foo', 'bar'] regexp = new RegExp( regexp_parts.join('|') ) However, I like to reduce the scope my variables to the smallest scope possible so there is less places where they can be (mis-)used. For example, I try to use for(var i ...) in C++ so the loop variable is confined to the loop body. In these initialization cases, if I am using a dynamic language, I am then often tempted to reuse the same variable in order to prevent the initial (and now useless) value from being used latter in the function. file = "path/to/file" file = open(file) regexp = ['...', '...'] regexp = new RegExp( regexp.join('|') ) The idea is that by reducing the number of variables in scope I reduce the chances to misuse them. However this sometimes makes the variable names look a little weird, as in the first example, where "file" refers to a "filename". I think perhaps this would be a non issue if I could use non-nested scopes begin scope1 filename = ... begin scope2 file = open(filename) end scope1 //use file here //can't use filename on accident end scope2 but I can't think of any programming language that supports this. What rules of thumb should I use in this situation? When is it best to reuse the variable? When is it best to create an extra variable? What other ways do we solve this scope problem?

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• Single Responsibility Principle Implementation

  - by Mike S

  In my spare time, I've been designing a CMS in order to learn more about actual software design and architecture, etc. Going through the SOLID principles, I already notice that ideas like "MVC", "DRY", and "KISS", pretty much fall right into place. That said, I'm still having problems deciding if one of two implementations is the best choice when it comes to the Single Responsibility Principle. Implementation #1: class User getName getPassword getEmail // etc... class UserManager create read update delete class Session start stop class Login main class Logout main class Register main The idea behind this implementation is that all user-based actions are separated out into different classes (creating a possible case of the aptly-named Ravioli Code), but following the SRP to a "tee", almost literally. But then I thought that it was a bit much, and came up with this next implementation class UserView extends View getLogin //Returns the html for the login screen getShortLogin //Returns the html for an inline login bar getLogout //Returns the html for a logout button getRegister //Returns the html for a register page // etc... as needed class UserModel extends DataModel implements IDataModel // Implements no new methods yet, outside of the interface methods // Haven't figured out anything special to go here at the moment // All CRUD operations are handled by DataModel // through methods implemented by the interface class UserControl extends Control implements IControl login logout register startSession stopSession class User extends DataObject getName getPassword getEmail // etc... This is obviously still very organized, and still very "single responsibility". The User class is a data object that I can manipulate data on and then pass to the UserModel to save it to the database. All the user data rendering (what the user will see) is handled by UserView and it's methods, and all the user actions are in one space in UserControl (plus some automated stuff required by the CMS to keep a user logged in or to ensure that they stay out.) I personally can't think of anything wrong with this implementation either. In my personal feelings I feel that both are effectively correct, but I can't decide which one would be easier to maintain and extend as life goes on (despite leaning towards Implementation #1.) So what about you guys? What are your opinions on this? Which one is better? What basics (or otherwise, nuances) of that principle have I missed in either design?

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• What ever happened to the Google AJAX Search API

  - by John

  I am looking to query the main Google search however all references including stackoveflow point to the Google AJAX Search API. The odd thing is that it does not seem to exist any more not even a note to say it is depreciated? The old links point to main Google code site. If I look at the list of API's on that site the API it replaced is there Web Search API (Deprecated) which links back to same page but not the Google AJAX Search API. Further Google searching is not being helpful either, many blog posts pointing to the same Google site (http://code.google.com/apis/ajaxsearch/) that has no content and redirects to the same place? Just to prove it did exist I have found it on the way back machine however the last snapshot did not show any special unusual message.

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• Basics of ERP for dummies

  - by DarenW

  A situation has arisen where (if I don't scream and run away) I will be involved in an ERP system. This project will be using OpenERP specifically. My background is entirely science/engineering/music/games/art/whatever. I've never set foot in the realm of business systems or anything describable with the word "enterprise". What is a good introduction to the whole ERP concept, OpenERP and business systems in general suitable for those with flat zero experience in that world? The ideal intro would explain, from no assumptions, what the main ideas are, terminology, they style of work and thinking of people in that world, and maybe some concrete suggestions how one can tinker around with a copy of OpenERP to gain basic familiarity.

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• Should I start MCPD training now or wait for new exams?

  - by lunchmeat317

  i apologize if this question has been asked before, or if this is the wrong place to put it. I'm beginning my study track for the MCPD certification in Web Development. However, Microsoft plans to retire this certification on July 31st of 2013, along with two of the necessary tests to receive the certification. On MS's site, I can't find a newer certification path to take - I imagine that Microsoft will release new certification paths and new tests for their new software, but I don't know when that will happen. I don't really know anything about Microsoft's process, as this is the first Microsoft certification I'll be studying for. The bottom line is this - I don't want to lose six months waiting for a new test to appear that won't expire, but I don't want to rush to get a certification that will be invalid in six months (or have to reset any progress due to new study material). To those with experience in affairs like this - what is the best course to take, and can I maximize the time I have now (not wait for new testing material)? Is there any way to find material for the new tests that Microsoft will be rolling out? Thank you for your patience. If this is the wrong place to put this question, I would like to request that it be moved to the correct StackExchange site instead of being closed. Thanks for your help!

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• What is the point of dynamic allocation in C++?

  - by Aerovistae

  I really have never understood it at all. I can do it, but I just don't get why I would want to. For instance, I was programming a game yesterday, and I set up an array of pointers to dynamically allocated little enemies in the game, then passed it to a function which updates their positions. When I ran the game, I got one of those nondescript assertion errors, something about a memory block not existing, I don't know. It was a run-time error, so it didn't say where the problem was. So I just said screw it and rewrote it with static instantiation, i.e.: while(n<4) { Enemy tempEnemy = Enemy(3, 4); enemyVector.push_back(tempEnemy); n++; } updatePositions(&enemyVector); And it immediately worked perfectly. Now sure, some of you may be thinking something to the effect of "Maybe if you knew what you were doing," or perhaps "n00b can't use pointers L0L," but frankly, you really can't deny that they make things way overcomplicated, hence most modern languages have done away with them entirely. But please-- someone -- What IS the point of dynamic allocation? What advantage does it afford? Why would I ever not do what I just did in the above example?

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• How can I reduce the amount of time it takes to fully regression test an application ready for release?

  - by DrLazer

  An app I work on is being developed with a modified version of scrum. If you are not familiar with scrum, it's just an alternative approach to a more traditional watefall model, where a series of features are worked on for a set amount of time known as a sprint. The app is written in C# and makes use of WPF. We use Visual C# 2010 Express edition as an IDE. If we work on a sprint and add in a few new features, but do not plan to release until a further sprint is complete, then regression testing is not an issue as such. We just test the new features and give the app a good once over. However, if a release is planned that our customers can download - a full regression test is factored in. In the past this wasn't a big deal, it took 3 or 4 days and the devs simply fix up any bugs found in the regression phase, but now, as the app is getting larger and larger and incorporating more and more features, the regression is spanning out for weeks. I am interested in any methods that people know of or use that can decrease this time. At the moment the only ideas I have are to either start writing Unit Tests, which I have never fully tried out in a commercial environment, or to research the possibilty of any UI Automation API's or tools that would allow me to write a program to perform a series of batch tests. I know literally nothing about the possibilities of UI automation so any information would be valuable. I don't know that much about Unit testing either, how complicated can the tests be? Is it possible to get Unit tests to use the UI? Are there any other methods I should consider? Thanks for reading, and for any advice in advance. Edit: Thanks for the information. Does anybody know of any alternatives to what has been mentioned so far (NUnit, RhinoMocks and CodedUI)?

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• Library Organization in .NET

  - by Greg Ros

  I've written a .NET bitwise operations library as part of my projects (stuff ranging from get MSB set to some more complicated bitwise transformations) and I mean to release it as free software. I'm a bit confused about a design aspect of the library, though. Many of the methods/transformations in the library come with different endianness. A simple example is a getBitAt method that regards index 0 as the least significant bit, or the most significant bit, depending on the version used. In practice, I've found that using separate functions for different endianness results in much more comprehensible and reusable code than assuming all operations are little-endian or something. I'm really stumped regarding how best to package the library. Should I have methods that have LE and BE versions take an enum parameter in their signature, e.g. Endianness.Little, Endianness.Big? Should I have different static classes with identically named methods? such as MSB.GetBit and LSB.GetBit On a much wider note, is there a standard I could use in cases like this? Some guide? Is my design issue trivial? I have a perfectionist bent, and I sometimes get stuck on tricky design issues like this... Note: I've sort of realized I'm using endianness somewhat colloquially to refer to the order/place value of digital component parts (be they bits, bytes, or words) in a larger whole, in any setting. I'm not talking about machine-level endianness or serial transmission endianness. Just about place-value semantics in general. So there isn't a context of targeting different machines/transmission techniques or something.

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• Books / blogs that discuss service excellence? [closed]

  - by Bogdan Gavril

  I'm looking for information about service excellence topics such as: 0 downtime deployment how to deal with versioning (backward and forward compatibility) environment strategies (how many staging envs ? etc.) performance testing testing in production monitoring I am looking at the Microsoft stack, but the concepts should be the same everywhere. Do you have any recommendations of books or blogs on the subject? PS: I have found some good articles from I.M.Wright's "Hard Code" blog. Anything else?

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• Is there a theory for "transactional" sequences of failing and no-fail actions?

  - by Ross Bencina

  My question is about writing transaction-like functions that execute sequences of actions, some of which may fail. It is related to the general C++ principle "destructors can't throw," no-fail property, and maybe also with multi-phase transactions or exception safety. However, I'm thinking about it in language-neutral terms. My concern is with correctly designing error handling in C++ functions that must be reliable. I would like to know what the concepts below are called so that I can learn more about them. I'm sorry that I can't ask the question more directly. Since I don't know this area I have provided an example to explain my question. The question is at the end. Here goes: Consider a sequence of steps or actions executed sequentially, where actions belong to one of two classes: those that always succeed, and those that may fail. In the examples below: S stands for an action that always succeeds (called "no-fail" in some settings). F stands for an action that may fail (for example, it might fail to allocate memory or do I/O that could fail). Consider a sequences of actions (executed sequentially from left to right): S->S->S->S Since each action in the sequence above succeeds, the whole sequence succeeds. On the other hand, the following sequence may fail because the last action may fail: S->S->S->F So, claim: a sequence has the no-fail (S) property if and only if all of its actions are no-fail. Now, I'm interested in action sequences that form "atomic transactions", with "failure atomicity," i.e. where either the whole sequence completes successfully, or there is no effect. I.e. if some action fails, the earlier ones must be rolled back. This requires that any successfully executed actions prior to a failing action must always be able to be rolled back. Consider the sequence: S->S->S->F S<-S<-S In the example above, the first row is the forward path of the transaction, and the second row are inverse actions (executed from right to left) that can be used to roll back if the final top row actions fails. It seems to me that for a transaction to support failure atomicity, the following invariant must hold: Claim: To support failure atomicity (either completion or complete roll-back on failure) all actions preceding the latest failable (F) action on the forward path (marked * in the example below) must have no-fail (S) inverses. The following is an example of a sequence that supports failure atomicity: * S->F->F->F S<-S<-S Further, if we want the transaction to be able to attempt cancellation mid-way through, but still guarantee either full completion or full rollback then we need the following property: Claim: To support failure atomicity and cancellation mid-way through execution, in the face of errors in the inverse (cancellation) path, all actions following the earliest failable (F) inverse on the reverse path (marked *) must be no-fail (S). F->F->F->S->S S<-S<-F<-F * I believe that these two conditions guarantee that an abortable/cancelable transaction will never get "stuck". My questions are: What is the study and theory of these properties called? are my claims correct? and what else is there to know? UPDATE 1: Updated terminology: what I previously called "robustness" is called atomicity in the database literature. UPDATE 2: Added explicit reference to failure atomicity, which seems to be a thing.

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• How to set-up a simple subversion workflow

  - by Milen Bilyanov

  I am trying to set-up a simple SVN workflow at home. I am new to subversion (and programming) so I have been reading the official PDF documentations but still not sure about how to set-up my repository. I am working mainly with python, bash and rsl (Renderman Shading Language) So I already have a /dev structure on my disk as this: http://imageshack.us/f/708/devstructure.png/ And I have a /site structure that links to my /dev folder: http://imageshack.us/f/651/sitestructure.png/ So obviously starting to use SVN will change this approach that I already have in place. The question is when I am setting-up my SVN repository for the work I do in my /dev folder: Will I set-up a separate repository for each different programming platform? and Where exactly I should be placing my repository? Thanks.

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• How to provide value?

  - by Francisco Garcia

  Before I became a consultant all I cared about was becoming a highly skilled programmer. Now I believe that what my clients need is not a great hacker, coder, architect... or whatever. I am more and more convinced every day that there is something of greater value. Everywhere I go I discover practices where I used to roll my eyes in despair. I saw the software industry with pink glasses and laughed or cried at them depending on my mood. I was so convinced everything could be done better. Now I believe that what my clients desperately need is finding a balance between good engineering practices and desperate project execution. Although a great design can make a project cheap to maintain thought many years, usually it is more important to produce quick fast and cheap, just to see if the project can succeed. Before that, it does not really matters that much if the design is cheap to maintain, after that, it might be too late to improve things. They need people who get involved, who do some clandestine improvements into the project without their manager approval/consent/knowledge... because they are never given time for some tasks we all know are important. Not all good things can be done, some of them must come out of freewill, and some of them must be discussed in order to educate colleagues, managers, clients and ourselves. Now my big question is. What exactly are the skills and practices aside from great coding that can provide real value to the economical success of software projects? (and not the software architecture alone)

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