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  • Comparing Design Patterns

    - by Lijo
    Hi, I am learning design patterns using C#. One of the challenges that I am facing is that they look similar. Could you please help me to distinguish them – basically when to use them? - Why not the other? Bridge and Strategy State and Strategy Façade and Strategy Composite and Strategy I understand that there are lots of resources available in the web. However they does not treat this special question. [Note: I am looking for implementation examples and rationale behind the selection; not mere explanations] It would be great if you are taking examples from any of the following 1) E-Commerce 2) Payroll system 3) Banking 4) Retailing Thanks for your understanding.. Thanks Lijo

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  • How to design model for multi-tiered data?

    - by Chris
    Say I have three types of object: Area, Subarea and Topic. I want to be able to display an Area, which is just a list of Subareas and the Topics contained in those Subareas. I never want to be able to display Subareas separately - they're just for breaking up the Topics. Topics can, however, appear in multiple Areas (but probably under the same Subarea). How would I design a model for this? I could use ForeignKey from Topic to Subarea and from Subarea to Area, but it seems unnecessarily complex given that I never want to interact with subareas themselves. Also, none of these objects are ever altered or added to by the user. They're just for me to represent information. Maybe there is a better way to represent it all?

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  • which design choose? - pros and cons

    - by Guarava Makanili
    Which of these 3 approches would choose and why? // This is the one I would choose class Car { } class FeeCalculator { public double calculateFee(Car car) { return 0; } } // in that case the problem might be when we use ORM framework and we try to invoke save with parameter Car class Car { private FeeCalculator calculator; public double calculateFee() { return calculator.calculateFee(this); } } class FeeCalculator { public double calculateFee(Car car) { return 0; } } // in that case the problem mentioned above is solved, but I don't like this design class Car { public double calculateFee(FeeCalculator calculator) { return calculator.calculateFee(this); } } class FeeCalculator { public double calculateFee(Car car) { return 0; } }

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  • Class design question (Disposable and singleton behavior)

    - by user137348
    The Repository class has singleton behavior and the _db implements the disposable pattern. As excepted the _db object gets disposed after the first call and because of the singleton behavior any other call of _db will crash. [ServiceBehavior(InstanceContextMode=InstanceContextMode.Single)] public class Repository : IRepository { private readonly DataBase _db; public Repository(DataBase db) { _db = db; } public int GetCount() { using(_db) { return _db.Menus.Count(); } } public Item GetItem(int id) { using(_db) { return _db.Menus.FirstOrDefault(x=>x.Id == id); } } } My question is, is there any way to design this class to work properly without removing the singleton behavior? The Repositoryclass will be serving big amount of requests.

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  • related categories - database design

    - by mike
    Hello! I'm looking for a little database design advice... I have a spreadsheet with a few columns in it. Column 1 being a list of categories and the rest being related categories(to the category in column 1). I'm trying to figure out what the best way to setup the tables would be... My thought so far is to have a table that just lists the categories then have a table with 2 columns that holds the id of the category and the id of a related category.... Would this be the best way to do this? Any better ideas?

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  • Generic Database table design

    - by Gazeth
    Just trying to figure out the best way to design my table for the following scenario: I have several areas in my system (documents, projects, groups and clients) and each of these can have comments logged against them. My question is should I have one table like this: CommentID DocumentID ProjectID GroupID ClientID etc Where only one of the ids will have data and the rest will be NULL or should I have a seperate CommentType table and have my comments table like this: CommentID CommentTypeID ResourceID (this being the id of the project/doc/client) etc My thoughts are that option 2 would be more efficient from an indexing point of view?

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  • Customers and suppliers database design issue

    - by hectorsq
    I am developing a web application in which I will have customers and suppliers. Initially I thought on using a Customers table and a Suppliers table. Then when I was thinking on bank transactions, I noticed that each transaction needs to refer to a customer or a supplier, so I thought on using a single table named Business in which I will save both customers and suppliers. If I use Customers and Suppliers tables when I want to list the bank transactions I will have to search in both tables to get the company name. If I use a Businesses table I will have to use a business type column, and have the union of possible fields for all businesses types. Any suggestions on the design?

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  • C++ Singleton design pattern

    - by Artem Barger
    Recently I've bumped into a realization/implementation of the Singleton design pattern for C++. It has looked like this (I have adopted it from the real life example): // a lot of methods are omitted here class Singleton { public: static Singleton* getInstance( ); ~Singleton( ); private: Singleton( ); static Singleton* instance; }; From this declaration I can deduce that the instance field is initiated on the heap. That means there is a memory allocation. What is completely unclear for me is when exactly the memory is going to be deallocated? Or is there a bug and memory leak? It seems like there is a problem in the implementation. My main question is, how do I implement it in the right way?

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  • Does the following indicate a bad design?

    - by Mewzer
    Hello, I was wondering whether you think the following code usually indicates a bad design ... class X { public: ... private: Y y; }; Class Y { public: Y( X& value ){ x = value; }; private: X& x; } (i.e. there is some sort of cyclic dependency between the classes X and Y).

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  • Which are the best tools for Graphic Designing?

    - by Jen
    Hello, I want to take up Graphic Designing as my profession. I would be designing Logos, Icons, Stationery, Brochures, Handouts, Book Covers, etc. But I am thoroughly confused as to which tools are the best and which books/resources will help me learn these tools and graphic designing like a professional. I am ready to shell out money to purchase the resources. Please help me out! Thanks, Jen

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  • Oracle Database Security Protecting the Oracle IRM Schema

    - by Simon Thorpe
    Acquiring the Information Rights Management technology in 2006 was part of Oracle's strategic security vision and IRM compliments nicely the overall Oracle security set of solutions. A year ago I spoke about how Oracle has solutions that can help companies protect information throughout its entire life cycle. With our acquisition of Sun this set of solutions has solidified and has even extended down to the operating system and hardware level. Oracle can now offer customers technology that protects their data from the disk, through the database to documents on the desktop! With the recent release of Oracle IRM 11g I was tasked to configure demonstration and evaluation environments and I thought it would make a nice story to leverage some of the security features in the latest release of the Oracle Database. After building these environments I thought I would put together a simple video demonstrating how both Database Advanced Security and Information Rights Management combined can provide a very secure platform for protecting your information. Have a look at the following which highlights these database security options.Transparent Data Encryption protecting the communication from the Oracle IRM server to the Database server. Encryption techniques provide confidentiality and integrity of the data passing to and from the IRM service on the back end. Transparent Data Encryption protecting the Oracle IRM database schema. Encryption is used to provide confidentiality of the IRM data whilst it resides at rest in the database table space. Database Vault is used to ensure only the Oracle IRM service has access to query and update the information that resides in the database. This is an excellent method of ensuring that database administrators cannot look at or make changes to the Oracle IRM database whilst retaining their ability to administrate the database. The last thing you want after deploying an IRM solution is for a curious or unhappy DBA to run a query that grants them rights to your company financial data or documents pertaining to a merger or acquisition.

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  • Handling element collisions on importing/including XML schemas

    - by eggyal
    Given schema definitions that define the same element differently, can one import/include both definitions and reference them independently from within a third schema definition? For example, given: <schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="urn:example:namespace"> <element name="message" type="boolean"/> </schema> and: <schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="urn:example:namespace"> <element name="message" type="date"/> </schema> Can one construct the following: <schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="urn:example:namespace"> <complexType name="booleanMessageType"> <xs:sequence> <!-- reference to first definition here --> </xs:sequence> </complexType> <complexType name="dateMessageType"> <xs:sequence> <!-- reference to second definition here --> </xs:sequence> </complexType> </schema>

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  • Database model for keeping track of likes/shares/comments on blog posts over time

    - by gage
    My goal is to keep track of the popular posts on different blog sites based on social network activity at any given time. The goal is not to simply get the most popular now, but instead find posts that are popular compared to other posts on the same blog. For example, I follow a tech blog, a sports blog, and a gossip blog. The tech blog gets waaay more readership than the other two blogs, so in raw numbers every post on the tech blog will always out number views on the other two. So lets say the average tech blog post gets 500 facebook likes and the other two get an average of 50 likes per post. Then when there is a sports blog post that has 200 fb likes and a gossip blog post with 300 while the tech blog posts today have 500 likes I want to highlight the sports and gossip blog posts (more likes than average vs tech blog with more # of likes but just average for the blog) The approach I am thinking of taking is to make an entry in a database for each blog post. Every x minutes (say every 15 minutes) I will check how many likes/shares/comments an entry has received on all the social networks (facebook, twitter, google+, linkeIn). So over time there will be a history of likes for each blog post, i.e post 1234 after 15 min: 10 fb likes, 4 tweets, 6 g+ after 30 min: 15 fb likes, 15 tweets, 10 g+ ... ... after 48 hours: 200 fb likes, 25 tweets, 15 g+ By keeping a history like this for each blog post I can know the average number of likes/shares/tweets at any give time interval. So for example the average number of fb likes for all blog posts 48hrs after posting is 50, and a particular post has 200 I can mark that as a popular post and feature/highlight it. A consideration in the design is to be able to easily query the values (likes/shares) for a specific time-frame, i.e. fb likes after 30min or tweets after 24 hrs in-order to compute averages with which to compare against (or should averages be stored in it's own table?) If this approach is flawed or could use improvement please let me know, but it is not my main question. My main question is what should a database scheme for storing this info look like? Assuming that the above approach is taken I am trying to figure out what a database schema for storing the likes over time would look like. I am brand new to databases, in doing some basic reading I see that it is advisable to make a 3NF database. I have come up with the following possible schema. Schema 1 DB Popular Posts Table: Post post_id ( primary key(pk) ) url title Table: Social Activity activity_id (pk) url (fk) type (i.e. facebook,twitter,g+) value timestamp This was my initial instinct (base on my very limited db knowledge). As far as I under stand this schema would be 3NF? I searched for designs of similar database model, and found this question on stackoverflow, http://stackoverflow.com/questions/11216080/data-structure-for-storing-height-and-weight-etc-over-time-for-multiple-users . The scenario in that question is similar (recording weight/height of users overtime). Taking the accepted answer for that question and applying it to my model results in something like: Schema 2 (same as above, but break down the social activity into 2 tables) DB Popular Posts Table: Post post_id (pk) url title Table: Social Measurement measurement_id (pk) post_id (fk) timestamp Table: Social stat stat_id (pk) measurement_id (fk) type (i.e. facebook,twitter,g+) value The advantage I see in schema 2 is that I will likely want to access all the values for a given time, i.e. when making a measurement at 30min after a post is published I will simultaneous check number of fb likes, fb shares, fb comments, tweets, g+, linkedIn. So with this schema it may be easier get get all stats for a measurement_id corresponding to a certain time, i.e. all social stats for post 1234 at time x. Another thought I had is since it doesn't make sense to compare number of fb likes with number of tweets or g+ shares, maybe it makes sense to separate each social measurement into it's own table? Schema 3 DB Popular Posts Table: Post post_id (pk) url title Table: fb_likes fb_like_id (pk) post_id (fk) timestamp value Table: fb_shares fb_shares_id (pk) post_id (fk) timestamp value Table: tweets tweets__id (pk) post_id (fk) timestamp value Table: google_plus google_plus_id (pk) post_id (fk) timestamp value As you can see I am generally lost/unsure of what approach to take. I'm sure this typical type of database problem (storing measurements overtime, i.e temperature statistic) that must have a common solution. Is there a design pattern/model for this, does it have a name? I tried searching for "database periodic data collection" or "database measurements over time" but didn't find anything specific. What would be an appropriate model to solve the needs of this problem?

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  • How should I prepare the design of a web page for a web developer?

    - by jackal
    What techniques, software or practices do you use to prepare a description of a web page for further development? I am doing some research (with little luck) in how to create description for web developers - what should be included on the web page (inputs widths, font sizes, images placement, etc). Right now I use a combination of Excel and Word documents. In complex cases this is inefficient. Any other suggestions?

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  • Where can I ask web design questions of a more amateur nature?

    - by Warren van Rooyen
    I don't want to bother pro web designers with simple questions as I see most of the questions here are quite technical. An example would be, 'I have a template I've downloaded. The folder contains a css folder and PHP files. How would I bring this into Dreamweaver?' It's unfortunately in a space between what I'd be able to find on Google and asking here without feeling like a hinderance for those who don't want to answer such simple questions. Thanks, Warren.

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  • Design Anti-Patterns - C# - Do you call this a God object?

    - by Reddy S R
    I am writing Portfolio module for my web site and it has 3 components. Gallery Category, Gallery, & Gallery Images. I am doing all the request handling, (creating, reading, updating, other), for the above 3 components in 1 class, Portfolio. DB handling jobs for Portfolio module is done in another file. My question is, even just for request handling purpose, can you do all the operations in 1 class? -Reddy

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  • What are the design decisions involved in choosing how to expose a Java web application?

    - by Gary Rowe
    There are many ways to expose a Java web application to the consumer: application container (JBoss etc), servlet container (Tomcat etc), OSGi (Knopflerfish etc), self-executable WAR (Winstone etc) and so on. Are there any clear considerations where one approach should be favoured over another? As an example, could a collection of self-executable WARs running as raw Unix processes outperform the same applications deployed within Tomcat taking into account administration and scalability concerns?

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  • Is there a clean separation of my layers with this attempt at Domain Driven Design in XAML and C#

    - by Buddy James
    I'm working on an application. I'm using a mixture of TDD and DDD. I'm working hard to separate the layers of my application and that is where my question comes in. My solution is laid out as follows Solution MyApp.Domain (WinRT class library) Entity (Folder) Interfaces(Folder) IPost.cs (Interface) BlogPosts.cs(Implementation of IPost) Service (Folder) Interfaces(Folder) IDataService.cs (Interface) BlogDataService.cs (Implementation of IDataService) MyApp.Presentation(Windows 8 XAML + C# application) ViewModels(Folder) BlogViewModel.cs App.xaml MainPage.xaml (Contains a property of BlogViewModel MyApp.Tests (WinRT Unit testing project used for my TDD) So I'm planning to use my ViewModel with the XAML UI I'm writing a test and define my interfaces in my system and I have the following code thus far. [TestMethod] public void Get_Zero_Blog_Posts_From_Presentation_Layer_Returns_Empty_Collection() { IBlogViewModel viewModel = _container.Resolve<IBlogViewModel>(); viewModel.LoadBlogPosts(0); Assert.AreEqual(0, viewModel.BlogPosts.Count, "There should be 0 blog posts."); } viewModel.BlogPosts is an ObservableCollection<IPost> Now.. my first thought is that I'd like the LoadBlogPosts method on the ViewModel to call a static method on the BlogPost entity. My problem is I feel like I need to inject the IDataService into the Entity object so that it promotes loose coupling. Here are the two options that I'm struggling with: Not use a static method and use a member method on the BlogPost entity. Have the BlogPost take an IDataService in the constructor and use dependency injection to resolve the BlogPost instance and the IDataService implementation. Don't use the entity to call the IDataService. Put the IDataService in the constructor of the ViewModel and use my container to resolve the IDataService when the viewmodel is instantiated. So with option one the layers will look like this ViewModel(Presentation layer) - Entity (Domain layer) - IDataService (Service Layer) or ViewModel(Presentation layer) - IDataService (Service Layer)

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  • What is the best way to design a table with an arbitrary id?

    - by P.Brian.Mackey
    I have the need to create a table with a unique id as the PK. The ID is a surrogate key. Originally, I had a natural key, but requirement changes have undermined this idea. Then, I considered adding an auto incrementing identity. But, this presents problems. A. I can't specify my own ID. B. The ID's are difficult to reset. Both of these together make it difficult to copy over this table with new data or move the table across domains, e.g. Dev to QA. I need to refer to these ID's from the front end, JavaScript...so they must not change. So, the only way I am aware of to meet all these challenges is to make a GUID ID. This way, I can overwrite the ID's when I need to or I can generate a new one without concern for order (E.G. an int based id would require I know the last inserted ID). Is a GUID the best way to accomplish my goals? Considering that a GUID is a string and joining on a string is an expensive task, is there a better way?

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  • How can I refactor client side functionality to create a product line-like generic design?

    - by Nupul
    Assume the following situation similar to that of Stack Overflow: I have a system with a front-end that can perform various manipulations on the data (by sending messages to REST back-end): Posting Editing and deleting Adding labels and tags Now in the first version we created it well modularized but the need as of now for 'evolving' the system similar to Stack Overflow. My question is how best to separate the commonality and how to incorporate the variability with respect to the following: Commonality: The above 'functionalities' and sending/receiving the data from the server Look and feel (also a variability as explained below) HTTP verbs associated with the above actions Variability: The RESTful URLs where the requests are sent The text/style of the UI (the commonality is analogous to Stack Overflow - the functionality of upvotes, posting a question remains the same, but the words, the icons, the look and feel is still different across sites) I think this is entirely a client-side code organization/refactoring issue. I'm heavily using jQuery, javascript and backbone for front-end development. My question is how best should I isolate the same to be able to create multiple such aspects to the tool we are currently working on?

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  • What is the proper name for this design pattern in Python?

    - by James
    In Python, is the proper name for the PersonXXX class below PersonProxy, PersonInterface, etc? import rest class PersonXXX(object): def __init__(self,db_url): self.resource = rest.Resource(db_url) def create(self,person): self.resource.post(person.data()) def get(self): pass def update(self): pass def delete(self): pass class Person(object): def __init__(self,name, age): self.name = name self.age = age def data(self): return dict(name=self.name,age=self.age)

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  • What is the typical example of old school website design ?

    - by Pierre 303
    I want to build a website for a retro thing that was popular in the mid 90s (beginning of the commercial internet). So I want use old designs that was very popular at that time. The first thing that comes to my mind was those "under construction" animated gifs. People often put animated gifs everywhere. But also those awful repeating backgrounds. So yes, I want my website to look exactly like in the mid nineties ;) (please suggest practical and usable features, I guess an Java Applet menu would not work today, or saying on the bottom that this website is optimized for Netscape 3) EDIT: for those that wants to see the result: Retrology

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  • Is it normal to think about a design problem for days with no code written? [closed]

    - by Kim Jong Woo
    Sometimes I stare blankly into space or sketch ideas and write some pseudo codes on paper. Then I scratch it out and start again, then when I think I have the correct solution for the problem I begin writing the code. Is it normal to think for days without writing any code? Is this a sign that I am approaching the problem entirely wrong? It makes me nervous to not getting any tangible code written in my IDE.

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  • How to make this CSS design of words in headings look clean and well desinged? [closed]

    - by kacalapy
    I am trying to get the lipstick on the pig and not wearing my UI developer hat often is making this impossible. Can someone give me nice alternatives to the code below. this is what i have now. <style> .FirstLetter:first-letter{font-family: arial; font-size: 14pt; font-weight: bold;color:White; background:Blue; border:1px black solid; padding-top:8px; padding-left:8px; padding-bottom:3px;} .Spaced{letter-spacing: 5px;font-family: arial; font-size: 14pt; font-weight: bold;} </style> <div class="FirstLetter Spaced headerFont"> Executive Summary </div> Here is the ugly result of the above code- i am lookign to make the header section look better ONLY that's where the first letter is blue:

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  • What is the typical example of old school website design?

    - by Pierre 303
    I want to build a website for a retro thing that was popular in the mid 90s (beginning of the commercial internet). So I want use old designs that was very popular at that time. The first thing that comes to my mind was those "under construction" animated gifs. People often put animated gifs everywhere. But also those awful repeating backgrounds. So yes, I want my website to look exactly like in the mid nineties ;) (please suggest practical and usable features, I guess an Java Applet menu would not work today, or saying on the bottom that this website is optimized for Netscape 3) EDIT: for those that wants to see the result: Retrology

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