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  • Entity Attribute Value Database vs. strict Relational Model Ecommerce question

    - by Dr. Zim
    It is safe to say that the EAV/CR database model is bad. That said, Question: What database model, technique, or pattern should be used to deal with "classes" of attributes describing e-commerce products which can be changed at run time? In a good E-commerce database, you will store classes of options (like TV resolution then have a resolution for each TV, but the next product may not be a TV and not have "TV resolution"). How do you store them, search efficiently, and allow your users to setup product types with variable fields describing their products? If the search engine finds that customers typically search for TVs based on console depth, you could add console depth to your fields, then add a single depth for each tv product type at run time. There is a nice common feature among good e-commerce apps where they show a set of products, then have "drill down" side menus where you can see "TV Resolution" as a header, and the top five most common TV Resolutions for the found set. You click one and it only shows TVs of that resolution, allowing you to further drill down by selecting other categories on the side menu. These options would be the dynamic product attributes added at run time. Further discussion: So long story short, are there any links out on the Internet or model descriptions that could "academically" fix the following setup? I thank Noel Kennedy for suggesting a category table, but the need may be greater than that. I describe it a different way below, trying to highlight the significance. I may need a viewpoint correction to solve the problem, or I may need to go deeper in to the EAV/CR. Love the positive response to the EAV/CR model. My fellow developers all say what Jeffrey Kemp touched on below: "new entities must be modeled and designed by a professional" (taken out of context, read his response below). The problem is: entities add and remove attributes weekly (search keywords dictate future attributes) new entities arrive weekly (products are assembled from parts) old entities go away weekly (archived, less popular, seasonal) The customer wants to add attributes to the products for two reasons: department / keyword search / comparison chart between like products consumer product configuration before checkout The attributes must have significance, not just a keyword search. If they want to compare all cakes that have a "whipped cream frosting", they can click cakes, click birthday theme, click whipped cream frosting, then check all cakes that are interesting knowing they all have whipped cream frosting. This is not specific to cakes, just an example.

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  • Help me with a solution for what could be solutioned by virtual static fields... in FPC

    - by Gregory Smith
    Hi I'm doing an event manager in Freepascal Each event is an object type TEvent (=object), each kind of event must derive from this class. Events are differentiated by an integer identificator, assigned dynamically. The problem is that i want to retrieve the event id of an instance, and i can't do it well. All instances of a class(object) have a unique id = so it should be static field. All classes have a diferent id = so it should be virtual. Event ids are assignated in run time, and can change = so it can't be a simple method In sum, I can't put all this together. I'm looking for an elegant solution, i don't want to write a hardcoded table, actualizing it in every constructor... etc, i'd prefer something taking advantage of the polymorphism Can anyone help me with another technical or design solution? I remark I don't want to use class instead of object construct.(property doesn't work on objects? :(

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  • Designing a state machine in C++

    - by skyeagle
    I have a little problem that involves modelling a state machine. I have managed to do a little bit of knowledge engineering and 'reverse engineer' a set of primitive deterministic rules that determine state as well as state transitions. I would like to know what the best practises are regarding: How to rigorously test my states and state transitions to make sure that the system cannot end up in an undeetermined state. How to enforce state transition requirements (for example, it should be impossible to go directly from stateFoo to StateFooBar, i.e. to embue each state with 'knowlege' about the states it can transition to. Ideally, I would like to use clean, pattern based design, with templates wherever possible. I do need somewhere to start though and I would be grateful for any pointers (no pun intended), that are sent my way.

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  • abstract method signature, inheritance, and "Do" naming convention

    - by T. Webster
    I'm learning about design patterns and in examples of code I've seen a convention where the abstract class declares a method, for example: public abstract class ServiceBase { ... public virtual object GetSomething(); and then protected abstract object DoGetSomething(); My question is on why these two methods exist, since they appear to serve the same purpose. Is this so that the base class GetSomething() method logic cannot be overridden by inherited classes? But then again, the method is marked virtual, so it can be overridden anyway. What is the usefulness here in requiring derived class implementers to implement the abstract method when the virtual method can be called anyway?

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  • overflow-x AND Middle Mouse Button Moving

    - by Rad The Mad
    My Page is 980px in Width, but I have a few design elements (which belong with the background). I positioned them with position: absolute;. This creates a horizontal scrollbar for those who have a =< 1024 resolution. I disabled that scrollbar with overflow-x:hidden on (and for IE7 and etc). However, when I hold my middle mouse button,(i think this applies to laptop touchpads as well) it let's me move around to the right, is it possible to fix this with anything? (javascript, css)? Tested this issues in Chrome, IE, Firefox.

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  • How to apply Abstract Factory Pattern ???

    - by Amit
    I am new to Design Pattern and I have a scenario here... and not sure as how to implement the pattern ... We have multiple vendors Philips, Onida... Each vendor (philips, onida...) may have different type of product i.e. Plasma or Normal TV I want specific product of each vendor using Abstract Factory Pattern... Thanks in advance for any help... My implementation so far... public enum TvType { Samsung = 0,LG = 1,Philips = 2, Sony = 3 } public enum Product { Plasma = 0,NormalTV = 1 } concrete class of each vendor.... that returns each product and also the interface that contains ProductInfo i.e. if Vendor is ... then it must have this product....

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  • What patterns exist for web application development?

    - by DaveDev
    I understand that MVC & MVP are design patterns that are commonly used for web development, as well as ASP.NET WebForms (more of an anti-pattern, really!). What other patterns are used in web application development? I'm not necessarily saying I want to learn/use new patterns just to be different - I do believe there's a lot of value in taking the conventional route - but I think it's good to know what else is out there to be able to properly understand what I'm currently working with. Thanks.

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  • How to implement "drag n drop" user interface on website?

    - by Nikkeloodeni
    Hello, I was wondering what would be the best way to implement some kind of "drag n drop" user interface? What i mean is that there would be one main page and every link click (eg. other sections like about, gallery, contact form) would open a new drag n drop element on top of that main page. Something like windows desktop where you can move your application windows around the screen. Would it be best to call different functions with AJAX when a link is clicked? Like "gallery" link would call gallery-function and retrieve dynamically generated contents of that "window" with AJAX call and then just load that stuff on some div? Or would some other type of approach suit better for this? I hope I was able to explain this clearly enough. I'm looking for a proper "design pattern" to implement this. All suggestions are wellcome! :)

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  • How to program a connection pool?

    - by the_drow
    Is there a known algorithm for implementing a connection pool? If not what are the known algorithms and what are their trade-offs? What design patterns are common when designing and programming a connection pool? Are there any code examples implement a connection pool using boost.asio? Is it a good idea to use a connection pool for presisting connections (not http)? How is threading related to connection pooling? When do you need a new thread?

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  • how to store data with many categories and many properties efficiently?

    - by Mickey Shine
    We have a large number of data in many categories with many properties, e.g. category 1: Book properties: BookID, BookName, BookType, BookAuthor, BookPrice category 2: Fruit properties: FruitID, FruitName, FruitShape, FruitColor, FruitPrice We have many categories like book and fruit. Obviously we can create many tables for them (MySQL e.g.), and each category a table. But this will have to create too many tables and we have to write many "adapters" to unify manipulating data. The difficulties are: 1) Every category has different properties and this results in a different data structure. 2) The properties of every categoriy may have to be changed at anytime. 3) Hard to manipulate data if each category a table (too many tables) How do you store such kind of data?

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  • Many-to-many relationship in oop

    - by Manu
    what is best way to model many-to-many relationship? lets say we have a two classes , Team and Player any given Player can be in multiple Team s any Team can have as many Player s as they like I like to call methods like playerX.getTeamList() to get the list of all the Team s he/she is in teamY.getPlayerList() to get the list of all the Player s in the team (or have some other way to do this effectively) I can think of two ways of doing this , but they just don't feels like good oop pattens. can you think of any good ways , perhaps a design patten ?

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  • Should I share UI for objects that use common fields?

    - by wb
    I have a parent class that holds all of the fields that are common between all device types. From that, I have a few derived classes that each hold their unique fields. Say I have device type "Switch" and "Transformer". Both derived classes only have 2-3 of their own unique fields. When doing the UI design (windows forms) in this case. Should I create two separate forms for each device type or create a user control with all fields that are shared among all devices? Thank you.

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  • Five Key Strategies in Master Data Management

    - by david.butler(at)oracle.com
    Here is a very interesting Profit Magazine article on MDM: A recent customer survey reveals the deleterious effects of data fragmentation. by Trevor Naidoo, December 2010   Across industries and geographies, IT organizations have grown in complexity, whether due to mergers and acquisitions, or decentralized systems supporting functional or departmental requirements. With systems architected over time to support unique, one-off process needs, they are becoming costly to maintain, and the Internet has only further added to the complexity. Data fragmentation has become a key inhibitor in delivering flexible, user-friendly systems. The Oracle Insight team conducted a survey assessing customers' master data management (MDM) capabilities over the past two years to get a sense of where they are in terms of their capabilities. The responses, by 27 respondents from six different industries, reveal five key areas in which customers need to improve their data management in order to get better financial results. 1. Less than 15 percent of organizations surveyed understand the sources and quality of their master data, and have a roadmap to address missing data domains. Examples of the types of master data domains referred to are customer, supplier, product, financial and site. Many organizations have multiple sources of master data with varying degrees of data quality in each source -- customer data stored in the customer relationship management system is inconsistent with customer data stored in the order management system. Imagine not knowing how many places you stored your customer information, and whether a customer's address was the most up to date in each source. In fact, more than 55 percent of the respondents in the survey manage their data quality on an ad-hoc basis. It is important for organizations to document their inventory of data sources and then profile these data sources to ensure that there is a consistent definition of key data entities throughout the organization. Some questions to ask are: How do we define a customer? What is a product? How do we define a site? The goal is to strive for one common repository for master data that acts as a cross reference for all other sources and ensures consistent, high-quality master data throughout the organization. 2. Only 18 percent of respondents have an enterprise data management strategy to ensure that data is treated as an asset to the organization. Most respondents handle data at the department or functional level and do not have an enterprise view of their master data. The sales department may track all their interactions with customers as they move through the sales cycle, the service department is tracking their interactions with the same customers independently, and the finance department also has a different perspective on the same customer. The salesperson may not be aware that the customer she is trying to sell to is experiencing issues with existing products purchased, or that the customer is behind on previous invoices. The lack of a data strategy makes it difficult for business users to turn data into information via reports. Without the key building blocks in place, it is difficult to create key linkages between customer, product, site, supplier and financial data. These linkages make it possible to understand patterns. A well-defined data management strategy is aligned to the business strategy and helps create the governance needed to ensure that data stewardship is in place and data integrity is intact. 3. Almost 60 percent of respondents have no strategy to integrate data across operational applications. Many respondents have several disparate sources of data with no strategy to keep them in sync with each other. Even though there is no clear strategy to integrate the data (see #2 above), the data needs to be synced and cross-referenced to keep the business processes running. About 55 percent of respondents said they perform this integration on an ad hoc basis, and in many cases, it is done manually with the help of Microsoft Excel spreadsheets. For example, a salesperson needs a report on global sales for a specific product, but the product has different product numbers in different countries. Typically, an analyst will pull all the data into Excel, manually create a cross reference for that product, and then aggregate the sales. The exact same procedure has to be followed if the same report is needed the following month. A well-defined consolidation strategy will ensure that a central cross-reference is maintained with updates in any one application being propagated to all the other systems, so that data is synchronized and up to date. This can be done in real time or in batch mode using integration technology. 4. Approximately 50 percent of respondents spend manual efforts cleansing and normalizing data. Information stored in various systems usually follows different standards and formats, making it difficult to match the data. A customer's address can be stored in different ways using a variety of abbreviations -- for example, "av" or "ave" for avenue. Similarly, a product's attributes can be stored in a number of different ways; for example, a size attribute can be stored in inches and can also be entered as "'' ". These types of variations make it difficult to match up data from different sources. Today, most customers rely on manual, heroic efforts to match, cleanse, and de-duplicate data -- clearly not a scalable, sustainable model. To solve this challenge, organizations need the ability to standardize data for customers, products, sites, suppliers and financial accounts; however, less than 10 percent of respondents have technology in place to automatically resolve duplicates. It is no wonder, therefore, that we get communications about products we don't own, at addresses we don't reside, and using channels (like direct mail) we don't like. An all-too-common example of a potential challenge follows: Customers end up receiving duplicate communications, which not only impacts customer satisfaction, but also incurs additional mailing costs. Cleansing, normalizing, and standardizing data will help address most of these issues. 5. Only 10 percent of respondents have the ability to share data that was mastered in a master data hub. Close to 60 percent of respondents have efforts in place that profile, standardize and cleanse data manually, and the output of these efforts are stored in spreadsheets in various parts of the organization. This valuable information is not easily shared with the rest of the organization and, more importantly, this enriched information cannot be sent back to the source systems so that the data is fixed at the source. A key benefit of a master data management strategy is not only to clean the data, but to also share the data back to the source systems as well as other systems that need the information. Aside from the source systems, another key beneficiary of this data is the business intelligence system. Having clean master data as input to business intelligence systems provides more accurate and enhanced reporting.  Characteristics of Stellar MDM When deciding on the right master data management technology, organizations should look for solutions that have four main characteristics: enterprise-grade MDM performance complete technology that can be rapidly deployed and addresses multiple business issues end-to-end MDM process management with data quality monitoring and assurance pre-built MDM business relevant applications with data stores and workflows These master data management capabilities will aid in moving closer to a best-practice maturity level, delivering tremendous efficiencies and savings as well as revenue growth opportunities as a result of better understanding your customers.  Trevor Naidoo is a senior director in Industry Strategy and Insight at Oracle. 

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  • Doctrine Default Primary Key Problem (Again)

    - by 01010011
    Hi, Should I change all of my uniquely-named MySQL database primary keys to 'id' to avoid getting errors related to Doctrine's default primary key set in the plugin 'doctrine_pi.php'? To further elaborate, I am getting the following reoccurring error, this time after trying to login to my login page: SQLSTATE[42S22]: Column not found: 1054 Unknown column 'u.book_id' in 'field list'' in... I suspect the problem resides at a MySQL table used for my login, of which has a primary key called id Marc B originally solved an identical problem for me in this post http://stackoverflow.com/questions/2702229/doctrine-codeigniter-mysql-crud-errors when I had the same problem with a different table within the same database. Following his suggestion, I changed the default primary key located at system/application/plugins/doctrine_pi.php from 'id' to 'book_id': <?php // system/application/plugins/doctrine_pi.php ... // set the default primary key to be named 'id', integer, 4 bytes Doctrine_Manager::getInstance()->setAttribute( Doctrine::ATTR_DEFAULT_IDENTIFIER_OPTIONS, array('name' => 'book_id', 'type' => 'integer', 'length' => 4)); and that solved my previous problem. However, my login page stopped working. So what is the safe thing to do? Change all of my primary keys to 'id' (will that solve the problem without causing some other problem I am not aware of). Or should I add some lines of code in doctrine_pi.php?

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  • Alternatives to static methods on interfaces for enforcing consistency

    - by jayshao
    In Java, I'd like to be able to define marker interfaces, that forced implementations to provide static methods. For example, for simple text-serialization/deserialization I'd like to be able to define an interface that looked something like this: public interface TextTransformable<T>{ public static T fromText(String text); public String toText(); Since interfaces in Java can't contain static methods though (as noted in a number of other posts/threads: here, here, and here this code doesn't work. What I'm looking for however is some reasonable paradigm to express the same intent, namely symmetric methods, one of which is static, and enforced by the compiler. Right now the best we can come up with is some kind of static factory object or generic factory, neither of which is really satisfactory. Note: in our case our primary use-case is we have many, many "value-object" types - enums, or other objects that have a limited number of values, typically carry no state beyond their value, and which we parse/de-parse thousands of time a second, so actually do care about reusing instances (like Float, Integer, etc.) and its impact on memory consumption/g.c. Any thoughts?

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  • What is the "Apple" key and what key is it that is depicted as part of an upper case X?

    - by Marnix A. van Ammers
    I read in some answers about using the "Apple" + "Space bar" keys. Which is the "Apple" key? Also, I see in my Mac OS X Safari menu bar that to open the download window I can use a 3 key combination. The last of the 3 keys are the Command key (depicted with a clover leaf symbol) and the 'L' key. The first key is the one I don't see anywhere. It is depicted by a symbol that looks to me like an upper case 'X' with most of the forward slash part removed. What key is that? OK, just discovered by trial and error that it must be a symbol for the "option" key. What is that symbol called and why is it not on the keyboard?

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  • Changing the passphrase of a private key in Windows

    - by janos
    I have a private key in Windows, created by puttygen.exe. I used default options to save it, the tool automatically gave it a .ppk extension, and it looks like this: PuTTY-User-Key-File-2: ssh-rsa Encryption: none Comment: rsa-key-20130627 Public-Lines: 4 AAAAB3NzaC1yc2EAAAABJQAAAIBnvvAhyMs4rdlQd4OdajDw4jIPi6vIjrWjt4l4 5C3wHOSxyQQdtSA8XT3K0rSBnNtZRJTb5mfix67qQe3pHCTMSNsYIaBi8xQJHZRa RxdY+1VtGnSlEma8KO2We9eDNCGiwrRTUzqvTiGCnzU0pF1MXxu3ObISJcpqv+sQ 1GB0cw== Private-Lines: 8 AAAA.......... Private-MAC: XXXXXXXXX Now I need to change the passphrase, and reading from the docs it seemed simple enough: puttygen.exe -P key.ppk But this pops up a window with this error: PuTTYgen Error: Couldn't load private key (unable to open file) I also tried to change the passphrase using ssh-keygen that comes with Git Bash: ssh-keygen.exe -p -f key.ppk It asks for my old passphrase, but then it gives me the error Bad passphrase. Which is not true, because I can add the key in pageant.exe, and I am not mistyping the passphrase... Anything else I can try to change or drop the passphrase?

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  • drawbacks of storing all ''things' in a central table

    - by naiquevin
    Hi, I am not sure if there is a term to describe this, but I have observed that content management systems store all kinds of data in a single table with their bare minimum properties while the meta data is stored in another table in form of key value pairs. for eg. everything (blog posts, pages, images, events etc) is stored in one table and considered as a post. I understand that this allows for abstraction and easy extensibility we are considering designing our new project this way. It is not exactly a CMS but we plan to keep adding modules to it in stages. Lets say initially there will be only posts and images on which comments can be posted. Later on we might add videos which will also have the commenting feature. what are the drawbacks of this approach ? and will it work for a requirement like ours ? Thanks

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  • Apple Aluminum Keyboard Via Bluetooth - Fn Key Problem

    - by Richard
    I'm connecting an Apple Bluetooth Aluminum keyboard (this one) to my Lubuntu setup using the blueman applet. The keyboard types fine, but I would like to use its fn key to change screen brightness changing, page-up (fn+ctrl+down), page-down (fn+ctrl+up), et cetera. Right now the fn key doesn't seem to work. When I use xev, I don't see anything happen when I press fn. Does the keyboard not send this to the computer at all? Do I need to configure blueman's "Input Service" setting to make this an Apple (rather than a generic) keyboard? (It's not obvious how to do this.) Is xev just not showing the fn key? Where in this stack of software do I need to make a change to achieve the desired behaviour? Thanks!

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  • Cannot Unbind Super Key from Unity

    - by Tom Thorogood
    Due to a graphics card compatibility issue using CrunchBang, I was told that my best option would be to move to 12.04 LTS. I'm trying to get everything configured and personalized the way I'm used to things, but am having some issues with unbinding default Unity shortcuts. I'm used to having all my shortcuts routed through the super key (T for Terminal, W for Web, Up for increased opacity, and so on). I've followed instructions to install compizconfig-settings-manager, and did an advanced search for all keyboard shortcuts binding to the super key, including the Unity shortcuts, but Unity still seems to listen for that keypress, and thus neither compiz nor the keybindings set up in system prefs - keyboard receive the commands I give them. (I did try also to simply change the unity launcher key instead of disabling it as shown below -- neither worked)

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  • Can't connect to a remote server with Nautilus and a private key

    - by Desmond Hume
    The remote server requires a private key and passphrase for authentication. I tried putting username@server in the "Server" field and leaving "User name" and "Password" fields blank, putting the passphrase in the "Password" field, but it still says "Permission denied" and it doesn't ask for the private key at any point. I also tried ssh-add path/to/privatekey, but it says "Could not open a connection to your authentication agent.", however I'm not sure if ssh-add is even relevant. I can ssh into the server from the terminal just fine with the key/passphrase.

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  • Acting as though the laptop Fn key is pressed

    - by Matt
    I have a Fujitsu laptop and all was working fine until I ended teamviewer. On the keyboard it has a numberpad on some of the letters which you press the Fn button to use. The system is acting like I have the Fn key pressed and I get numbers shown when it should be letters. If I press the Fn key the numbers go to letters. The Fn key is not stuck down. Is there a way to reset keyboard settings or a known fix. The operating system is Ubuntu 11.04 Natty.

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  • How to change Shift + <Keypad Key> behavior ?

    - by LeGEC
    I am used to use the numeric keypad for navigation (e.g. : [KP7] - Start, [KP1] - End, [KP4] - Left, etc... ). I am also used to use it for selection (e.g. : Shift+[KP7] - Select from cursor position to beginning of line, Shift+[KP1] - Select from cursor position to end of line, etc...) With the keyboard configuration installed with Ubuntu, though, Shift+[KP7] prints the character "7", Shift+[KP1] prints "1", etc... How can I change this so that Shift+[KP-key] is not mapped to [key], but to Shift+[KP-key] ?

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  • How is intermediate data organized in MapReduce?

    - by Pedro Cattori
    From what I understand, each mapper outputs an intermediate file. The intermediate data (data contained in each intermediate file) is then sorted by key. Then, a reducer is assigned a key by the master. The reducer reads from the intermediate file containing the key and then calls reduce using the data it has read. But in detail, how is the intermediate data organized? Can a data corresponding to a key be held in multiple intermediate files? What happens when there is too much data corresponding to one key to be held by a single file? In short, how do intermediate partitions differ from intermediate files and how are these differences dealt with in the implementation?

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