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• Database structure - is mySQL the right choice?

  - by Industrial

  Hi everyone, We are currently planning the database structure of a quite complex e-commerce web app that has flexibility as it's main cornerstone. Our app features a large amount of data (products) and we have run into a slight headache trying to keep performance high without compromizing normalization rules in the database, or leaving our highly beloved flexibility concept behind when integrating product options (also widely known as product attributes or parameters). Based on various references and sources available, we have made up lists on pros and cons of all major and well known database patterns to solve this. After comparing these, we have come up with two final alternatives: EAV (Entity-attribute-value model) : Pros: Database is used for all sorting. Cons: All related queries will include a number of joins between multiple tables in order to complete the collection of data. SLOB (Serialized LOB, also known as Facade?) : Pros: Very flexible. Keeping the number of necessary joins low compared to a EAV design pattern. Easy to update/add/remove data from each product. Cons: All sorting will be done by the application instead of the database. Will use lots of performance (memory?) when big datasets is processed by a large number of users. Our main questions: Which pattern/structure would you use, or maybe even a different solution? Is there better databases besides mySQL available nowadays to accomplish what we want? Thanks a lot! Reference: http://stackoverflow.com/questions/695752/product-table-many-kinds-of-product-each-product-has-many-parameters

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• Java: volatile guarantees and out-of-order execution

  - by WizardOfOdds

  Note that this question is solely about the volatile keyword and the volatile guarantees: it is not about the synchronized keyword (so please don't answer "you must use synchronize" for I don't have any issue to solve: I simply want to understand the volatile guarantees (or lack of guarantees) regarding out-of-order execution). Say we have an object containing two volatile String references that are initialized to null by the constructor and that we have only one way to modify the two String: by calling setBoth(...) and that we can only set their references afterwards to non-null reference (only the constructor is allowed to set them to null). For example (it's just an example, there's no question yet): public class SO { private volatile String a; private volatile String b; public SO() { a = null; b = null; } public void setBoth( @NotNull final String one, @NotNull final String two ) { a = one; b = two; } public String getA() { return a; } public String getB() { return b; } } In setBoth(...), the line assigning the non-null parameter "a" appears before the line assigning the non-null parameter "b". Then if I do this (once again, there's no question, the question is coming next): if ( so.getB() != null ) { System.out.println( so.getA().length ); } Am I correct in my understanding that due to out-of-order execution I can get a NullPointerException? In other words: there's no guarantee that because I read a non-null "b" I'll read a non-null "a"? Because due to out-of-order (multi)processor and the way volatile works "b" could be assigned before "a"? volatile guarantees that reads subsequent to a write shall always see the last written value, but here there's an out-of-order "issue" right? (once again, the "issue" is made on purpose to try to understand the semantics of the volatile keyword and the Java Memory Model, not to solve a problem).

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• Rails: constraint violation on create but not on update

  - by justinbach

  Note: This is a "railsier" (and more succinct) version of this question, which was getting a little long. I'm getting Rails behavior on a production server that I can't replicate on the development server. The codebases are identical save for credentials and caching settings, and both are powered by Oracle 10g databases with identical schema (but different data). My Rails application contains a user model, which has_one registration; registration in turn has_and_belongs_to_many company_ownerships through a registration_ownerships table. Upon registering, users fill out data pertinent to all three models, including a series of checkboxes indicating what registration_ownerships might apply to their account. On the dev server, the registration process is seamless, no matter what data is entered. On production, however, if users check off any of the company ownership fields before submitting their registration, Oracle complains about a constraint violation on the primary key of the company_ownerships table (which is a two-field key based on company_ownership_id and registration_id) and users get the standard Rails 500 error screen. In every case, I've verified that no conflicting record on these two fields exists in the production database, so I don't know why the constraint is getting violated. To further confuse things, if a user registers without listing any ownerships and later goes back and modifies their account to reflect ownership data (which is done through the same interface), the application happily complies with their request and Oracle is well-behaved (this is both on production and dev). I've spent the past couple days trying to figure out what might be causing this problem and am reaching the end of my wits. Any advice would be greatly appreciated!

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• Uncaught TypeError: Object [object Object] has no method 'onAdded'

  - by user3604227

  I am using ExtJS4 with Java servlets. I am following the MVC architecture for ExtJS. I am trying a simple example of displaying a border layout but it doesnt work and I get the following error in ext-all.js in the javascript console: Uncaught TypeError: Object [object Object] has no method 'onAdded' Here is my code: app.js Ext.Loader.setConfig({ enabled : true }); Ext.application({ name : 'IN', appFolder : 'app', controllers : [ 'Items' ], launch : function() { console.log('in LAUNCH-appjs'); Ext.create('Ext.container.Viewport', { items : [ { xtype : 'borderlyt' } ] }); } }); Items.js (controller) Ext.define('IN.controller.Items', { extend : 'Ext.app.Controller', views : [ 'item.Border' ], init : function() { this.control({ 'viewport > panel' : { render : this.onPanelRendered } }); }, onPanelRendered : function() { console.log('The panel was rendered'); } }); Border.js (view) Ext.define('IN.view.item.Border',{extend : 'Ext.layout.container.Border', alias : 'widget.borderlyt', title : 'Border layout' , autoShow : true, renderTo : Ext.getBody(), defaults : { split : true, layout : 'border', autoScroll : true, height : 800, width : 500 }, items : [ { region : 'north', html : "Header here..", id : 'mainHeader' }, { region : 'west', width : 140, html : "Its West..", }, { region : 'south', html : "This is my temp footer content", height : 30, margins : '0 5 5 5', bodyPadding : 2, id : 'mainFooter' }, { id : 'mainContent', collapsible : false, region : 'center', margins : '5', border : true, } ] }); The folder structure for the Webcontent is as follows: WebContent app controller Items.js model store view item Border.js ext_js resources src ext_all.js index.html app.js Can someone help me resolve this error? Thanks in advance

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• iPhone OS: Why is my managedModelObject not complying with Key Value Coding?

  - by nickthedude

  Ok so I'm trying to build this stat tracker for my app and I have built a data model object called statTracker that keeps track of all the stuff I want it to. I can set and retrieve values using the selectors, but if I try and use KVC (ie setValue: forKey: ) everything goes bad and says my StatTracker class is not KVC compliant: valueForUndefinedKey:]: the entity StatTracker is not key value coding-compliant for the key "timesLauched".' 2010-05-18 15:55:08.573 here's the code that is triggering it: NSArray *statTrackerArray = [[NSArray alloc] init]; statTrackerArray = [[CoreDataSingleton sharedCoreDataSingleton] getStatTracker]; NSNumber *number1 = [[NSNumber alloc] init]; number1 = [NSNumber numberWithInt:(1 + [[(StatTracker *)[statTrackerArray objectAtIndex:0] valueForKey:@"timesLauched"] intValue])]; [(StatTracker *)[statTrackerArray objectAtIndex:0] setValue:number1 forKey:@"timesLaunched" ]; NSError *error; if (![[[CoreDataSingleton sharedCoreDataSingleton] managedObjectContext] save:&error]) { NSLog(@"error writing to db"); } Not sure if this is enough code for you folks let me know what you need if you do need more. This would be so sweet if I could use KVC because I could then abstract all this stat tracking stuff into a single method call with a string argument for the value in question. At least that is what I hope to accomplish here. I'm actually now understanding the power of KVC but now I'm just trying to figure out how to make it work. Thanks! Nick

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• How to avoid multiple, unused has_many associations when using multiple models for the same entity (

  - by mikep

  Hello, I'm looking for a nice, Ruby/Rails-esque solution for something. I'm trying to split up some data using multiple tables, rather than just using one gigantic table. My reasoning is pretty much to try and avoid the performance drop that would come with having a big table. So, rather than have one table called books, I have multiple tables: books1, books2, books3, etc. (I know that I could use a partition, but, for now, I've decided to go the 'multiple tables' route.) Each user has their books placed into a specific table. The actual book table is chosen when the user is created, and all of their books go into the same table. The goal is to try and keep each table pretty much even -- but that's a different issue. One thing I don't particularly want to have is a bunch of unused associations in the User class. Right now, it looks like I'd have to do the following: class User < ActiveRecord::Base has_many :books1, :books2, :books3, :books4, :books5 end class Books1 < ActiveRecord::Base belongs_to :user end class Books2 < ActiveRecord::Base belongs_to :user end First off, for each specific user, only one of the book tables would be usable/applicable, since all of a user's books are stored in the same table. So, only one of the associations would be in use at any time and any other has_many :bookX association that was loaded would be a waste. I don't really know Ruby/Rails does internally with all of those has_many associations though, so maybe it's not so bad. But right now I'm thinking that it's really wasteful, and that there may just be a better, more efficient way of doing this. Is there's some sort of special Ruby/Rails methodology that could be applied here to avoid having to have all of those has_many associations? Also, does anyone have any advice on how to abstract the fact that there's multiple book tables behind a single books model/class?

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• Rails nested models and data separation by scope

  - by jobrahms

  I have Teacher, Student, and Parent models that all belong to User. This is so that a Teacher can create Students and Parents that can or cannot log into the app depending on the teacher's preference. Student and Parent both accept nested attributes for User so a Student and User object can be created in the same form. All four models also belong to Studio so I can do data separation by scope. The current studio is set in application_controller.rb by looking up the current subdomain. In my students controller (all of my controllers, actually) I'm using @studio.students.new instead of Student.new, etc, to scope the new student to the correct studio, and therefore the correct subdomain. However, the nested User does not pick up the studio from its parent - it gets set to nil. I was thinking that I could do something like params[:student][:user_attributes][:studio_id] = @student.studio.id in the controller, but that would require doing attr_accessible :studio_id in User, which would be bad. How can I make sure that the nested User picks up the same scope that the Student model gets when it's created? student.rb class Student < ActiveRecord::Base belongs_to :studio belongs_to :user, :dependent => :destroy attr_accessible :user_attributes accepts_nested_attributes_for :user, :reject_if => :all_blank end students_controller.rb def create @student = @studio.students.new @student.attributes = params[:student] if @student.save redirect_to @student, :notice => "Successfully created student." else render :action => 'new' end end user.rb class User < ActiveRecord::Base belongs_to :studio accepts_nested_attributes_for :studio attr_accessible :email, :password, :password_confirmation, :remember_me, :studio_attributes devise :invitable, :database_authenticatable, :recoverable, :rememberable, :trackable end

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• Why won't the vertical margins between <p> and <hr> collapse in IE7

  - by Nicolas

  Hello all, Perhaps I am missing something, but I can't explain this from any IE bug I know of. Why in this example do the margins of the <p> and <hr> elements collapse as expected in standards compliant browsers (i.e. FF3, IE8, etc) but not in IE7 (including IE8 compatibility mode)? <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" > <head> <title>IE7 Box Model</title> <style type="text/css"> p { border: 1px solid #00f; background-color: #fefecb; margin: 20x 0 20px 0; } hr { margin: 20px 0 20px 0; } </style> </head> <body> <p> box 1 </p> <hr /> <p> box 2 </p> <hr /> <p> box 3 </p> </body> </html>

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• Which database I can used and relationship in it ??

  - by mimo-hamad

  My projece make me confused which I didn't find clear things that make me understand the required database and the relationships in it So, would a super one help me to solve it ?!! ;D this is required: 1) Model the data stored in the database (Identify the entities, roles, relationships, constraints, etc.) 2) Write the Oracle commands to create the database, find appropriate data, and populate the database 3) Write five different queries on your database, using the SELECT/FROM/WHERE construct provided in SQL. Your five queries should illustrate several different aspects of database querying, such as: a. Queries over more than one relation (by listing more than one relation in the FROM clause) b. Queries involving aggregate functions, such as SUM, COUNT, and AVG c. Queries involving complicated selects and joins d. Queries involving GROUP BY, HAVING or other similar functions. e. Queries that require the use of the DISTINCT keyword. And this the condition that we need to determine it to solve the required Q's above : 5) It is desired to develop an Internet membership club to buy products at special prices online. To join, new members must be referred by another existing member of the club. The system will keep the following information for each member: The member ID, referring member, birth date, member name, address, phone, mobile, credit card type, number and expiration date. The items are always shipped to the member's address noted in the membership application. The shipping fees will differ for each order.For each item to be requested, the member will select an item from a long list of possible items. For each item in the database, we store an item ID, an item name, description, and list price. The list price will be different from the actual sale price. The available quantity and the back-ordered quantity (the back-ordered quantity is the quantity on-order by the club from its suppliers) is also noted

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• ASP.NET Bind to IEnumerable

  - by JFoulkes

  Hi, I'm passing a the type IEnumerable to my view, and for each item I output a html.textbox to enter the details into. When I post this back to my controller, the collection is empty and I can't see why. public class Item { public Order Order { get; set; } public string Title { get; set; } public double Price { get; set; } } My Get method: public ActionResult AddItems(Order order) { Item itemOne = new Item { Order = order }; Item itemTwo = new Item { Order = order, }; IList<Item> items = new List<Item> { itemOne, itemTwo }; return View(items); } The View: <% int i = 0; foreach (var item in Model) { %> <p> <label for="Title">Item Title:</label> <%= Html.TextBox("items[" + i + "].Title") %> <%= Html.ValidationMessage("items[" + i + "].Title", "*")%> </p> <p> <label for="Price">Item Price:</label> <%= Html.TextBox("items[" + i + "].Price") %> <%= Html.ValidationMessage("items[" + i + "].Price", "*")%> </p> <% i++; } %> The POST method: [AcceptVerbs(HttpVerbs.Post)] public ActionResult AddItems(IEnumerable<Item> items) { try { return RedirectToAction("Index"); } catch { return View(); } } At the moment i just have a breakpoint on the post method to check what i'm gettin back.

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• What's the correct place to share application logic in CakePHP?

  - by Pichan

  I guess simple answer to the question would be a component. Although I agree, I feel weird having to write a component for something so specific. For example, let's say I have a table of users. When a user is created, it should form a chain reaction of events, initiating different kinds of data related to the user all around the database. I figured it would be best to avoid directly manipulating the database from different controllers and instead pack all that neatly in a method. However since some logic needs to be accesed separately, I really can't have the whole package in a single method. Instead I thought it would be logical to break it up to smaller pieces(like $userModelOrController->createNew() and $candyStorageModelOrController->createNew()) that only interact with their respective database table. Now, if the logic is put to the model, it works great until I need to use other models. Of course it's possible, but when compared to loading models in a controller, it's not that simple. It's like a Cake developer telling me "Sure, it's possible if you want to do it that way but that's not how I would do it". Then, if the logic is put to the controller, I can access other models really easy through $this->loadModel(), but that brings me back to the previously explained situation since I need to be able to continue the chain reaction indefinitely. Accessing other controllers from a controller is possible, but again there doesn't seem to be any direct way of doing so, so I'm guessing I'm still not doing it right. By using a component this problem could be solved easily, since components are available to every controller I want. But like I wrote at the beginning, it feels awkward to create a component specifically for this one task. To me, components seem more like packages of extra functionality(like the core components) and not something to share controller-specific logic. Since I'm new to this whole MVC thing, I could've completely misunderstood the concept. Once again, I would be thankful if someone pointed me to the right direction :)

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• Concrete examples of state sharing between multiple viewmodels (WPF MVVM)

  - by JohnMetta

  I have a WPF/Entity Framework (4.0) project with many objects. I'd like to build the application so that that I can have object selection state shared across viewmodels. For Example: We have Cars, Drivers, Passengers, and Cargo classes. We also have UserControls for CarList, DriverList, etc. and editor windows for CarEditor, DriverEditor, etc. Furthermore, we have viewmodels for all of these (CarListViewModel, DriverListViewModel, CargoEditorViewModel, etc). This all composes a dockable interface where the user can have multiple object lists, editors, and viewers open. What I want is a concrete code example of how to wireup multiple viewmodels so that selecting a car in the CarList will cause that car to go live in the CarEditorView, but also be selected in any other view for which the context is valid (such as a DriverByCarView- or just DriverList if there is a filter predicate). There are a number of suggestions and discussions based on this question. The two methods that seem to dominate are: 3018307: Discusses state sharing by mentioning a messaging subsystem 1159035: Discusses state sharing by using an enclosing viewmodel Is one of these approaches better than the other? Does anyone have a concrete example of either/both of these methods in the form of a write-up or small code project? I'm still learning WPF, so pointers to entry points for reading API fundamentals are appreciated, but looking at code examples is where I usually go. Thanks In case anyone is interested, here are some other similar discussions: 3816961: Discusses returning multiple viewmodels depending on object type (i.e. a collection of arbitrary types adhering to a specific interface) 1928130: Discusses whether it is a good idea to aggregate viewmodels as properties of other viewmodels (e.g. a MainWindow viewmodel composed of panel viewmodels) 1120061: Essentially discusses whether to have use a viewmodel-per-model strategy or a viewmodel-per-view-element strategy. 4244222: Discusses whether or not to nest the viewmodels when using a nested object hierarchy. 4429708: Discusses sharing collections between viewmodels directly, but doesn't go into detail. List item: Discusses managing multiple selections within a single viewmodel.

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• Get parent attribute within new child form?

  - by dannymcc

  I have a simple Rails 3 application and I am trying to create a new record that belongs to it's owner. It's working by passing the id to a hidden field in the new form of the child record. This works well and once the new child form submitted it correctly gets associated in the child/parent relationship. What I am trying to do, is lookup values form the parent within the new child form. The problem is that the child relationship is not yet created. Is there anyway I can use a .where lookup in the view? Or, is there a better way of doing this? At the moment I am passing the animal_id though to the new Claim form and it's inserted into a hidden field labelled animal_id. What I am trying to do: <%= @animal.where(:animal_id => params[:animal_id]).id %> The above would ideally get the animal ID from the soon-to-be-associated animal. Is there any sort of before_filter or anything that could take the passed params from the URL and temporarily create the relationship just for the new form view and then permanently create the relationship once the form is submitted? I've tried adding the following to my Claims controller and then called @animal.AnimalName in the view but I get NoMethodError: before_filter :find_animal protected def find_animal if params[:animal_id] Animal.find(params[:animal_id]) end end The URL of the new claim is correctly showing the animal ID so I'm not sure why it's not finding it: http://localhost:3000/claims/new?animal_id=1 The model relations are as follows: animal has_many claims animal has_one exclusion claim has_one animal exception has_one animal

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• Sorting nested set by name while keep depth integrity

  - by wb

  I'm using the nested set model that'll later be used to build a sitemap for my web site. This is my table structure. create table departments ( id int identity(0, 1) primary key , lft int , rgt int , name nvarchar(60) ); insert into departments (lft, rgt, name) values (1, 10, 'departments'); insert into departments (lft, rgt, name) values (2, 3, 'd'); insert into departments (lft, rgt, name) values (4, 9, 'a'); insert into departments (lft, rgt, name) values (5, 6, 'b'); insert into departments (lft, rgt, name) values (7, 8, 'c'); How can I sort by depth as well as name? I can do select replicate('----', count(parent.name) - 1) + ' ' + node.name , count(parent.name) - 1 as depth , node.lft from departments node , departments parent where node.lft between parent.lft and parent.rgt group by node.name, node.lft order by depth asc, node.name asc; However, that does not match children with their parent for some reason. department lft rgt --------------------------- departments 0 1 ---- a 1 4 ---- d 1 2 -------- b 2 5 -------- c 2 7 As you can see, department 'd' has department 'a's children! Thank you.

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• C++, inject additional data in a method

  - by justik

  I am adding the new modul in some large library. All methods here are implemented as static. Let mi briefly describe the simplified model: typedef std::vector<double> TData; double test ( const TData &arg ) { return arg ( 0 ) * sin ( arg ( 1 ) + ...;} double ( * p_test ) ( const TData> &arg) = &test; class A { public: static T f1 (TData &input) { .... //some computations B::f2 (p_test); } }; Inside f1() some computations are perfomed and a static method B::f2 is called. The f2 method is implemented by another author and represents some simulation algorithm (example here is siplified). class B { public: static double f2 (double ( * p_test ) ( const TData &arg ) ) { //difficult algorithm working p_test many times double res = p_test(arg); } }; The f2 method has a pointer to some weight function (here p_test). But in my case some additional parameters computed in f1 for test() methods are required double test ( const TData &arg, const TData &arg2, char *arg3.... ) { } How to inject these parameters into test() (and so to f2) to avoid changing the source code of the f2 methods (that is not trivial), redesign of the library and without dirty hacks :-) ? The most simple step is to override f2 static double f2 (double ( * p_test ) ( const TData &arg ), const TData &arg2, char *arg3.... ) But what to do later? Consider, that methods are static, so there will be problems with objects. Thanks for your help.

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• Why are some classes created on the fly and others aren't in CakePHP 1.2.7?

  - by JoseMarmolejos

  I have the following model classes: class User extends AppModel { var $name= 'User'; var $belongsTo=array('SellerType' => array('className' => 'SellerType'), 'State' => array('className' => 'State'), 'Country' => array('className' => 'Country'), 'AdvertMethod' => array('className' => 'AdvertMethod'), 'UserType' => array('className' => 'UserType')); var $hasMany = array('UserQuery' => array('className' => 'UserQuery'));} And: class UserQuery extends AppModel { var $name = 'UserQuery'; var $belongsTo = array('User', 'ResidenceType', 'HomeType');} Everything works fine with the user class and all its associations, but the UserQuery class is being completely ignored by the orm (table name user_queries and the generated queries do cast it as UserQuery. Another weird thing is that if I delete the code inside the User class I get an error, but if I do the same for the UserQuery class I get no errors. So my question is why does cakephp generate a class on the fly for the UserQuery and ignores my class, and why doesn't it generate a class on the fly for the User as well ?

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• CSS 100% height with padding/margin

  - by Toji

  This has been driving me crazy for a couple of days now, but in reality it's a problem that I've hit off and on for the last few years: With HTML/CSS how can I make an element that has a width and/or height that is 100% of it's parent element and still has proper padding or margins? By "proper" I mean that if my parent element is 200px tall and I specify 100% height with 5px padding I would expect that I should get a 190px high element with 5px "border" on all sides, nicely centered in the parent element. Now, I know that that's not how the standard box model specifies it should work (although I'd like to know why, exactly...), so the obvious answer doesn't work: #myDiv { width: 100% height: 100%; padding: 5px; } But it would seem to me that there must be SOME way of reliably producing this effect for a parent of arbitrary size. Does anyone know of a way of accomplishing this (seemingly simple) task? Oh, and for the record I'm not terribly interested in IE compatibility so that should (hopefully) make things a bit easier. EDIT: Since an example was asked for, here's the simplest one I can think of: <html style="height: 100%"> <body style="height: 100%"> <div style="background-color: black; height: 100%; padding: 25px"></div> </body> </html> The challenge is then to get the black box to show up with a 25 pixel padding on all edges without the page growing big enough to require scrollbars.

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• Short Season, Long Models - Dealing with Seasonality

  - by Michel Adar

  Accounting for seasonality presents a challenge for the accurate prediction of events. Examples of seasonality include: ·         Boxed cosmetics sets are more popular during Christmas. They sell at other times of the year, but they rise higher than other products during the holiday season. ·         Interest in a promotion rises around the time advertising on TV airs ·         Interest in the Sports section of a newspaper rises when there is a big football match There are several ways of dealing with seasonality in predictions. Time Windows If the length of the model time windows is short enough relative to the seasonality effect, then the models will see only seasonal data, and therefore will be accurate in their predictions. For example, a model with a weekly time window may be quick enough to adapt during the holiday season. In order for time windows to be useful in dealing with seasonality it is necessary that: The time window is significantly shorter than the season changes There is enough volume of data in the short time windows to produce an accurate model An additional issue to consider is that sometimes the season may have an abrupt end, for example the day after Christmas. Input Data If available, it is possible to include the seasonality effect in the input data for the model. For example the customer record may include a list of all the promotions advertised in the area of residence. A model with these inputs will have to learn the effect of the input. It is possible to learn it specific to the promotion – and by the way learn about inter-promotion cross feeding – by leaving the list of ads as it is; or it is possible to learn the general effect by having a flag that indicates if the promotion is being advertised. For inputs to properly represent the effect in the model it is necessary that: The model sees enough events with the input present. For example, by virtue of the model lifetime (or time window) being long enough to see several “seasons” or by having enough volume for the model to learn seasonality quickly. Proportional Frequency If we create a model that ignores seasonality it is possible to use that model to predict how the specific person likelihood differs from average. If we have a divergence from average then we can transfer that divergence proportionally to the observed frequency at the time of the prediction. Definitions: Ft = trailing average frequency of the event at time “t”. The average is done over a suitable period of to achieve a statistical significant estimate. F = average frequency as seen by the model. L = likelihood predicted by the model for a specific person Lt = predicted likelihood proportionally scaled for time “t”. If the model is good at predicting deviation from average, and this holds over the interesting range of seasons, then we can estimate Lt as: Lt = L * (Ft / F) Considering that: L = (L – F) + F Substituting we get: Lt = [(L – F) + F] * (Ft / F) Which simplifies to: (i)                  Lt = (L – F) * (Ft / F)  +  Ft This latest expression can be understood as “The adjusted likelihood at time t is the average likelihood at time t plus the effect from the model, which is calculated as the difference from average time the proportion of frequencies”. The formula above assumes a linear translation of the proportion. It is possible to generalize the formula using a factor which we will call “a” as follows: (ii)                Lt = (L – F) * (Ft / F) * a  +  Ft It is also possible to use a formula that does not scale the difference, like: (iii)               Lt = (L – F) * a  +  Ft While these formulas seem reasonable, they should be taken as hypothesis to be proven with empirical data. A theoretical analysis provides the following insights: The Cumulative Gains Chart (lift) should stay the same, as at any given time the order of the likelihood for different customers is preserved If F is equal to Ft then the formula reverts to “L” If (Ft = 0) then Lt in (i) and (ii) is 0 It is possible for Lt to be above 1. If it is desired to avoid going over 1, for relatively high base frequencies it is possible to use a relative interpretation of the multiplicative factor. For example, if we say that Y is twice as likely as X, then we can interpret this sentence as: If X is 3%, then Y is 6% If X is 11%, then Y is 22% If X is 70%, then Y is 85% - in this case we interpret “twice as likely” as “half as likely to not happen” Applying this reasoning to (i) for example we would get: If (L < F) or (Ft < (1 / ((L/F) + 1)) Then  Lt = L * (Ft / F) Else Lt = 1 – (F / L) + (Ft * F / L)  

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• getJSON not working if the mvc model view controller has a parameter

  - by Paul

  I'm having an issue with a callback. I'm not even getting an error in Firebug. If I alert before and after the getjson call both alerts show but the getjson call doesn't fire. public ActionResult TestPage() { return View(); } public ActionResult LoadMapLonLats(int mapId) { //some code return Json(_myMaps); } $("#Search").click(function() { $.getJSON("LoadMapLonLats", { mapId: 73 }, loadDbMap); }); function loadDbMap(maps) { alert('m'); $.each(maps, function(i) { alert(maps[i]); }); } As long as I leave TestPage without a parameter is works. If I add a parameter to TestPage(int id) then the call back to LoadMapLonLats doesn't work. Seems odd. Of course TestPage is the page I'm loading so I need to do some work here before rendering the page. Not sure why adding a parameter to the view would break the callback to another function. //this breaks he callback to LoadMapLonLats public ActionResult TestPage(int id) { return View(); } Any ideas? Seems like this may be related, if not sorry I can post a new thread.

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• Use Html.RadioButtonFor and Html.LabelFor for the same Model but different values

  - by Marc

  I have this Razor Template <table> <tr> <td>@Html.RadioButtonFor(i => i.Value, "1")</td> <td>@Html.LabelFor(i => i.Value, "true")</td> </tr> <tr> <td>@Html.RadioButtonFor(i => i.Value, "0")</td> <td>@Html.LabelFor(i => i.Value, "false")</td> </tr> </table> That gives me this HTML <table> <tr> <td><input id="Items_1__Value" name="Items[1].Value" type="radio" value="1" /></td> <td><label for="Items_1__Value">true</label></td> </tr> <tr> <td><input checked="checked" id="Items_1__Value" name="Items[1].Value" type="radio" value="0" /></td> <td><label for="Items_1__Value">false</label></td> </tr> </table> So I have the ID Items_1__Value twice which is - of course - not good and does not work in a browser when I click on the second label "false" the first radio will be activated. I know I could add an own Id at RadioButtonFor and refer to that with my label, but that's not pretty good, is it? Especially because I'm in a loop and cannot just use the name "value" with an added number, that would be end up in multiple Dom Ids in my final HTML markup as well. Shouldn't be a good solution for this?

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• MVVM- Trigger Storyboard in the View Model in Silverlight

  - by user275561

  I have a couple of Storyboards in my view that I would like to trigger from the ViewModel if possible. Is there a simple way or elegant way of doing this. Here is what I am trying to do. Person Clicks on a Button--RelayCommand (In the ViewModel), the Relay Command should then play the storyboard. Also one more thing, I would like to also trigger the storyboard animation by itself in the ViewModel without any interaction. <i:Interaction.Triggers> <i:EventTrigger EventName="MouseLeftButtonDown"> <cmd:EventToCommand Command="{Binding ButtonPress}" CommandParameterValue="RedButtonLight"> </cmd:EventToCommand> </i:EventTrigger> </i:Interaction.Triggers>

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• ASP.NET MVC 2 JQuery POST not displaying the model state errors

  - by Oshan

  Hello, I have been using asp.net mvc for a bit (but I'm still a beginer). I want to have the ability to update two views as a result of a jquery postback. Basically I have a list and a details view. The details view is presented using a jquery popup (using jquery-UI popup). I only want to update the list if the details save is successful (i.e. there are no validation errors on the details view). However, if there are any validation errros in the details view, I want to update the details view so that the user sees the validation errors. so I thought in my controller, I return a JsonResult instead of a View. [HttpPost] public ActionResult SavePersonInfo(Person p) { if(ModelState.Valid) { return View("PersonList"); } return Json({Error = true, View = PartialView("PersonDetails", p)}); } As you can see if there are no errors I return the person list view, but if there are any validation errors, I have return the details view. The reason that I'm returning a JsonResult is I need to tell my view there is an error so that the view (jquery) knows which section to update (as in whether to update the person list 'div' or the popup dialog 'div'). So, in my view, the jquery is as follows (please assume that there is a form for entering in the person details and "SubmitPersonForm();" function is called upon clicking on the "Save" button): <script type="text/javascript> $('#btnSave').click(function (event) { onBegin(); $.ajax( { type: "POST", url: "/Person/Save", data: $('form').serialize(), success: function (result) { if(result.Error) { $('#dvDetails').html($(result).View)); } else { $('#dvPersonList').html($result); } } }); }); </script> So the problem that I have now, is that when there is a validation error, I do see the correct, 'div' being updated, but I lose the asp.net mvc validation messages. I do not see any validation errors in red, as if ASP.NET MVC is completely ignored them. However, my ModelState does have those errros, just not displayed in the details view. I do have valication summary and Html.ValidationFor(m = ...) statements put in my details view. Could someone tell me why I'm not seeing the validation errors? although I'm using a JSonResult, I do use the right property which is a valid view when I render the 'dvDetails'. Am I doing something that I'm not suppose to in asp.net mvc? Btw I'm using asp.net mvc2 RC with Visual Studio 2010 RC. Thank you.

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• Difference between the Repository Pattern and the View Model Pattern

  - by Mark Sayewich

  I am trying to create a site using the ASP MVC Framework. Some of the documentation use the IRepository pattern to abstract the information being sent to the view for rendering, while others recommend using a ViewModel (as in MVVC). What is the difference? Aren't these the same concept? Thanks in advance

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• Entity Data Model & DataGridView - Creating new objects

  - by AcousticBoom

  I'm pretty new to the EDM, so bear with me. I have a windows form that has a DataGridView on it that's bound from the EDM I created. I figured out how to update my changes fine, but it's when the user creates a new row that I'm having a problem. I tried numerous ways and many google searches, but came up with nothing so far. Here's how the data is loaded: Dim boilerID As Integer = DirectCast(ddlBoiler.SelectedValue, Integer) Dim countryID As Integer = DirectCast(ddlCountry.SelectedValue, Integer) Dim ratings = From r In _Context.Rating _ Where r.Boiler.Boiler_ID = boilerID _ And r.Country.Country_ID = countryID _ Order By r.Sequence _ Select r RatingBindingSource.DataSource = ratings.ToList() Also, all I'm doing to save the information right now is the following: Private Sub btnSave_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSave.Click _Context.SaveChanges() End Sub I want the user to be able to use the grid's "new row" feature to add new items to the database instead of having to click a button and open a new dialog. How would this be accomplished? I can include some of the methods i tried for adding new items if anyone needs to see. Thanks!

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• wpf toolkit (Feb 2010) datagrid with MVVM - style reveals name of view model on 'spare column'

  - by Andy Clarke

  Hi, I've just updated my app with the latest WPF toolkit and I've now got an issue with my styling. When I bind some data with, for example, two columns to the grid, the spare area at the right shows the name of the ViewModel in the header. I can understand why, because the data grids data context is the ViewModel and I'm defining my header style as follows ... <WpfToolkit:DataGridHeaderBorder <Border BorderBrush="Blue" BorderThickness="0,1,0,0"> <TextBlock Text="{Binding}" Margin="4,0,4,0" /> </Border> </WpfToolkit:DataGridHeaderBorder> Do I now need a separate style for the 'spare column' or something? Can anyone assist please? Cheers, Andy

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