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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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• Data access layer design

  - by Sam

  I have a web app and a console application accessing a db. The db has 2 tables (A, B) one of which (A) is specific to the web app. When writing a data access layer, what is the best way to do it? Technically data access layer should provide access to all the data accessible. In doing so, methods to interact with A are exposed to the console application if we have single access layer. Does creating 2 access layers to 2 table in the same database makes any sense? What is a good way to do it?

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• C++: How to design a utility class?

  - by Martijn Courteaux

  Hi, The title says it all. But I don't know if I should go for static methods, just a header, a class, or something else? What would be best practice? But, I don't want to have an instance of a utility class. I want to add functions like: Uint32 MapRGB (int r, int g, int b); const char* CopyString(const char* char); // etc. You know: utility methods...

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• Database Design Question

  - by Soo

  Ok SO, I have a user table and want to define groups of users together. The best solution I have for this is to create three database tables as follows: UserTable user_id user_name UserGroupLink group_id member_id GroupInfo group_id group_name This method keeps the member and group information separate. This is just my way of thinking. Is there a better way to do this? Also, what is a good naming convention for tables that link two other tables?

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• What are the disadvantages of self-encapsulation?

  - by Dave Jarvis

  Background Tony Hoare's billion dollar mistake was the invention of null. Subsequently, a lot of code has become riddled with null pointer exceptions (segfaults) when software developers try to use (dereference) uninitialized variables. In 1989, Wirfs-Brock and Wikerson wrote: Direct references to variables severely limit the ability of programmers to re?ne existing classes. The programming conventions described here structure the use of variables to promote reusable designs. We encourage users of all object-oriented languages to follow these conventions. Additionally, we strongly urge designers of object-oriented languages to consider the effects of unrestricted variable references on reusability. Problem A lot of software, especially in Java, but likely in C# and C++, often uses the following pattern: public class SomeClass { private String someAttribute; public SomeClass() { this.someAttribute = "Some Value"; } public void someMethod() { if( this.someAttribute.equals( "Some Value" ) ) { // do something... } } public void setAttribute( String s ) { this.someAttribute = s; } public String getAttribute() { return this.someAttribute; } } Sometimes a band-aid solution is used by checking for null throughout the code base: public void someMethod() { assert this.someAttribute != null; if( this.someAttribute.equals( "Some Value" ) ) { // do something... } } public void anotherMethod() { assert this.someAttribute != null; if( this.someAttribute.equals( "Some Default Value" ) ) { // do something... } } The band-aid does not always avoid the null pointer problem: a race condition exists. The race condition is mitigated using: public void anotherMethod() { String someAttribute = this.someAttribute; assert someAttribute != null; if( someAttribute.equals( "Some Default Value" ) ) { // do something... } } Yet that requires two statements (assignment to local copy and check for null) every time a class-scoped variable is used to ensure it is valid. Self-Encapsulation Ken Auer's Reusability Through Self-Encapsulation (Pattern Languages of Program Design, Addison Wesley, New York, pp. 505-516, 1994) advocated self-encapsulation combined with lazy initialization. The result, in Java, would resemble: public class SomeClass { private String someAttribute; public SomeClass() { setAttribute( "Some Value" ); } public void someMethod() { if( getAttribute().equals( "Some Value" ) ) { // do something... } } public void setAttribute( String s ) { this.someAttribute = s; } public String getAttribute() { String someAttribute = this.someAttribute; if( someAttribute == null ) { setAttribute( createDefaultValue() ); } return someAttribute; } protected String createDefaultValue() { return "Some Default Value"; } } All duplicate checks for null are superfluous: getAttribute() ensures the value is never null at a single location within the containing class. Efficiency arguments should be fairly moot -- modern compilers and virtual machines can inline the code when possible. As long as variables are never referenced directly, this also allows for proper application of the Open-Closed Principle. Question What are the disadvantages of self-encapsulation, if any? (Ideally, I would like to see references to studies that contrast the robustness of similarly complex systems that use and don't use self-encapsulation, as this strikes me as a fairly straightforward testable hypothesis.)

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• Why represent shopping carts and order invoices differently in a domain model?

  - by Todd

  I've built some shopping cart systems in the past, but I always designed them such that the final order invoice is just a shopping cart that has been marked as "purchased". All the logic for adding/removing/changing items in a cart is also the logic for the order. All data is stored in the same tables in the database. But it seems this is not the proper way to design an e-commerce site.. Can someone explain the benefit of separating the shopping cart from invoices in the domain model? It seems to me this would lead to a lot of duplicated code, an extra set of tables in the database, and make it harder to maintain in the event the system need to start accommodating more complicated orders (like specifying selected options for an item which may or may not change the price/availability/shipping time of the order). I'm assuming I just haven't seen the light, as every book and other example I see seems to separate these two seemingly similar concerns -- but I can't find any explanation as to the benefit of doing such! It's also the case in the systems that I design that changes are often made after the initial order is confirmed. It's not uncommon for items to be removed, replaced, or added afterwards (but prior to fulfillment).

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• What's the "correct way" to organize this project?

  - by user571747

  I'm working on a project that allows multiple users to submit large data files and perform operations on them. The "backend" which performs these operations is written in Perl while the "frontend" uses PHP to load HTML template files and determines which content to deliver. Data is stored in a database (MySQL, SQLite, Oracle) and while there is data which has not yet been acted upon, Perl adds it to a running queue which delivers data to other threads based on system load. In addition, there may be pre- and post-processing of the data before and after the main Perl script operates (the specifications are unclear) so I may want to allow these processors to be user-selectable plugins. I had been writing this project in a more procedural fashion but I am quickly realizing the benefit of separating concerns as to limit the scope one change has on the rest of the project. I'm quite unexperienced with design patterns and am curious what the best way to proceed is. I've heard MVC thrown around quite a bit but I am unsure of how to apply it. Specifically, what are some good options to structure this code (in terms of design patterns and folder hierarchy)? How can I achieve this with both PHP and Perl while minimizing duplicated code between languages? Should I keep my PHP files in the top level so I don't have ugly paths in the URL? Also, if I want to provide interchangeable databases, does each table need its own DAO implementation?

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• Google I/O 2010 - Google Wave API design principles

  Google I/O 2010 - Google Wave API design principles Google I/O 2010 - Google Wave API design principles + anatomy of a great extension Wave 201 Pamela Fox, Michael Goderbauer (Hasso Plattner Institute) Google Wave is all about collaboration. The most successful extensions are user-friendly and collaborative. Wave robots should be as intuitive to communicate with as a human, and play well with other robots; Wave gadgets should extend the metaphors of the textual collaboration into the visual. In this talk, we'll discuss the design and privacy principles you should consider while building extensions, and show examples of extensions that demonstrate these principles. For all I/O 2010 sessions, please go to code.google.com/events/io/2010/sessions.html From: GoogleDevelopers Views: 6 0 ratings Time: 01:01:54 More in Science & Technology

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• Fluid VS Responsive Website Development Questions

  - by Aditya P

  As I understand these form the basis for targeting a wide array of devices based on the browser size, given it would be a time consuming to generate different layouts targeting different/specific devices and their resolutions. Questions: Firstly right to the jargon, is there any actual difference between the two or do they mean the same? Is it safe to classify the current development mainly a html5/css3 based one? What popular frameworks are available to easily implement this? What testing methods used in this regard? What are the most common compatibility issues in terms of different browser types? I understand there are methods like this http://css-tricks.com/resolution-specific-stylesheets/ which does this come under?. Are there any external browser detection methods besides the API calls specific to the browser that are employed in this regard? Points of interest [Prior Research before asking these questions] Why shouldn't "responsive" web design be a consideration? Responsive Web Design Tips, Best Practices and Dynamic Image Scaling Techniques A recent list of tutorials 30 Responsive Web Design and Development Tutorials by Eric Shafer on May 14, 2012 Update Ive been reading that the basic point of designing content for different layouts to facilitate a responsive web design is to present the most relevant information. now obviously between the smallest screen width and the highest we are missing out on design elements. I gather from here http://flashsolver.com/2012/03/24/5-top-commercial-responsive-web-designs/ The top of the line design layouts (widths) are desktop layout (980px) tablet layout (768px) smartphone layout – landscape (480px) smartphone layout – portrait (320px) Also we have a popular responsive website testing site http://resizemybrowser.com/ which lists different screen resolutions. I've also come across this while trying to find out the optimal highest layout size to account for http://stackoverflow.com/questions/10538599/default-web-page-width-1024px-or-980px which brings to light seemingly that 1366x768 is a popular web resolution. Is it safe to assume that just accounting for proper scaling from width 980px onwards to the maximum size would be sufficient to accommodate this? given we aren't presenting any new information for the new size. Does it make sense to have additional information ( which conflicts with purpose of responsive web design) to utilize the top size and beyond?

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• The Foundation of an OSGi-Based Application: Design and Bundles

  Learn how to lay the necessary groundwork for service-oriented, modular OSGi components in the Eclipse Equinox container.

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• cross resolution level design advice [on hold]

  - by Mike

  I was looking for some beginner advice regarding level design across multiple resolutions. I believe the answer is likely "it depends", but any input from anyone with real experience is very appreciated. Basically, I am building a 2D Super Metroid type game. If rooms/levels are to be a tiled grid, what are some general best practices for designing rooms when taking into account different resolutions? Since more or less tiles could fit vertically on a single screen depending on the resolution, is it better to design towards possibly having more of the room visible depending on the screen (with a bare minimum needed for gameplay), or should I fix the design at a certain tile height and scale the graphics?

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• Component-based design: handling objects interaction

  - by Milo

  I'm not sure how exactly objects do things to other objects in a component based design. Say I have an Obj class. I do: Obj obj; obj.add(new Position()); obj.add(new Physics()); How could I then have another object not only move the ball but have those physics applied. I'm not looking for implementation details but rather abstractly how objects communicate. In an entity based design, you might just have: obj1.emitForceOn(obj2,5.0,0.0,0.0); Any article or explanation to get a better grasp on a component driven design and how to do basic things would be really helpful.

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• Question about component based design: handling objects interaction

  - by Milo

  I'm not sure how exactly objects do things to other objects in a component based design. Say I have an Obj class. I do: Obj obj; obj.add(new Position()); obj.add(new Physics()); How could I then have another object not only move the ball but have those physics applied. I'm not looking for implementation details but rather abstractly how objects communicate. In an entity based design, you might just have: obj1.emitForceOn(obj2,5.0,0.0,0.0); Any article or explanation to get a better grasp on a component driven design and how to do basic things would be really helpful.

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• Google I/O 2012 - Advanced Design for Engineers

  Google I/O 2012 - Advanced Design for Engineers Alex Faaborg, Christian Robertson Design isn't black magic, it's a field that people can learn. In this talk two elite designers from Google will give you an advanced crash course in interactive and visual design. Topics will include mental models, natural mappings, metaphors, mode errors, visual hierarchies, typography and gestalt principles. Correctly applied this knowledge can drastically improve the quality of your work. For all I/O 2012 sessions, go to developers.google.com From: GoogleDevelopers Views: 158 9 ratings Time: 55:50 More in Science & Technology

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• Google I/O 2012 - Android Design for Success

  Google I/O 2012 - Android Design for Success Rachel Garb, Jens Nagel, Nate Streu, Matias Duarte You have a great idea for an Android app. You want it to stand out among hundreds of thousands. You want your users to love it and tell everyone they know. The Android User Experience team is here to help. We'll talk about the Android Design guide and other tricks of the trade for creating apps that delight users and help them accomplish their goals. No design background is required. For all I/O 2012 sessions, go to developers.google.com From: GoogleDevelopers Views: 46 5 ratings Time: 01:03:04 More in Science & Technology

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• Windows Phone 7 Design Template

  Windows Phone 7 Design Template Expression Blend is a wonderful design environment for WP7 (Windows Phone 7) but for quickly visualizing a concept nothing beats Illustrator! I am excited about WP7 and decided that having a solid .ai template would prove invaluable. Some of the details of the WP7 UI Design and Interaction Guide are a bit fuzzy (literally) but I was able to generate some useful layout guides, character styles, and symbols. While the template does not cover every aspect of the guide I think it is a good launching point; if you find it useful and extend it please share your updates (I created the template in CS4, if you have problems in earlier versions let me know).Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Is PPC effective marketing Web Design & Development Services

  - by Pennf0lio

  Have anyone tried to do a PPC campaign on services like, Web Design Web Development Graphic Design Logo Design Programming as an individual and not a company? I've seen companies advertise web services, one popular i've seen is PSD2HTML. But I was if it is also applicable to individuals trying to market it self. If its applicable to, can you give some example how it is being maximize. Thank You! edit: I'd like to know if PPC campaign is effective on services mentioned above as an individual and not a company.

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• AdventueWorks Design Patterns Project - Part 1

  - by RonGarlit

  This is the presentation I did tonight at PHILLYNJ.NET.  It is the first in a multi-part of a series on the Applied Design Patterns.   The solution files are working code with design pattern notes in the comment blocks. After the overview and higher level discussions on Enterprise Design Patterns I reviewed the low level Database Access Library of code.  With walk-throughs of the the code and unint test. After that we went through the ProductPhotoConsoleTest Application that performed intergration testing of the DBAccess Class with the AdventureWorks ProductPhoto table extracting the photos and writing them to a file folder. The Demo code and PowerPoint can be obained from this link.  https://skydrive.live.com/?wa=wsignin1.0&cid=29e34e9a8650bb9e#!/?cid=29e34e9a8650bb9e&sc=documents&id=29E34E9A8650BB9E%21151 Please note that I use Visual Studio 2010 Ultimate.  If you have a lesser version the Modeling projects likely will not work or have limited functionality and you should unload that project to prevent warning. Enjoy! --Ron

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