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  • What triggered the popularity of lambda functions in modern mainstream programming languages?

    - by Giorgio
    In the last few years anonymous functions (AKA lambda functions) have become a very popular language construct and almost every major / mainstream programming language has introduced them or is planned to introduce them in an upcoming revision of the standard. Yet, anonymous functions are a very old and very well-known concept in Mathematics and Computer Science (invented by the mathematician Alonzo Church around 1936, and used by the Lisp programming language since 1958, see e.g. here). So why didn't today's mainstream programming languages (many of which originated 15 to 20 years ago) support lambda functions from the very beginning and only introduced them later? And what triggered the massive adoption of anonymous functions in the last few years? Is there some specific event, new requirement or programming technique that started this phenomenon? IMPORTANT NOTE The focus of this question is the introduction of anonymous functions in modern, main-stream (and therefore, maybe with a few exceptions, non functional) languages. Also, note that anonymous functions (blocks) are present in Smalltalk, which is not a functional language, and that normal named functions have been present even in procedural languages like C and Pascal for a long time. Please do not overgeneralize your answers by speaking about "the adoption of the functional paradigm and its benefits", because this is not the topic of the question.

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  • Class hierarchy problem in this social network model

    - by Gerenuk
    I'm trying to design a class system for a social network data model - basically a link/object system. Now I have roughly the following structure (simplified and only relevant methods shown) class Data: "used to handle the data with mongodb" "can link, unlink data and also return other linked data" "is basically a proxy object that only stores _id and accesses mongodb on requests" "it looks like {_id: ..., _out: [id1, id2,...], _inc: [id3, id4, ...]}" def get_node(self, id) "create a new Data object from the underlying mongodb" "each data object can potentially create a reference object to new mongo data" "this is needed when the data returns the linked objects" class Node: """ this class proxies linking calls to .data it includes additional network logic operations whereas Data only contains a basic database solution """ def __init__(self, data): "the infrastructure realization is stored as composition by an included object data" "Node bascially proxies most calls to the infrastructure object data" def get_node(self, data): "creates a new object of class Object or Link depending on data" class Object(Node): "can have multiple connections to Link" class Link(Node): "has one 'in' and one 'out' connection to an Object" This system is working, however maybe wouldn't work outside Python. Note that after reading links Now I have two questions here: 1) I want to infrastructure of the data storage to be replacable. Earlier I had Data as a superclass of Node so that it provided the neccessary calls. But (without dirty Python tricks) you cannot replace the superclass dynamically. Is using composition therefore recommended? The drawback is that I have to proxy most calls (link, unlink etc). Any thoughts? 2) The class Node contains the common method .get_node which is used to built new Object or Link instances after reading out the data. Some attribute of data decided whether the object which is only stored by id should be instantiated as an Object or Link class. The problem here is that Node needs to know about Object and Link in advance, which seems dodgy. Do you see a different solution? Both Object and Link need to instantiate one of all possible types depending on what the find in their linked data. Are there any other ideas how to implement a flexible Object/Link structure where the underlying database storage is isolated?

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  • Should custom data elements be stored as XML or database entries?

    - by meteorainer
    There are a ton of questions like this, but they are mostly very generalized, so I'd like to get some views on my specific usage. General: I'm building a new project on my own in Django. It's focus will be on small businesses. I'd like to make it somewhat customizble for my clients so they can add to their customer/invoice/employee/whatever items. My models would reflect boilerplate items that all ModelX might have. For example: first name last name email address ... Then my user's would be able to add fields for whatever data they might like. I'm still in design phase and am building this myself, so I've got some options. Working on... Right now the 'extra items' models have a FK to the generic model (Customer and CustomerDataPoints for example). All values in the extra data points are stored as char and will be coerced/parced into their actual format at view building. In this build the user could theoretically add whatever values they want, group them in sets and generally access them at will from the views relavent to that model. Pros: Low storage overhead, very extensible, searchable Cons: More sql joins My other option is to use some type of markup, or key-value pairing stored directly onto the boilerplate models. This coul essentially just be any low-overhead method weather XML or literal strings. The view and form generated from the stored data would be taking control of validation and reoganizing on updates. Then it would just dump the data back in as a char/blob/whatever. Something like: <datapoint type='char' value='something' required='true' /> <datapoint type='date' value='01/01/2001' required='false' /> ... Pros: No joins needed, Updates for validation and views are decoupled from data Cons: Much higher storage overhead, limited capacity to search on extra content So my question is: If you didn't live in the contraints impose by your company what method would you use? Why? What benefits or pitfalls do you see down the road for me as a small business trying to help other small businesses? Just to clarify, I am not asking about custom UI elements, those I can handle with forms and template snippets. I'm asking primarily about data storage and retreival of non standardized data relative to a boilerplate model.

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  • What is the best way to diagrammatically represent a system threading architecture?

    - by thegreendroid
    I am yet to find the perfect way to diagrammatically represent the overall threading architecture for a system (using UML or otherwise). I am after a diagramming technique that would show all the threads in a given system and how they interact with each other. There are a few similar questions - Drawing Thread Interaction, UML Diagrams of Multithreaded Applications and Intuitive UML Approach to Depict Threads but they don't fully answer my question. What are some of the techniques that you've found useful to depict the overall threading architecture for a system?

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  • Is it bad practice for a module to contain more information than it needs?

    - by gekod
    I just wanted to ask for your opinion on a situation that occurs sometimes and which I don't know what would be the most elegant way to solve it. Here it goes: We have module A which reads an entry from a database and sends a request to module B containing ONLY the information from the entry module B would need to accomplish it's job (to keep modularity I just give it the information it needs - module B has nothing to do with the rest of the information from the read DB entry). Now after finishing it's job, module B has to reply to a module C if it succeeded or failed. To do this module B replies with the information it has gotten from module A and some variable meaning success or fail. Now here comes the problem: module C needs to find that entry again BUT the information it has gotten from module B is not enough to uniquely find the exact same entry again. I don't think that module A giving more information to module B which it doesn't need to do it's job but which it could then give back to module C would be a good practice because this would mean giving some module information it doesn't really need. What do you think?

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  • Delivery terminology and order of magnitude

    - by Peter Turner
    What is the standard way of describing how software products are released and the proportionate order of magnitude to which the changes relative to the software product are conveyed? Is Release Update Patch Bug Fix redundant? or Is Update Patch too terse? As an end user I'd think that all bug fixes are patches (insofar as they are not 100% new code) and all patches should be updates (insofar as they don't degrade the product) and all updates should be releases (insofar as they are actually released), but this really doesn't help anyone understand why they need to get them. Then, if the person who makes the software change appends "critical" or "zero-day" in the notes, I would be unwise to leave the changes unapplied.

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  • What would you say to a bunch of software engineering students on their first day at college?

    - by Álvaro
    Next Friday I'm giving a short (30 min.) talk to a bunch of software engineering students who will be attending the same university I did. Some context: The place is Montevideo, Uruguay The university is Universidad de la República (public, free university) The Software Engineering programme takes 5 years (if you're very good and don't start working early). Around 800 new students per year, around 80 graduates per year. Conditions are harsh, particularly the first two years. Most of them probably have no idea what software engineering or programming is. My goal would be to somehow give them an idea of the field and hopefully motivate them to endure the hardships ahead to eventually become successful developers. So the question is: what would you tell these people?

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  • whats the name of this pattern?

    - by Wes
    I see this a lot in frameworks. You have a master class which other classes register with. The master class then decides which of the registered classes to delegate the request to. An example based passed in class may be something this. public interface Processor { public boolean canHandle(Object objectToHandle); public void handle(Object objectToHandle); } public class EvenNumberProcessor extends Processor { public boolean canHandle(Object objectToHandle) { if (!isNumeric(objectToHandle)){ return false } return isEven(objectToHandle); } public void handle(objectToHandle) { //Optionally call canHandleAgain to ensure the calling class is fufilling its contract doSomething(); } } public class OddNumberProcessor extends Processor { public boolean canHandle(Object objectToHandle) { if (!isNumeric(objectToHandle)){ return false } return isOdd(objectToHandle); } public void handle(objectToHandle) { //Optionally call canHandleAgain to ensure the calling class is fufilling its contract doSomething(); } } //Can optionally implement processor interface public class processorDelegator { private List processors; public void addProcessor(Processor processor) { processors.add(processor); } public void process(Object objectToProcess) { //Lookup relevant processor either by keeping a list of what they can process //Or query each one to see if it can process the object. chosenProcessor=chooseProcessor(objectToProcess); chosenProcessor.handle(objectToProcess); } } Note there are a few variations I see on this. In one variation the sub classes provide a list of things they can process which the ProcessorDelegator understands. The other variation which is listed above in fake code is where each is queried in turn. This is similar to chain of command but I don't think its the same as chain of command means that the processor needs to pass to other processors. The other variation is where the ProcessorDelegator itself implements the interface which means you can get trees of ProcessorDelegators which specialise further. In the above example you could have a numeric processor delegator which delegates to an even/odd processor and a string processordelegator which delegates to different strings. My question is does this pattern have a name.

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  • Search network device from LAN through my C++ application and change the IP address

    - by Arun Kumar K S
    I am developing an application in C++ to communicate with my network device. I used UDP classes to search the device from the network. I done the code in such a way that from my application a broadcast message will send to the local network. The device will respond to the broadcast message and the application will get the IP address from that response. After establishing a network communication send a message to the device for changing the IP address. That worked fine if my devices IP address is correct. But when I set a wrong IP address and subnet to the device. My application will never get any messages from the device. So I can't able communicate to the device and not able get the device and unable to change the IP address etc. Say example IP address of the device 20.1.1.1 Subnet Mask 255.0.0.0 And in my system that runs the application IP address 192.168.1.23 Subnet Mask 255.255.255.0 I tried the Lantronix device installation software with their Lantronix device in network. It listed the device from the network and I am able to change the IP address from their software. Any one know how this is done in this type of software? How I can search in network to find the device and change the IP address when its IP address is not in range? Which protocol they used to find the device?

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  • Verification of requirements question

    - by user970696
    Doing a lot of reading about V&V, I would need to clarify the following. A lot of definitons (less formal ones found in books) define verification like that: Verification: The software should conform to its specification. But then they speak about requirement verification, design verification etc. If I say that these items are "software" in terms of applying the definitons, what should I checked them against, what specification should requirements, which is the basic information, conform to? And one more thing: shouldnt be requirements also validated? To make sure they meets the customer needs? All texts I have speak only about SW validation on the end of the dev.process..

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  • Analyzing a programming language

    - by Matt Fenwick
    In SICP, the authors state (Section 1.1) that there are three basic "mechanisms" of programming languages: primitive expressions, which represent the simplest entities the language is concerned with means of combination, by which compound elements are built from simpler ones means of abstraction, by which compound elements can be named and manipulated as units How can I analyze a mainstream programming language (Java, for example) in terms of these elements or mechanisms?

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  • What effects do various drugs have on coding style / productivity? [closed]

    - by codecraft
    Can anyone tell me what the effect of various drugs are on coding style, and if coding on drugs can be more productive, or more fun? Are some types of drugs better suited to certain tasks and phases of software development? And which programming languages are best suited to coding on drugs? It would be great if you could back up your answers by data, probably even code snippets showcasing the effect of the drug experience.

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  • How to detect if an app was already installed before

    - by Dante
    How do software applications keep track of whether the user already installed the application before in it's Windows system? Say you install app X, trial version, remove it, then re install it, and when you run it again it detects you had already installed it before. If you uninstall and clean all registry information it shouldn't know you had already installed it before... Disclaimer: I'm not trying to "hack" any application, just thinking about how this is implemented.

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  • How do you choose to use a specific programming language?

    - by Jesús Bracamonte
    I was having a small talk between teammates about how you choose a programming language for use in a project which lead me to think that there are many criteria to choose one in the beginning of a project but no real standard. Do you chose a programming language for the syntax and semantics? Or do you choose one because it has the best support to do certain things? Or because you have better libraries? Or do you choose it for the paradigm? What criteria do you use to choose one language when you are going to do a project?

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  • How do I explain the importance of NUNIT Test cases to my Colleagues [duplicate]

    - by JNL
    This question already has an answer here: How to explain the value of unit testing 6 answers I am currently working in Software Development for applications including lot of Mathematical Calculations. As a result there are lot of test cases that we need to consider. We donot have any NUNIT Test case system, I am wonderring how should I get the advantages of implementing the NUNIT testing in front of my colleagues and my boss. I am pretty sure, it would be of great help for our team. Any help regarding the same, will be higly appreciated.

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  • What is the difference between development and R&D?

    - by MainMa
    I was asked by a colleague to explain clearly the difference between ordinary development and research and development (R&D) and was unable to do it. After reading Wikipedia, I still don't have the precise answer. According to Wikipedia (slightly modified): There are two primary models: In one model, the primary function is to develop new products; in the other model, the primary function is to discover and create new knowledge about scientific and technological topics for the purpose of uncovering and enabling development of valuable new products, processes, and services. The first model is confusing. Does it mean that development (not R&D) consists exclusively in adding new features to a product, solving bugs and doing maintenance? What if something which was previously developed as a new feature becomes a separate product? The second model is less confusing, but still, how to qualify whether something is new knowledge or existent knowledge which is just rediscovered? Later, Wikipedia adds that ordinary development is different from R&D because of its: nearly immediate profit or immediate improvement. It's still not clear enough. How to qualify "nearly immediate profit"? What if a task has an immediate profit but requires heavy research? Or if it is basic but has uncertain profit, like the enforcement of a common style over the codebase? For example, does it belong to development or R&D to: Develop an engine which abstracts the access to the database, simplifying and shortening enormously the code of other applications (existent or ones which will be written in future) which should access to the database? Establish a new service-oriented architecture for the entire organization of company resources, in order to move from a bunch of separate and autonomous applications to a set of well-organized, interconnected web services, like what is used by Amazon? Design a new communication protocol to allow faster replication of data between two data centers of the company? Conceive a new type of software testing while working on a specific product, knowing that this type of testing will improve/simplify the testing process? Prove that Functional programming is more appropriate than OOP for a specific application, based on evidence, logic and previous experience? Enhance the existent application by adding gestures on tactile screens, after doing studies and testing that shows that those gestures improve the productivity of the users by a ratio of at least 1.4 for a precise set of tasks? Find a way to strongly enhance the Power usage effectiveness (PUE) of a data center? Create a Domain-Specific Language (DSL)? In short, how could I determine whether I'm doing R&D while working on something?

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  • Who owns code if its written by one person with another person directing [on hold]

    - by user136226
    I have an Issue that I need some info on. Basically what Im looking to find out is if I create software,and someone else gives me direction on what they want the software to look like,e.g. an image here,this font of text and it must behave in a certain way. Also some of the code was not developed on my computer and there is no official agreement in place. Not looking to screw anyone over here but need to protect myself if things go sour. Do I own the software or is it jointly owned? Thanks

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  • Is it correct to fix bugs without adding new features when releasing software for system testing?

    - by Pratik
    This question is to experienced testers or test leads. This is a scenario from a software project: Say the dev team have completed the first iteration of 10 features and released it to system testing. The test team has created test cases for these 10 features and estimated 5 days for testing. The dev team of course cannot sit idle for 5 days and they start creating 10 new features for next iteration. During this time the test team found defects and raised some bugs. The bugs are prioritised and some of them have to be fixed before next iteration. The catch is that they would not accept the new release with any new features or changes to existing features until all those bugs fixed. The test team says that's how can we guarantee a stable release for testing if we also introduce new features along with the bug fix. They also cannot do regression tests of all their test cases each iteration. Apparently this is proper testing process according to ISQTB. This means the dev team has to create a branch of code solely for bug fixing and another branch where they continue development. There is more merging overhead specially with refactoring and architectural changes. Can you agree if this is a common testing principle. Is the test team's concern valid. Have you encountered this in practice in your project.

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  • What layer to introduce human readable error messages?

    - by MrLane
    One of the things that I have never been happy with on any project I have worked on over the years and have really not been able to resolve myself is exactly at what tier in an application should human readable error information be retrieved for display to a user. A common approach that has worked well has been to return strongly typed/concrete "result objects" from the methods on the public surface of the business tier/API. A method on the interface may be: public ClearUserAccountsResult ClearUserAccounts(ClearUserAccountsParam param); And the result class implementation: public class ClearUserAccountsResult : IResult { public readonly List<Account> ClearedAccounts{get; set;} public readonly bool Success {get; set;} // Implements IResult public readonly string Message{get; set;} // Implements IResult, human readable // Constructor implemented here to set readonly properties... } This works great when the API needs to be exposed over WCF as the result object can be serialized. Again this is only done on the public surface of the API/business tier. The error message can also be looked up from the database, which means it can be changed and localized. However, it has always been suspect to me, this idea of returning human readable information from the business tier like this, partly because what constitutes the public surface of the API may change over time...and it may be the case that the API will need to be reused by other API components in the future that do not need the human readable string messages (and looking them up from a database would be an expensive waste). I am thinking a better approach is to keep the business objects free from such result objects and keep them simple and then retrieve human readable error strings somewhere closer to the UI layer or only in the UI itself, but I have two problems here: 1) The UI may be a remote client (Winforms/WPF/Silverlight) or an ASP.NET web application hosted on another server. In these cases the UI will have to fetch the error strings from the server. 2) Often there are multiple legitimate modes of failure. If the business tier becomes so vague and generic in the way it returns errors there may not be enough information exposed publicly to tell what the error actually was: i.e: if a method has 3 modes of legitimate failure but returns a boolean to indicate failure, you cannot work out what the appropriate message to display to the user should be. I have thought about using failure enums as a substitute, they can indicate a specific error that can be tested for and coded against. This is sometimes useful within the business tier itself as a way of passing via method returns the specifics of a failure rather than just a boolean, but it is not so good for serialization scenarios. Is there a well worn pattern for this? What do people think? Thanks.

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  • What's the best version control/QA workflow for a legacy system?

    - by John Cromartie
    I am struggling to find a good balance with our development and testing process. We use Git right now, and I am convinced that ReinH's Git Workflow For Agile Teams is not just great for capital-A Agile, but for pretty much any team on DVCS. That's what I've tried to implement but it's just not catching. We have a large legacy system with a complex environment, hundreds of outstanding and undiscovered defects, and no real good way to set up a test environment with realistic data. It's also hard to release updates without disrupting users. Most of all, it's hard to do thorough QA with this process... and we need thorough testing with this legacy system. I feel like we can't really pull off anything as slick as the Git workflow outlined in the link. What's the way to do it?

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  • CS Concentrations and Career Paths

    - by xbonez
    I'm approaching the end of Sophomore year in college (Studying Computer Science), and very soon I'm going to have to decide on my concentration, but I honestly don't know what each concentration means. I basically have two questions: 1. How much influence does your concentration have on your career path? For example, would a video game development company only look at people with a concentration in Game Development? 2.It would be great if you guys could, in a line or two, tell me what sort of jobs am I looking at for each of the concentrations? I need to pick at least two of the 9 below. - Algorithms and Data Structures - Artificial Intelligence - Computer and Network Society - Computer graphics and vision - Human-Computer Interaction - Game Development and Design - Numeric and Symbolic Computation - Programming languages - Systems

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  • how to save and load the state of a game in scheme

    - by user3667664
    I'm creating the game of chess in scheme, but do not know how to save and load game state is a part I have this code (define-struct ficha(color se-movio? tipo-ficha )) ;;tablero lista de listas de fichas (define-struct estado (tablero turno fichaSel)) (define bpawn (bitmap "b-peon.png")) (define brook (bitmap "b-torre.png")) (define bcaballo (bitmap "b-caballo.png")) (define bbish (bitmap "b-arfil.png")) (define bquee (bitmap "b-reina.png")) (define bking (bitmap "b-rey.png")) (define wpawn (bitmap "w-peon.png")) (define wrook (bitmap "w-torre.png")) (define wcaballo (bitmap "w-caballo.png")) (define wbish (bitmap "w-arfil.png")) (define wquee (bitmap "w-reina.png")) (define wking (bitmap "w-rey.png")) (define board (bitmap "board.jpg")) This is the board that is a list of lists (define tableroini (list (list torreb caballob arfilb reinab reyb arfilb caballob torreb) (list peonb peonb peonb peonb peonb peonb peonb peonb) (list empty empty empty empty empty empty empty empty) (list empty empty empty empty empty empty empty empty) (list empty empty empty empty empty empty empty empty) (list empty empty empty empty empty empty empty empty) (list peonw peonw peonw peonw peonw peonw peonw peonw) (list torrew caballow arfilw reinaw reyw arfilw caballow torrew))) I did this to save the state of the game: (define (Guardar-en-archivo archivo) (write-file (string-append Subcarpeta archivo ".txt") "game state" )) But not as you insert the game state on "game state" for me to save the game How I can do this ?

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  • What is the most effective order to learn SQL Server, LINQ, and Entity Framework?

    - by user1525474
    I am trying to get some advice on what order I should learn about SQL Server, LINQ, and Entity Framework to be able to better work with ASP.NET Webforms and MVC. From what I've been able to learn so far, many recommend learning LINQ or Entity Framework before learning SQL Server. It also appears that many companies are looking for people with knowledge in LINQ-to-SQL and Entity Framework without mentioning SQL Server. However, my understanding is that LINQ-to-SQL and Entity Framework translate code into SQL Server queries, making this a poor approach. Is there a correct or best order in which to learn these technologies?

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  • Company wants to write custom project management tool, rather then use third party product.

    - by Jason Evans
    At the company I work, we are really wanting to get into the agile methodology for developing software. One thing that I'm not excited about is the fact that management wants us to build a custom project management feature inside the company's Intranet. I think this is a total waste of time. There are many great third party tools available (e.g. Axosoft OnTime) that can do everything we need, and more. For how much development time it would cost us to build our own project management module, we could buy numerous licences for a third party product. One concern is that, whilst we are writing code for a client, and using our custom Intranet project management module, we find bugs in the module that need fixing ASAP. That means having to stop work on the client code to fix the Intranet. That just puts shivers down my spine. Another worry I have is lack of functionality. This custom module is going to be so basic, that it will just feel really crap to use. That might sound a bit snooty, but for goodness sake, many third party tools are so feature rich, that the idea of having to write our own tool makes feel very uneasy. In fact, I can't be bothered. What do you guys think? I'm going to raise this issue with my boss, since I feel it's such an important topic to talk about. EDIT: Thanks for the great responses, much appreciated. To summarize some of them: Money Naturally my boss does want to save money, by not forking out a few hundred £'s for licences. However, for us to write a custom tool, it will take x number of days, multiplied by approx £500, which is our costs. I don't see the business value in this. Management have mentioned that they want to sell the Intranet as a product in the future, but it's so custom to our needs (and downright basic), that in order to give it to another client, I can see us having to fork a version of the code and rebuild the majority of it anyway. So it's not like we're gaining anything there in reuse. Features Having our own custom module means not feature bloat - only the functionality we require will be in the product. My issue is that there are plenty of free, open-source project management tools out there with minimal features already. So even if cost is an issue, we could look into open-source. Again it all boils down to the fact that I don't see the point in writing a project management tool in this day and age. It's a bit like writing your own web browser - why?, what's the point? Although management are asking for this tool, just because they are, it does not mean I'm going to please them and do it just because they asked for it. If something does not make sense, then I will raise it as a concern. At the end of the day, it's the developers who write the code, it's the developers who make money for a business. Thus, as far I'm concerned, the devs have a very big role in deciding how a company should manage projects and what tools are used. "I am Spartan, argh!" :) Hmm, I've not been able to make this question a wiki for some reason, thus I'm going to have to pick an answer to accept. Cheers. Jas.

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  • Database ERD design: 2 types user in one table

    - by Giskin Leow
    I have read this (Database design: 3 types of users, separate or one table?) I decided to put admin and normal user in one table since the attributes are similar: fullname, address, phone, email, gender ... Then I want to draw ERD, suddenly my mind pop out a question. How to draw? Customer make appointment and admin approve appointment. now only two tables, and admin, customer in same table. Help.

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