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  • Facebook Privacy Permissions Design

    - by Ian
    Does anyone know the general layout of how facebook's privacy permissions system works (database)? I've been trying to figure out how they manage to have such a complex set of rules be applied to various content on their site, yet it remains fast. How are they doing that?

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  • Right design to validate attributes of a class instance

    - by systempuntoout
    Having a simple Python class like this: class Spam(object): __init__(self, description, value): self.description = description self.value = value Which is the correct approach to check these constraints: "description cannot be empty" "value must be greater than zero" Should i: 1.validate data before creating spam object ? 2.check data on __init__ method ? 3.create an is_valid method on Spam class and call it with spam.isValid() ? 4.create an is_valid static method on Spam class and call it with Spam.isValid(description, value) ? 5.check data on setters? 6.... Could you recommend a well designed\Pythonic\not verbose (on class with many attributes)\elegant approach?

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  • C++ design with static methods

    - by user231536
    I would like to define as class X with a static method: class X { static string get_type () {return "X";} //other virtual methods } I would like to force classes which inherit from X to redefine the get_type() method and return strings different from "X" (I am happy if they just redefine get_type for now). How do I do this? I know that I cannot have virtual static methods. Edit: The question is not about the type_id, but in general about a static method that should be overriden. For example class X { static int getid() {return 1;} }

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  • Needs opinions based on design guidelines .

    - by Abu Hamzah
    i am in the process of desigining my domain model and i know its very hard to suggest without knowledge of domain but what i am asking is how to implement or the best way of implementing the baseclass in my domain model. here are few classes: PartialPerson.cs Facilities.cs Visit.cs EntryPoint.cs etc.... my baseclass looks like this: public abstract class BaseClass { public int InfoId { get; } public int PersonId { get; } } here is what i am confused and need help. how do i implement the above baseclass? in the PartialPerson,Facilities,Visit...

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  • Mysql search design

    - by neil
    I'm designing a mysql database, and i'd like some input on an efficient way to store blog/article data for searching. Right now, I've made a separate column that stores the content to be searched - no duplicate words, no words shorter than four letters, and no words that are too common. So, essentially, it's a list of keywords from the original article. Also searched would be a list of tags, and the title field. I'm not quite sure how mysql indexes fulltext columns, so would storing the data like that be ineffective, or redundant somehow? A lot of the articles are on the same topic, so would the score be hurt by so many of the rows having similar keywords? Also, for this project, solutions like sphinx, lucene or google custom seach can't be used -- only php & mysql. Thanks!

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  • Design pattern suggestion

    - by Avinash
    Following is the problem statement. There are n numbers of match strings, If event A occurs and then in certain period of time event B occurs then I do not raise alarm. but if B do not occurs then i have to raise alarm. There can be multiple chain of events which defines whether to raise alarm or not.

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  • design decision between array or object save in database

    - by justjoe
    i code some configuration setting. And need those values to be load, everytime my webapp start. yes, it's somekind autoload setting. But, right now, i have to choose between save it as object or array. is there any different between them when we save them in database ? which one is faster or maintainable or other pro and cons thanks

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  • Database design -- does it respect 3rd NF?

    - by Flavius
    Hi I have the following relations (tables) in a relational model Person person_id, first_name, last_name, address Student person_id, matr_nr Teacher person_id, salary Lecture lecture_id, lect_name, lect_description Attendees lecture_id, person_id, date I'm wondering about the functional dependencies of Student and Teacher. Do these tables respect the 3rd normal form? Which should be the primary keys of these tables?

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  • Design pattern: Polymorphism for list of objects

    - by ziang
    Suppose I have a class A, and A1, A2 inherits from A. There are 2 functions: List<A1> getListA1(){...} List<A2> getListA2(){...} Now I want to do something similar to both A1 and A2 in another function public void process(List<A>){...} If I want to pass the instance of either ListA1 or ListA2, of course the types doesn't match because the compiler doesn't allow the coercion from List< A1 to List< A. I can't do something like this: List<A1> listA1 = getListA1(); List<A> newList = (List<A>)listA1; //this is not allowed. So what is the best approach to the process()? Is there any way to do it in a universal way rather than write the similar code to both List and List?

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  • Design best practice - best way to handle user selection

    - by user1457227
    I'm an experienced developer (WPF) moving over to Android development. My question: an app I am developing allows the user to browse their local storage (such as SDCARD) and select a file. Now, should I simply create a new Activity (after the user has made a selection) to handle what I want to have the app do with that chosen file, -or- is the better approach to pass the path/name of the selected file back to the main Activity and let IT launch the next Activity? In other words, is the better practice to have the main Activity launch other (support) activities, or is it perfectly ok and normal to have one activity chain to another and on and on? Thanks!

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  • Best Design Pattern to Implement while Mapping Actions in MVC

    - by FidEliO
    What could be the best practices of writing the following case: We have a controller which based on what paths users take, take different actions. For example: if user chooses the path /path1/hello it will say hello. If a user chooses /path1/bye?name="Philipp" it will invoke sayGoodBye() and etc. I have written a switch statement inside the controller which is simple, however IMO not efficient. What are the best way to implement this, considering that paths are generally String. private void takeAction() { switch (path[1]) { case "hello": //sayHello(); break; case "bye": //sayBye(); break; case "case3": //Blah(); break; ... } }

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  • Which design pattern fits - strategy makes sense ?

    - by user554833
    --Bump *One desperate try to get someone's attention I have a simple database table that stores list of users who have subscribed to folders either by email OR to show up on the site (only on the web UI). In the storage table this is controlled by a number(1 - show on site 2- by email). When I am showing in UI I need to show a checkbox next to each of folders for which the user has subscribed (both email & on site). There is a separate table which stores a set of default subscriptions which would apply to each user if user has not expressed his subscription. This is basically a folder ID and a virtual group name. But, Email subscriptions do not count for applying these default groups. So if no "on site" subscription apply default group. Thats the rule. How about a strategy pattern here (Pseudo code) Interface ISubscription public ArrayList GetSubscriptionData(Pass query object) Public class SubscriptionWithDefaultGroup Implement ArrayList GetSubscriptionData(Pass query object) Public class SubscriptionWithoutDefaultGroup Implement ArrayList GetSubscriptionData(Pass query object) Public class SubscriptionOnlyDefaultGroup Implement ArrayList GetSubscriptionData(Pass query object) does this even make sense? I would be more than glad for receive any criticism / help / notes. I am learning. Cheers

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  • Database design: one huge table or separate tables?

    - by littlegreen
    Currently I am designing a database for use in our company. We are using SQL Server 2008. The database will hold data gathered from several customers. The goal of the database is to acquire aggregate benchmark numbers over several customers. Recently, I have become worried with the fact that one table in particular will be getting very big. Each customer has approximately 20.000.000 rows of data, and there will soon be 30 customers in the database (if not more). A lot of queries will be done on this table. I am already noticing performance issues and users being temporarily locked out. My question, will we be able to handle this table in the future, or is it better to split this table up into smaller tables for each customer?

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  • Decorator Design Pattern Use With Service Objects (wSingleton)

    - by Dustin
    I'm working on a project where I need to add some functionality to a service object and using a decorator to add it in seems like a good fit. However, I've only ever used decorators with simple beans, never on a singleton like a service object. Has anyone ever done this before and what are the pros and cons? In this case I don't think creating a subclass will work so a decorator seems to be a good fit. What are your thoughts on doing this?

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  • basic database design table on rails

    - by runcode
    I am confuse on a concept. I am doing this on rails. Is that Entity set equal to a table in the database? Is that Relationship set equal to a table in the database? Let say we have Entity set "USER" and Entity set "POST" and Entity set "COMMENT" User- can post many posts and comments as they want Post- belong to users Comments-belong to posts ,users, so comment is weak entity. SCHEMA ====== USER -id -name POST -id -user_id(FK) -comment_id (FK) COMMENT -id -user_id (FK) -post_id (FK) so USER,POST,COMMENT are tables I think. And what else is a table? And do I need a table for the relationship??

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  • Policies Array Class-Design wrapper

    - by PT
    Hi, i want to write an wrapper for different Array Classes with different Policies. For example: typedef ArrayType<useValArray,StdAllocator> Array; // one global assignment I want to use the class like a blitz++ Array for example: Array<double,2> x(2,2); //maps the Array to an Valarray or to a Blitz++ Array Array<double,2> x2(5,6); is this Posible? Which technics i need to realise that?

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  • Database design to hold multiple iteration measurements

    - by Valder
    Hi All. I am new to sqlite and SQL in general. I am keen to switch from flat-files to sqlite for holding some measurement information. I need a tip on how to better layout the database, since I have zero experience with this. I have a ~10000 unique statistic counters that are collected before and after each test iteration. Max number of iterations are 10, though it could be less. I was thinking the following: CREATE TABLE stat_names(stat_id, stat_name); CREATE TABLE stats_per_iteration(stat_id, before_iter_1, after_iter_1, before_iter_2, after_iter_2, ...); stat_names table would hold mapping of a full counter to a uniq stat_id. stats_per_iteration table would hold mesurement data 1 + 10 * 2 columns. stat_names.stat_id = stats_per_iteration.stat_id OR maybe I should have a separate table for each iteration? Which would results in 1 + 10 tables in database. Thanks!

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  • UI Design - design pattern for city/country drop down? (ASP.NET MVC)

    - by JK
    What is the best way to do a city/country dropdown pair in ASP.NET MVC? I see lots of places with country above city, but that's unnatural: in real life we write city/country. I've used city, then country, but the problem is that the user then has to go backwards after changing the country. The other problem is what do you do about cities/countries not in your list? If city/country are both drop downs, then the user cant type their own city if it is missing. But if you have a dropdown and a textbox, that makes it unwieldy (you end up with 4 controls to enter 2 pieces of data). Are there any examples websites where the city/country dropdown pair are done in a very useable and clear manner?

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  • sports league database design

    - by John
    Hello, I'm developing a database to store statistics for a sports league. I'd like to show several tables: - league table that indicates the position of the team in the current and previous fixture - table that shows the position of a team in every fixture in the championship I have a matches table: Matches (IdMatch, IdTeam1, IdTeam2, GoalsTeam1, GoalsTeam2) Whith this table I can calculate the total points of every team based on the matches the team played. But every time I want to show the league table I have to calculate the points. Also I have a problem to calculate in which position classified a team in the last 10 fixtures cause I have to make 10 queries. To store the league table for every fixture in a database table is another approach, but every time I change a match already played I have to recalculate every fixture from there... Is there a better approach for this problem? Thanks

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  • database design help for game / user levels / progress

    - by sprugman
    Sorry this got long and all prose-y. I'm creating my first truly gamified web app and could use some help thinking about how to structure the data. The Set-up Users need to accomplish tasks in each of several categories before they can move up a level. I've got my Users, Tasks, and Categories tables, and a UserTasks table which joins the three. ("User 3 has added Task 42 in Category 8. Now they've completed it.") That's all fine and working wonderfully. The Challenge I'm not sure of the best way to track the progress in the individual categories toward each level. The "business" rules are: You have to achieve a certain number of points in each category to move up. If you get the number of points needed in Cat 8, but still have other work to do to complete the level, any new Cat 8 points count toward your overall score, but don't "roll over" into the next level. The number of Categories is small (five currently) and unlikely to change often, but by no means absolutely fixed. The number of points needed to level-up will vary per level, probably by a formula, or perhaps a lookup table. So the challenge is to track each user's progress toward the next level in each category. I've thought of a few potential approaches: Possible Solutions Add a column to the users table for each category and reset them all to zero each time a user levels-up. Have a separate UserProgress table with a row for each category for each user and the number of points they have. (Basically a Many-to-Many version of #1.) Add a userLevel column to the UserTasks table and use that to derive their progress with some kind of SUM statement. Their current level will be a simple int in the User table. Pros & Cons (1) seems like by far the most straightforward, but it's also the least flexible. Perhaps I could use a naming convention based on the category ids to help overcome some of that. (With code like "select cats; for each cat, get the value from Users.progress_{cat.id}.") It's also the one where I lose the most data -- I won't know which points counted toward leveling up. I don't have a need in mind for that, so maybe I don't care about that. (2) seems complicated: every time I add or subtract a user or a category, I have to maintain the other table. I foresee synchronization challenges. (3) Is somewhere in between -- cleaner than #2, but less intuitive than #1. In order to find out where a user is, I'd have mildly complex SQL like: SELECT categoryId, SUM(points) from UserTasks WHERE userId={user.id} & countsTowardLevel={user.level} groupBy categoryId Hmm... that doesn't seem so bad. I think I'm talking myself into #3 here, but would love any input, advice or other ideas.

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  • Help Desk Database Design

    - by user237244
    The company I work at has very specific and unique needs for a help desk system, so none of the open source systems will work for us. That being the case, I created a custom system using PHP and MySQL. It's far from perfect, but it's infinitely better than the last system they were using; trust me! It meets most of our needs quite nicely, but I have a question about the way I have the database set up. Here are the main tables: ClosedTickets ClosedTicketSolutions Locations OpenTickets OpenTicketSolutions Statuses Technicians When a user submits a help request, it goes in the "OpenTickets" table. As the technicians work on the problem, they submit entries with a description of what they've done. These entries go in the "OpenTicketSolutions" table. When the problem has been resolved, the last technician to work on the problem closes the ticket and it gets moved to the "ClosedTickets" table. All of the solution entries get moved to the "ClosedTicketSolutions" table as well. The other tables (Locations, Statuses, and Technicians) exist as a means of normalization (each location, status, and technician has an ID which is referenced). The problem I'm having now is this: When I want to view a list of all the open tickets, the SQL statement is somewhat complicated because I have to left join the "Locations", "Statuses", and "Technicians" tables. Fields from various tables need to be searchable as well. Check out how complicated the SQL statement is to search closed tickets for tickets submitted by anybody with a first name containing "John": SELECT ClosedTickets.*, date_format(ClosedTickets.EntryDate, '%c/%e/%y %l:%i %p') AS Formatted_Date, date_format(ClosedDate, '%c/%e/%y %l:%i %p') AS Formatted_ClosedDate, Concat(Technicians.LastName, ', ', Technicians.FirstName) AS TechFullName, Locations.LocationName, date_format(ClosedTicketSolutions.EntryDate, '%c/%e/%y') AS Formatted_Solution_EntryDate, ClosedTicketSolutions.HoursSpent AS SolutionHoursSpent, ClosedTicketSolutions.Tech_ID AS SolutionTech_ID, ClosedTicketSolutions.EntryText FROM ClosedTickets LEFT JOIN Technicians ON ClosedTickets.Tech_ID = Technicians.Tech_ID LEFT JOIN Locations ON ClosedTickets.Location_ID = Locations.Location_ID LEFT JOIN ClosedTicketSolutions ON ClosedTickets.TicketNum = ClosedTicketSolutions.TicketNum WHERE (ClosedTickets.FirstName LIKE '%John%') ORDER BY ClosedDate Desc, ClosedTicketSolutions.EntryDate, ClosedTicketSolutions.Entry_ID One thing that I'm not able to do right now is search both open and closed tickets at the same time. I don't think a union would work in my case. So I'm wondering if I should store the open and closed tickets in the same table and just have a field indicating whether or not the ticket is closed. The only problem I can forsee is that we have so many closed tickets already (nearly 30,000) so the whole system might perform slowly. Would it be a bad idea to combine the open and closed tickets?

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  • What Design Pattern To Replace 'CurrentStep' Variable

    - by Rob P.
    Tried to search but didn't know how to phrase it. I've got some code that is essentially... Private CurMajorStep as Integer = 0 Private CurMinorStep as Integer = 0 Public Sub PerformNextStep() Select Case iMajorStep Case 0 ThingOne() Case 1 ThingTwo() Case 2 ThingThree() Case 3 ThingFour() Case 4 AnythingElse() Case 5 Finish() End Select End Sub And then, in some of those, the CurMinorStep keeps track of the current state of that particular 'step'. I hope that all makes sense. The code is messy and I know it's going to be problematic to maintain. Can someone point me to a clean OO pattern to handle this?

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