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  • Modelling problem - Networked devices with commands

    - by Schneider
    I encountered a head scratching modelling problem today: We are modelling a physical control system composed of Devices and NetworkDevices. Any example of a Device is a TV. An example of a NetworkDevice is an IR transceiver with Ethernet connection. As you can see, to be able to control the TV over the internet we must connect the Device to the NetworkDevice. There is a one to many relationship between Device and NetworkDevice i.e. TV only has one NetworkDevice (the IR transceiver), but the IR transceiver may control many Devices (e.g. many TVs). So far no problem. The complicated bit is that every Device has a collection of Commands. The type of the Command (e.g IrCommand, SerialCommand - N.B. not currently modelled) depends on the type of NetworkDevice that the Device is connected to. In the current legacy system the Device has a collection of generic Commands (no typing) where fields are "interpreted" depending on the NetworkDevice type. How do I go about modelling this in OOP such that: You can only ever add a Command of the appropriate type, given the NetworkDevice the Device is attached to? If I change the NetworkDevice the Commands collection changes to the appropriate type Make it so the API is simple/elegant/intuitive to use

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  • Model login constraints based on time

    - by DaDaDom
    Good morning, for an existing web application I need to implement "time based login constraints". It means that for each user, later maybe each group, I can define timeslots when they are (not) allowed to log in into the system. As all data for the application is stored in database tables, I need to somehow create a way to model this idea in that way. My first approach, I will try to explain it here: Create a tree of login constraints (called "timeslots") with the main "categories", like "workday", "weekend", "public holiday", etc. on the top level, which are in a "sorted" order (meaning "public holiday" has a higher priority than "weekday") for each top level node create subnodes, which have a finer timespan, like "monday", "tuesday", ... below that, create an "hour" level: 0, 1, 2, ..., 23. No further details are necessary. set every member to "allowed" by default For every member of the system create a 1:n relationship member:timeslots which defines constraints, e.g. a member A may have A:monday-forbidden and A:tuesday-forbidden Do a depth-first search at every login and check if the member has a constraint. Why a depth first search? Well, I thought that it may be that a member has the rules: A:monday->forbidden, A:monday-10->allowed, A:mondey-11->allowed So a login on monday at 12:30 would fail, but one at 10:30 succeed. For performance reasons I could break the relational database paradigm and set a flag for every entry in the member-to-timeslots-table which is set to true if the member has information set for "finer" timeslots, but that's a second step. Is this model in principle a good idea? Are there existing models? Thanks.

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  • FWA for CSS based sites

    - by weotch
    Does anyone have a favorite style site that posts the latest and greatest sites constructed with CSS + HTML + JS? I'm thinking of something like thefwa.com but not for all flash microsites. Trying to find the definitive portal.

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  • C++ classes with members referencing each other

    - by Saad Imran.
    I'm trying to write 2 classes with members that reference each other. I'm not sure if I'm doing something wrong or it's just not possible. Can anyone help me out here... Source.cpp #include "Headers.h" using namespace std; void main() { Network* network = new Network(); system("pause"); return; } Headers.h #ifndef Headers_h #define Headers_h #include <iostream> #include <vector> #include "Network.h" #include "Router.h" #endif Network.h #include "Headers.h" class Network { protected: vector<Router> Routers; }; Router.h #include "Headers.h" class Router { protected: Network* network; public: }; The errors I'm getting are: error C2143: syntax error : missing ';' before '<' error C2238: unexpected token(s) preceding ';' error C4430: missing type specifier - int assumed. I'm pretty sure I'm not missing any semicolons or stuff like that. The program works find if I take out one of the members. I tried finding similar questions and the solution was to use pointers, but that's what I'm doing and it does't seem to be working!

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  • Create My own language with "Functional Programming Language"

    - by esehara
    I prefer Haskell. I already know How to create my own language with Procedural Language (for example: C, Java, Python, etc). But, I know How to create my own language with Functional Language (for example Haskell, Clojure and Scala). I've already read: Internet Resources Write Yourself a Scheme in 48 Hours Real World Haskell - Chapter 16.Using Persec Writing A Lisp Interpreter In Haskell Parsec, a fast combinator parser Implementing functional languages: a tutorial Books Introduction Functional Programming Using Haskell 2nd Edition -- Haskell StackOverflow (but with procedural language) Learning to write a compiler create my own programming language Source Libraries and tools/HJS -- Haskell Are there any other good sources? I wants to get more links,or sources.

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  • LockWorkStation - Compilation error - identifier not found

    - by Microkernel
    Hi All, I am writing an application in which I got to lock the computer screen (OS is Windows). My Application is in C++. For this purpose I used the LockWorkStation() API defined on msdn, http://msdn.microsoft.com/en-us/library/aa376875%28VS.85%29.aspx I have included windows.h as told but still I am getting compilation error: .\source.cpp(5) : error C3861: 'LockWorkStation': identifier not found here is a sample code thats giving error. #include <Windows.h> int main() { LockWorkStation(); return 0; } Please tell me what I am missing here :( I am using MS-Visual studio 2005. Regards.

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  • Fixed footer with 960.gs

    - by Oguz
    I want to create fixed footer but , is it possible with 960 gs , because I am having trouble with height of container div . I can no set it to %100. <div class="container_12" > <div class="grid_3" id="side-space"></div> <div class="grid_6"> <div id="content-box"></div> </div> <div class="grid_3" id="side-space"></div> </div>

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  • Decorator pattern in C++

    - by AlgoMan
    Can someone give me an example of Decorator pattern in C++ ? I have come across the Java version of it. But C++ i have found it difficult to understand the examples that are given.

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  • Conditional Styling In Silverlight?

    - by DeanMc
    Hi, While I'm fine with standard control styling in silverlight I have recently began using more dynamic methods of fetching data to be displayed in items controls. One of the controls I am reworking is a collection of links. The issue I am having is that each link is coloured differently when moused over. One red, one blue, one green, etc. Is there a way to style these items without sacrificing the dynamics of using an items control with a data template?

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  • Minimum Hardware requirements for Android development

    - by vishwanath
    I need information about minimum hardware requirement I need to have better experience in developing Android application. My current configuration is as follows. P4 3.0 GHz, 512 MB of ram. Started with Hello Android development on my machine and experience was sluggish, was using Eclipse Helios for development. Emulator used to take lot of time to start. And running program too. Do I need to upgrade my machine for the development purpose or is there anything else I am missing on my machine(like heavy processing by some other application I might have installed). And If I do need to upgrade, do I need to upgrade my processor too(that counts to new machine actually, which I am not in favor of), or only upgrading RAM will suffice.

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  • Which should be created first ER Diagram OR Class Diagram?

    - by isthatacode
    The very first step i created a DFD. Then i moved on to create a Class Diagram. And while doing that i felt that i should create the ER diagram first. As there were many details which could not be captured in a Class diagram. So, my question should i create ERD first OR Class Diagrams ? your valuable inputs are appreciated guys!!! thanks for reading

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  • Bi-directional view model syncing with "live" collections and properties (MVVM)

    - by Schneider
    I am getting my knickers in a twist recently about View Models (VM). Just like this guy I have come to the conclusion that the collections I need to expose on my VM typically contain a different type to the collections exposed on my business objects. Hence there must be a bi-directional mapping or transformation between these two types. (Just to complicate things, on my project this data is "Live" such that as soon as you change a property it gets transmitted to other computers) I can just about cope with that concept, using a framework like Truss, although I suspect there will be a nasty surprise somewhere within. Not only must objects be transformed but a synchronization between these two collections is required. (Just to complicate things I can think of cases where the VM collection might be a subset or union of business object collections, not simply a 1:1 synchronization). I can see how to do a one-way "live" sync, using a replicating ObservableCollection or something like CLINQ. The problem then becomes: What is the best way to create/delete items? Bi-directinal sync does not seem to be on the cards - I have found no such examples, and the only class that supports anything remotely like that is the ListCollectionView. Would bi-directional sync even be a sensible way to add back into the business object collection? All the samples I have seen never seem to tackle anything this "complex". So my question is: How do you solve this? Is there some technique to update the model collections from the VM? What is the best general approach to this?

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  • Voting UI for showing like/dislike community comments side-by-side

    - by Justin Grant
    We want to add a comments/reviews feature to our website's plugin gallery, so users can vote up/down a particular plugin and leave an optional short comment about what they liked or didn't like about it. I'm looking for inspiration, ideally a good implementation elsewhere on the web which isn't annoying to end users, isn't impossibly complex to develop, and which enables users to see both good and bad comments side-by-side, like this: Like: 57 votes Dislike: 8 votes --------------------------------- -------------------------------- "great plugin, saved me hours..." "hard to install" "works well on MacOS and Ubuntu" "Broken on Windows Vista with UAC enabled" "integrates well with version 3.2" More... More... Anyone know a site which does something like this?

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  • Branchless memory manager?

    - by Richard Fabian
    Anyone thought about how to write a memory manager (in C++) that is completely branch free? I've written a pool, a stack, a queue, and a linked list (allocating from the pool), but I am wondering how plausible it is to write a branch free general memory manager. This is all to help make a really reusable framework for doing solid concurrent, in-order CPU, and cache friendly development. Edit: by branchless I mean without doing direct or indirect function calls, and without using ifs. I've been thinking that I can probably implement something that first changes the requested size to zero for false calls, but haven't really got much more than that. I feel that it's not impossible, but the other aspect of this exercise is then profiling it on said "unfriendly" processors to see if it's worth trying as hard as this to avoid branching.

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  • archiving strategies and limitations of data in a table

    - by Samuel
    Environment: Jboss, Mysql, JPA, Hibernate Our web application will be catering to a large amount of users (~ 1,000,000) and there are a lots of child table where user specific data are stored (e.g. personal, health, forum contributions ...). What would be the best practice to archive user & user specific information. [a] Would it be wise to move the archived user & user specific information to their respective tables within the same database (e.g. user_archive, user_forum_comments_archive ...) OR [b] Would you just mark the database entries with a flag in the original table(s) and just query only non archived entries. We have a unique constraint on User.loginid, how do you handle this requirement if the users are archived via 1-[a] (i.e if a user with loginid 'samuel' gets moved into the archive table and if a new user gets added with the same name in the original table, how would you prevent this. What would be the best strategy to address the unique key constraints. We have a requirement to selectively archive records and bring it back if necessary, will you rely on database tools are would you handle this via your persistence APIs exposed by the JPA entity model.

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  • What are some best practises and "rules of thumb" for creating database indexes?

    - by Ash
    I have an app, which cycles through a huge number of records in a database table and performs a number of SQL and .Net operations on records within that database (currently I am using Castle.ActiveRecord on PostgreSQL). I added some basic btree indexes on a couple of the feilds, and as you would expect, the peformance of the SQL operations increased substantially. Wanting to make the most of dbms performance I want to make some better educated choices about what I should index on all my projects. I understand that there is a detrement to performance when doing inserts (as the database needs to update the index, as well as the data), but what suggestions and best practices should I consider with creating database indexes? How do I best select the feilds/combination of fields for a set of database indexes (rules of thumb)? Also, how do I best select which index to use as a clustered index? And when it comes to the access method, under what conditions should I use a btree over a hash or a gist or a gin (what are they anyway?).

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  • Separating weakly linked database schemas

    - by jldugger
    I've been tasked with revisiting a database schema we designed and use internally for various ticketing and reporting systems. Currently there exists about 40 tables in one Oracle database schema supporting perhaps six webapps. However, there's one unifying relationship amongst them all: a rooms table describing the room. Room name, purpose and other data are thrown into a shared table for each app. My initial idea was to pull each of these applications into a separate database, and perform joins between a given database and the room database. But I've discovered this solution prevents foreign key constraints in SQL Server 2005. It seems silly to duplicate one table for each app and keep those multiple copies synchronized. Should I just leave everything in one large DB, or is there something else I can do separate the tables without losing FK constraints?

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  • What resources will help me understand the fundamentals of Relational Database Systems.

    - by Rachel
    This are few of the fundamental database questions which has always given me trouble. I have tried using google and wiki but I somehow I miss out on understanding the functionality rather than terminology. If possible would really appreciate if someone can share more insights on this questions using some visual representative examples. What is a key? A candidate key? A primary key? An alternate key? A foreign key? What is an index and how does it help your database? What are the data types available and when to use which ones?

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  • is there evidence that offshoring is causing developer salaries to go down? [closed]

    - by jcollum
    I realize this is a controversial and political topic. I'm trying to decide if offshoring is something that is effecting our industry in any substantial way or if it's just some bugaboo. I've read various posts on SO about it, but none addressed the idea of evidence for offshoring. Studies, papers, opinions of people who know about such things etc. I hear a lot about offshoring and its effect on our job market. However it all seems to be hearsay and conjecture. It does seem like some people are genuinely worried about it. This offshoring thing has been going on for quite some time, should be enough time for some real data to come out. If I had to pick a number I'd say it started during the dotcom boom -- a time when the need for developers far outweighed the local talent pool. We're now in a time when the talent pool is expensive and corporate wallets are tight, seems like an ideal time to find a good cheap developer in some other country. But is that actually happening? From reading some posts here on SO, I've concluded that offshoring is a really tough thing to do right. There are a lot of companies who think (or say) they can do it right, but some small percentage of them are actually able to pull it off. Is offshoring affecting the job market in any measurable way? Is offshoring measurable at all? Do we need to stop worrying about this?

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  • What tool can I use to test my web app in different resolutions?

    - by strakastroukas
    Back in the past, i found a third party webpage that was able to capture and save images of my website in different resolutions and browsers. Of course i have no more that bookmark... So is there any webpage or application where i can see how my webpage looks like in different resolution? And here are the resolutions i would like to check for... 1. 1024x768 24.56% 2. 1280x800 22.06% 3. 1280x1024 13.42% 4. 1366x768 7.10% 5. 1440x900 6.68%

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  • How to pass data to another droid device when the other device isn't expecting it

    - by James Black
    I am working on an application and one feature that would make it really useful is the ability to share some information, but the other device may not be expecting the data to be sent. For example, if I am reading a really good book, and I realize that a friend may like it, I could use an application to send the data to him, so he could order the book from Amazon. But, since he isn't expecting the data, I would hate for the application to be polling a server every so often, as that will be needlessly draining the battery. Ideally it would be great if there was a way to make a phone call to the target device, send a data packet and end the call. If it could be done and prevent the phone from ringing, then it would be very useful to me. I am curious if there is some way to send data between devices without polling.

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