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  • Database design: circular references

    - by SlappyTheFish
    I have three database tables: users emails invitations Emails are linked to users by a user_id field. Invitations are also linked to users by a user_id field Emails can be created without an invitation, but every invitation must have an email. I would like to link the emails and invitations tables so it is possible to find the email for a particular invitation. However this creates a circular reference, both an invitation and an email record hold the id for the same user. Is this bad design and if so, how could I improve it? My feeling is that with use of foreign keys and good business logic, it is fine.

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  • 'Design By Contract' in C#

    - by IAmCodeMonkey
    I wanted to try a little design by contract in my latest C# application and wanted to have syntax akin to: public string Foo() { set { Assert.IsNotNull(value); Assert.IsTrue(value.Contains("bar")); _foo = value; } } I know I can get static methods like this from a unit test framework, but I wanted to know if something like this was already built-in to the language or if there was already some kind of framework floating around. I can write my own Assert functions, just don't want to reinvent the wheel.

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  • Java Design Questions - Class, Function, Access Modifiers

    - by Ron
    I am newbie to Java. I have some design questions. Say I have a crawler application, that does the following: 1. Crawls a url and gets its content 2. Parses the contents 3. Displays the contents How do you decide between implementing a function or a class? -- Should the parser be a function of the crawler class, or should it be a class in itself, so it can be used by other applications as well? -- If it should be a class, should it be protected or public class? How do you decide between implementing a public or protected class? -- If I had to create a class to generate stats from the parsed contents for eg, should that class be protected (so only the crawler class can access it) or should it be public? Thanks Ron

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  • Optimized way to convert table base to table less design

    - 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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  • database design in google app engine

    - by iamgopal
    hi , i am designing a simple project based to do list. the idea is to define tasks under project ( no workflow - just "task is completed" or not is required. ) in a hirarchial way. i.e. each task has multiple task and that task may have other multiple task. a project can be said to be completed if all task under that project are completed. , i tought of using refrenceproeperty to create hirarchy , but could not figure out easy way ( which do not take more than 30 seconds to find all the children of a project and check weather it is completed or not ) . to detect if project is complete or not. how to design database for such job ? and also , if i need to copy the project in order to define another project , how to copy hierarchical data ?

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  • Database with users design

    - by 1110
    I am in database design development phase. Application will work with large number of users (LARGE :)) I designed 80% of database but I have one Users table which is connected to everything else: Users {UserId, FirstName, LastName, Username, Password, PasswordQuestion, PasswordAnswer, Gender, RoleId, LastLoginDate etc etc} I saw asp.net membership database structure where Users and Membership are two tables. My questions are: Should I use one users table with all users data in it or more tables? If answer is 'more tables', what tables to use? Any advice on how to structure relation between those tables? This is sample relation that I have, and trying to improve. I don't understand why user and userChild are separated tables?

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  • Best Design pattern for social media file transfer

    - by Onema
    Our system would like our clients to link their accounts with different social media sites like youtube, vimeo, facebook, myspace and so on. One of the benefits we would like to give to the user is to transfer, update and delete files they have uploaded to our sites and transfer them to the social media sites mentioned above. this files could be videos, images or audio. We started thinking about using a strategy pattern, as all of these sites share a common process ( authentication, connection, use the API to transfer/edit/delete the file ), but we soon realized that it may not work as me may want to use some of the extended functionality that is specific to each service (eg: associate a youtube video with a channel, or upload images to a specific album on facebook, and much, much more...) My question is, what would be the best Structural Design Patter to use for this scenario?

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  • Java: design problem with final-value and empty constructor

    - by HH
    $ javac InitInt.java InitInt.java:7: variable right might not have been initialized InitInt(){} ^ 1 error $ cat InitInt.java import java.util.*; import java.io.*; public class InitInt { private final int right; // Design Problem? // I feel the initialization problem is just due to bad style. InitInt(){} InitInt{ // Still the error, "may not be initialized" // How to initialise it? if(snippetBuilder.length()>(charwisePos+25)){ right=charwisePos+25; }else{ right=snippetBuilder.length()-1; } } public static void main(String[] args) { InitInt test = new InitInt(); System.out.println(test.getRight()); } public int getRight(){return right;} } Partial Solutions and Suggestions use "this" to access methods in the class, instead of creating empty constructor change final to non-final with final field value: initialize all final values in every constructor remove the empty constructor, keep your code simple and clean

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  • Django view function design

    - by dragoon
    Hi, I have the view function in django that written like a dispatcher calling other functions depending on the variable in request.GET, like this: action = '' for act in ('view1', 'view2', 'view3', 'view4', ... ): if act in request.GET: action = act break ... if action == '': response = view0(request, ...) elif action == 'view1': response = view1(request, ...) elif action == 'view2': response = view2(request, ...) ... The global dispatcher function contains many variable initialization routines and these variables are then used in viewXX functions. So I feed that this is bad view design but I don't know how I can rewrite it?

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  • Video learning for database design

    - by donpal
    I'm trying to learn good relational database design (using mysql and php if that makes any difference). I've already done some database work, so I'm not totally clueless, but I suspect that my solutions may not have adhered to best practices for efficient searching, optimization, etc. Can someone suggest a good set of videos on the topic? If you know something is superb or has really made a difference in your own learning, please post your suggestion. Prefer videos, but books (as long as they're not too huge) are ok too. But prefer videos. Thank you

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  • Exception design: Custom exceptions reading data from file?

    - by User
    I have a method that reads data from a comma separated text file and constructs a list of entity objects, let's say customers. So it reads for example, Name Age Weight Then I take these data objects and pass them to a business layer that saves them to a database. Now the data in this file might be invalid, so I'm trying to figure out the best error handling design. For example, the text file might have character data in the Age field. Now my question is, should I throw an exception such as InvalidAgeException from the method reading the file data? And suppose there is length restriction on the Name field, so if the length is greater than max characters do I throw a NameTooLongException or just an InvalidNameException, or do I just accept it and wait until the business layer gets a hold of it and throw exceptions from there? (If you can point me to a good resource that would be good too)

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  • C# ProgressBar design pattern

    - by MadSeb
    Hi, I'm working on a database upgrader application. The upgrader updates the schema of a database ( adds new columns, renames columns , adds new tables, new views to an existing database by executing SQL statements ). When a user wants to upgrade from version 1.0 to 2.0 , "Upgrader" objects are taken from an object factory and the "Execute" method of each "Upgrader" is called. The GUI of the application has a progress bar and each time an upgrader object performs a SQL statement the progress bar gets incremented. while (!version.Equal(CurrentVersion)) { IUpgrader myUpgrader = UpgraderFactory.GetUpgrader(version); myUpgrader.Execute(UpgradedFile,progressbar); version.Increment(); } My question is very simple : how should the upgrader object communicate with the progressbar. In the code above, the upgrader object is given direct access to the progressbar but I'm wondering if some better way of doing this or better design pattern exists. Regards, Seb

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  • Is OO design's strength in semantics or encapsulation?

    - by Phil H
    Object-oriented design (OOD) combines data and its methods. This, as far as I can see, achieves two great things: it provides encapsulation (so I don't care what data there is, only how I get values I want) and semantics (it relates the data together with names, and its methods consistently use the data as originally intended). So where does OOD's strength lie? In constrast, functional programming attributes the richness to the verbs rather than the nouns, and so both encapsulation and semantics are provided by the methods rather than the data structures. I work with a system that is on the functional end of the spectrum, and continually long for the semantics and encapsulation of OO. But I can see that OO's encapsulation can be a barrier to flexible extension of an object. So at the moment, I can see the semantics as a greater strength. Or is encapsulation the key to all worthwhile code?

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  • Design view not working in Web Projects in Visual Studio 2008

    - by HenryHey
    When I try to edit an ASPX file with the Design View it freezes for a moment and does nothing, not even an error message. Looking through menus I've seen some strange things: If I go to Tools-Options-HTML Designer it gives me no options on the right panel, just a "Error loading property page" message. When I try to open a file using "Open With..." there should be something like "Web Form - Editor", but it is missing and I can only open them using Code View. I've tried repairing Visual Studio and reinstalling WebDesignerCore, but nothing works. Anyone had the same problem?

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  • Design - Where should objects be registered when using Windsor

    - by Fredrik Jansson
    I will have the following components in my application DataAccess DataAccess.Test Business Business.Test Application I was hoping to use Castle Windsor as IoC to glue the layers together but I am bit uncertain about the design of the gluing. My question is who should be responsible for registering the objects into Windsor? I have a couple of ideas; Each layer can register its own objects. To test the BL, the test bench could register mock classes for the DAL. Each layer can register the object of its dependencies, e.g. the business layer registers the components of the data access layer. To test the BL, the test bench would have to unload the "real" DAL object and register the mock objects. The application (or test app) registers all objects of the dependencies. Can someone help me with some ideas and pros/cons with the different paths? Links to example projects utilizing Castle Windsor in this way would be very helpful.

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  • What are some good design patterns for CRUD?

    - by Extrakun
    I am working with a number of data entities which can be created, read, updated and deleted, and I find myself writing more or less the same code for them. For example, I need to sometimes output data as JSON, and sometimes in a table format. I am finding myself writing 2 different types of view to export the data to. Also, the creation of those entities within DB usually differs just by the SQL statements and the input parameters. I am thinking of creating a strategy pattern to represent different 'contexts'. For example, the read() method of an AJAX context will be to return the data as JSON. However, I wonder if others have deal with this problem beforehand and will like to know what design patterns are usually use for CRUD operations.

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  • Which design pattern to manage windows?

    - by Lu Lu
    Hello, I am using .NET 2.0 & C# to develop a WinForm Mdi application. It will have a Main Window and a lot of mdi windows. I am thinking I should use which design pattern to manage mdi windows. Because I want only one instance for each window, if window is existed, I will show it on top, & otherwise I will create and show it. Note: a mdi window is opened from Menus of Main Window or open from another mdi window. An example is very good. Update: Menu's status is depended on mdi window's status. Ex: If Window 'A' is openned - menu 'A' - disabled. When window 'A' is closed - I update menu 'A' status to Enabled. Thanks.

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  • Modeling software for network serialization protocol design

    - by Aurélien Vallée
    Hello, I am currently designing a low level network serialization protocol (in fact, a refinement of an existing protocol). As the work progress, pen and paper documents start to show their limits: i have tons of papers, new and outdated merged together, etc... And i can't show anything to anyone since i describe the protocol using my own notation (a mix of flow chart & C structures). I need a software that would help me to design a network protocol. I should be able to create structures, fields, their sizes, their layout, etc... and the software would generate some nice UMLish diagrams.

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  • ERD-CLASS design

    - by Mahesh
    Hello guyz,i am new to daatbase and class diagram.I just get scenarios from internet and try to develop ERD and Class Diagram for them.But the following scenario has caused me some problems, and i am not sure about my design. "Whenever an employee fills leave application form, the leave application should be appeared for approval to his/her team leader. Team Leader has the option to change the date of requested leave and to approve or reject the leave. Employee also has the option to change date of previously unapproved leaves or to cancel any of unapproved leave. In case of team leader, he can approve his own leaves. Management should be able to create categories of leaves like (Casual, Sick, Planned work, etc) and should be able to adjust the days allocated to each type of leave". I have identified these as entities for ERD 1) Employee(I think i dont need to make entity for Technical lead,since he is an employee) 2) LeaveHistory 3) LeaveCategory Plz correct me if the system need more classes or entities

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  • Adding controls dynamically at design time vb.net

    - by chris
    I have been developing some custom smart tags. I am using a DesignerActionMethodItem which gets me to a fired method in code. When I try to hit the controls.Add the control is added but it seems the designer is unaware of it. It is never serialized and it goes away when the form is refreshed in the designer. Any help would be greatly appreciated. I am sort of stuck and google hasn't helped me. Please don't send me anything about smart tags that has nothing to do with adding controls dynamically at design time, I have already read so many looking for this.

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  • Design for tagging system in GAE-J

    - by tempy
    I need a simple tagging system in GAE-J. As I see it, the entity that is being tagged should have a collection of keys referring to the tags with which it's associated. A tag entity should simply contain the tag string itself, and a collection of keys pointing to the entities associated with the tag. When an entity's list of tags is altered, the system will create a new tag if the tag is unknown, and then append the entity's key to that tag's key collection. If the tag already exists, then the entity's key is simply appended to the tag's key collection. This seems relatively straight-forward and uncontroversial to me, but I would like some feedback on this design, just to be sure.

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  • Which design pattern should I be using?

    - by Gabriel
    Here's briefly what I'm trying to do. The user supplies me with a link to a photo from one of several photo-sharing websites (such as Flickr, Zooomr, et. al). I then do some processing on the photo using their respective APIs. Right now, I'm only implementing one service, but I will most likely add more in the near future. I don't want to have a bunch of if/else or switch statements to define the logic for the different websites (but maybe that's necessary?) I'd rather just call GetImage(url) and have it get me the image from whatever service the url's domain is from. I'm confused how the GetImage function and classes should be designed. Maybe I need the strategy pattern? I'm still reading and trying to understand the various design patterns and how I could make one fit in this case. I'm doing this in C#, but this question is language-agnostic.

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  • database design suggesion

    - by Bharanikumar
    Hi , am going to start new travel site, I want some advise from guru's regarding database design , Things coming to picture are, Book taxi online , This is the core idea, So i like to implement lot of jquery,ajax stuff in my site , Main thing site must run veryt fast,safe,security, In mysql , which typw shall i use, MYISAM OR INNODB Which is best type for ajax works, fast,safe ,secure ,performance view . This is my demo site, Just look this site, i implemented some ajax stuff here, my-url In this site please choose the postcode in the taxifrom tab, It ask you value please enter, just enter nw7 , See How long it will take for response,some time no response and system goes to hang or idle mode, Also please look the diversion , select No diversion, There you will list of textbox, enter the nw3 then hit the search icon , See after 80seconds only , you will get response from DB, See this too bad response ... This is DB , my Database type if myisam ,no idexing , no fulltext and nothing...no constraints, So please advise me , which database type i choose, Myisam or innodb, Thanks Bharanikumar

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  • Dynamic table design (common lookup table), need a nice query to get the values

    - by Swoosh
    sql2005 This is my simplified example: (in reality there are 40+ tables in here, I only showed 2) I got a table called tb_modules, with 3 columns (id, description, tablename as varchar): 1, UserType, tb_usertype 2, Religion, tb_religion (Last column is actually the name of a different table) I got an other table that looks like this: tb_value (columns:id, tb_modules_ID, usertype_OR_religion_ID) values: 1111, 1, 45 1112, 1, 55 1113, 2, 123 1114, 2, 234 so, I mean 45, 55, 123, 234 are usertype OR religion ID's (45, 55 usertype, 123, 234 religion ID`s) Don't judge, I didn't design the database Question How can I make a select, showing * from tb_value, plus one column That one column would be TITLE from the tb_usertype or RELIGIONNAME from the tb_religion table I would like to make a general thing. Was thinking initially about maybe a SQL function that returns a string, but I think I would need dynamic SQL, which is not ok in a function. Anyone a better idea ?

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  • amazon design doubt

    - by praveen
    I was looking at the amazon website and was wondering how one of the feature would have been implemented. The feature : what customers buy after viewing a particular item. If i were to develop such a feature i would probably generate a session id for each user session and store the session id-page id combination in a log file. and if a book is bought set a separate flag for the session id-page id. A separate program can then be run on the log file periodically, to identify the groups that were bought together/viewed together and that information can be stored in a persistent file. This is ofcourse a simple solution without taking into consideration the distributed nature of the servers - but would this suffice or can you help me identify a better design.

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