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• Web user expectations

  - by Ash

  When designing a good Web GUI what expectations can we expect from an end user? I've come up with the following, but I wonder if there are any others which can suggest.. If I click on a hyperlink it will take me to another page/part of this page If I tick/untick a checkbox it might alter the page state (enable/disable elements) If I click on a button I expect it to do something to data. If I click on a button I expect something to happen immediately (either to the current page, or for me to be taken to another page) If I have clicked on a hyperlink and it has taken me to another page, I expect to be able to use the Back button to get back to the previous page in a state similar to that which I left it in If I change something in a form, I can change it back to its previous value if necessary Unless I click on the 'Submit' button nothing should happen to my data. If I bookmark/favourite a page then it should show the same related data each time I visit it If text is underlined and looks like a link, it should be a link and act as one The reasoning behind this question is more a 'UI from hell' one. For example I have come across pages which checking a tickbox next to a record will delete it, straight away, via ajax. To me that just seems wrong, a checkbox is a toggle - something which a delete operation definitely isn't!

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• Data access pattern

  - by andlju

  I need some advice on what kind of pattern(s) I should use for pushing/pulling data into my application. I'm writing a rule-engine that needs to hold quite a large amount of data in-memory in order to be efficient enough. I have some rather conflicting requirements; It is not acceptable for the engine to always have to wait for a full pre-load of all data before it is functional. Only fetching and caching data on-demand will lead to the engine taking too long before it is running quickly enough. An external event can trigger the need for specific parts of the data to be reloaded. Basically, I think I need a combination of pushing and pulling data into the application. A simplified version of my current "pattern" looks like this (in psuedo-C# written in notepad): // This interface is implemented by all classes that needs the data interface IDataSubscriber { void RegisterData(Entity data); } // This interface is implemented by the data access class interface IDataProvider { void EnsureLoaded(Key dataKey); void RegisterSubscriber(IDataSubscriber subscriber); } class MyClassThatNeedsData : IDataSubscriber { IDataProvider _provider; MyClassThatNeedsData(IDataProvider provider) { _provider = provider; _provider.RegisterSubscriber(this); } public void RegisterData(Entity data) { // Save data for later StoreDataInCache(data); } void UseData(Key key) { // Make sure that the data has been stored in cache _provider.EnsureLoaded(key); Entity data = GetDataFromCache(key); } } class MyDataProvider : IDataProvider { List<IDataSubscriber> _subscribers; // Make sure that the data for key has been loaded to all subscribers public void EnsureLoaded(Key key) { if (HasKeyBeenMarkedAsLoaded(key)) return; PublishDataToSubscribers(key); MarkKeyAsLoaded(key); } // Force all subscribers to get a new version of the data for key public void ForceReload(Key key) { PublishDataToSubscribers(key); MarkKeyAsLoaded(key); } void PublishDataToSubscribers(Key key) { Entity data = FetchDataFromStore(key); foreach(var subscriber in _subscribers) { subscriber.RegisterData(data); } } } // This class will be spun off on startup and should make sure that all data is // preloaded as quickly as possible class MyPreloadingThread { IDataProvider _provider; MyPreloadingThread(IDataProvider provider) { _provider = provider; } void RunInBackground() { IEnumerable<Key> allKeys = GetAllKeys(); foreach(var key in allKeys) { _provider.EnsureLoaded(key); } } } I have a feeling though that this is not necessarily the best way of doing this.. Just the fact that explaining it seems to take two pages feels like an indication.. Any ideas? Any patterns out there I should have a look at?

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• Objective-C partial implementation of classes in separate files

  - by Aran Mulholland

  I am using core data and am generating classes from my data model. I implement custom methods in these classes, however when i regenerate i generate over the top so i end up copying and pasting a bit. What i would like to do is split my implementation files ('.m') so i can have one header file with multiple '.m' files. then i can keep my custom methods in one and not have to worry about erasing them when i regenerate. I use this technique in .NET a lot with its partial keyword. Is there anything similar in objective-C

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• Graph navigation problem

  - by affan

  I have graph of components and relation between them. User open graph and want to navigate through the graph base on his choice. He start with root node and click expand button which reveal new component that is related to current component. The problem is with when use decide to collapse a node. I have to choose a sub-tree to hide and at same time leave graph in consistent state so that there is no expanded node with missing relation to another node in graph. Now in case of cyclic/loop between component i have difficult of choosing sub-tree. For simplicity i choose the order in which they were expanded. So if a A expand into B and C collapse A will hide the nodes and edge that it has created. Now consider flowing scenario. [-] mean expanded state and [+] mean not yet expanded. A is expanded to reveal B and C. And then B is expanded to reveal D. C is expanded which create a link between C and exiting node D and also create node E. Now user decide to collapse B. Since by order of expansion D is child of B it will collapse and hide D. This leave graph in inconsistent state as C is expanded with edge to D but D is not anymore there if i remove CD edge it will still be inconsistent. If i collapse C. And E is again a cyclic link e.g to B will produce the same problem. /-----B[-]-----\ A[-] D[+] \-----C[-]-----/ \ E[+] So guys any idea how can i solve this problem. User need to navigate through graph and should be able to collapse but i am stuck with problem of cyclic nodes in which case any of node in loop if collapse will leave graph in inconsistent state.

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• Create inherited class from base class

  - by Raj

  public class Car { private string make; private string model; public Car(string make, string model) { this.make = make; this.model = model; } public virtual void Display() { Console.WriteLine("Make: {0}", make); Console.WriteLine("Model: {0}", model); } public string Make { get{return make;} set{make = value;} } public string Model { get{return model;} set{model = value;} } } public class SuperCar:Car { private Car car; private int horsePower; public SuperCar(Car car) { this.car = car; } public int HorsePower { get{return horsePower;} set{horsepower = value;} } public override void Display() { base.Display(); Console.WriteLine("I am a super car"); } When I do something like Car myCar = new Car("Porsche", "911"); SuperCar mySupcar = new SuperCar(myCar); mySupcar.Display(); I only get "I am a supercar" but not the properties of my base class. Should I explicitly assign the properties of my base class in the SuperCar constructor? In fact I'm trying Decorator pattern where I want a class to add behaviour to a base class.

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• What are some funny error pages websites have?

  - by Dean

  This question is along the same lines as What are some funny loading statements to keep my users amused, I want screenshots of all the coolest "error" pages site's throw up when something's broken. I know pandora.com talks about a panda ravaging it's way through the office, twitter's has the little birds floating around or something, sourceforge had one with some funny robots the other day. I'm sure I saw a blog once that had a bunch of them, but it's kinda hard to google "error pages". Community Wiki, of course :)

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• Business Layer Pattern on Rails? MVCL

  - by Fabiano PS

  That is a broad question, and I appreciate no short/dumb asnwers like: "Oh that is the model job, this quest is retarded (period)" PROBLEM Where I work at people created a system over 2 years for managing the manufacture process over demand in the most simplified still broad as possible, involving selling, buying, assemble, The system is coded over Ruby On Rails. The result has been changed lots of times and the result is a mess on callbacks (some are called several times), 200+ models, and fat controllers: Total bad. The QUESTION is, if there is a gem, or pattern designed to handle Rails large app logic? The logic whould be able to fully talk to models (whose only concern would be data format handling and validation) What I EXPECT is to reduce complexity from various controllers, and hard to track callbacks into files with the responsibility to handle a business operation logic. In some cases there is the need to wait for a response, in others, only validation of the input is enough and a bg process would take place. ie: -- Sell some products (need to wait the operation to finish) 1. Set a View able to get the products input 2. Controller gets the product list inputed by employee and call the logic Logic::ExecuteWithResponse('sell', 'products', :prods => @product_list_with_qtt, :when => @date, :employee => current_user() ) This Logic would handle buying order, assemble order, machine schedule, warehouse reservation, and others

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• recursive delete trigger and ON DELETE CASCADE contraints are not deleting everything

  - by bitbonk

  I have a very simple datamodel that represents a tree structure: The RootEntity is the root of such a tree, it can contain children of type ContainerEntity and of type AtomEntity. The type ContainerEntity again can contain children of type ContainerEntity and of type AtomEntity but can not contain children of type RootEntity. Children are referenced in a well known order. The DB model for this is below. My problem now is that when I delete a RootEntity I want all children to be deleted recursively. I have create foreign key with CASCADE DELETE and two delete triggers for this. But it is not deleting everything, it always leaves some items in the ContainerEntity, AtomEntity, ContainerEntity_Children and AtomEntity_Children tables. Seemling beginning with the recursionlevel of 3. CREATE TABLE RootEntity ( Id UNIQUEIDENTIFIER NOT NULL, Name VARCHAR(500) NOT NULL, CONSTRAINT PK_RootEntity PRIMARY KEY NONCLUSTERED (Id), ); CREATE TABLE ContainerEntity ( Id UNIQUEIDENTIFIER NOT NULL, Name VARCHAR(500) NOT NULL, CONSTRAINT PK_ContainerEntity PRIMARY KEY NONCLUSTERED (Id), ); CREATE TABLE AtomEntity ( Id UNIQUEIDENTIFIER NOT NULL, Name VARCHAR(500) NOT NULL, CONSTRAINT PK_AtomEntity PRIMARY KEY NONCLUSTERED (Id), ); CREATE TABLE RootEntity_Children ( ParentId UNIQUEIDENTIFIER NOT NULL, OrderIndex INT NOT NULL, ChildContainerEntityId UNIQUEIDENTIFIER NULL, ChildAtomEntityId UNIQUEIDENTIFIER NULL, ChildIsContainerEntity BIT NOT NULL, CONSTRAINT PK_RootEntity_Children PRIMARY KEY NONCLUSTERED (ParentId, OrderIndex), -- foreign key to parent RootEntity CONSTRAINT FK_RootEntiry_Children__RootEntity FOREIGN KEY (ParentId) REFERENCES RootEntity (Id) ON DELETE CASCADE, -- foreign key to referenced (child) ContainerEntity CONSTRAINT FK_RootEntiry_Children__ContainerEntity FOREIGN KEY (ChildContainerEntityId) REFERENCES ContainerEntity (Id) ON DELETE CASCADE, -- foreign key to referenced (child) AtomEntity CONSTRAINT FK_RootEntiry_Children__AtomEntity FOREIGN KEY (ChildAtomEntityId) REFERENCES AtomEntity (Id) ON DELETE CASCADE, ); CREATE TABLE ContainerEntity_Children ( ParentId UNIQUEIDENTIFIER NOT NULL, OrderIndex INT NOT NULL, ChildContainerEntityId UNIQUEIDENTIFIER NULL, ChildAtomEntityId UNIQUEIDENTIFIER NULL, ChildIsContainerEntity BIT NOT NULL, CONSTRAINT PK_ContainerEntity_Children PRIMARY KEY NONCLUSTERED (ParentId, OrderIndex), -- foreign key to parent ContainerEntity CONSTRAINT FK_ContainerEntity_Children__RootEntity FOREIGN KEY (ParentId) REFERENCES ContainerEntity (Id) ON DELETE CASCADE, -- foreign key to referenced (child) ContainerEntity CONSTRAINT FK_ContainerEntity_Children__ContainerEntity FOREIGN KEY (ChildContainerEntityId) REFERENCES ContainerEntity (Id) ON DELETE CASCADE, -- foreign key to referenced (child) AtomEntity CONSTRAINT FK_ContainerEntity_Children__AtomEntity FOREIGN KEY (ChildAtomEntityId) REFERENCES AtomEntity (Id) ON DELETE CASCADE, ); CREATE TRIGGER Delete_RootEntity_Children ON RootEntity_Children FOR DELETE AS DELETE FROM ContainerEntity WHERE Id IN (SELECT ChildContainerEntityId FROM deleted) DELETE FROM AtomEntity WHERE Id IN (SELECT ChildAtomEntityId FROM deleted) GO CREATE TRIGGER Delete_ContainerEntiy_Children ON ContainerEntity_Children FOR DELETE AS DELETE FROM ContainerEntity WHERE Id IN (SELECT ChildContainerEntityId FROM deleted) DELETE FROM AtomEntity WHERE Id IN (SELECT ChildAtomEntityId FROM deleted) GO

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• Java: initialization problem with private-final-int-value and empty constructor

  - by HH

  $ javac InitInt.java InitInt.java:7: variable right might not have been initialized InitInt(){} ^ 1 error $ cat InitInt.java import java.util.*; import java.io.*; public class InitInt { private final int right; InitInt(){} public static void main(String[] args) { // I don't want to assign any value. // just initialize it, how? InitInt test = new InitInt(); System.out.println(test.getRight()); // later assiging a value } public int getRight(){return right;} } Initialization problem with Constructor InitInt{ // Still the error, "may not be initialized" // How to initialise it? if(snippetBuilder.length()>(charwisePos+25)){ right=charwisePos+25; }else{ right=snippetBuilder.length()-1; } }

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• Relational vs. Dimensional Databases, what's the difference?

  - by grautur

  I'm trying to learn about OLAP and data warehousing, and I'm confused about the difference between relational and dimensional modeling. Is dimensional modeling basically relational modeling, but allowing for redundant/un-normalized data? For example, let's say I have historical sales data on (product, city, # sales). I understand that the following would be a relational point-of-view: Product | City | # Sales Apples, San Francisco, 400 Apples, Boston, 700 Apples, Seattle, 600 Oranges, San Francisco, 550 Oranges, Boston, 500 Oranges, Seattle, 600 While the following is a more dimensional point-of-view: Product | San Francisco | Boston | Seattle Apples, 400, 700, 600 Oranges, 550, 500, 600 But it seems like both points of view would nonetheless be implemented in an identical star schema: Fact table: Product ID, Region ID, # Sales Product dimension: Product ID, Product Name City dimension: City ID, City Name And it's not until you start adding some additional details to each dimension that the differences start popping up. For instance, if you wanted to track regions as well, a relational database would tend to have a separate region table, in order to keep everything normalized: City dimension: City ID, City Name, Region ID Region dimension: Region ID, Region Name, Region Manager, # Regional Stores While a dimensional database would allow for denormalization to keep the region data inside the city dimension, in order to make it easier to slice the data: City dimension: City ID, City Name, Region Name, Region Manager, # Regional Stores Is this correct?

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• How to build online voting system

  - by binu

  I want to do a project titled "Online Voting system" in jsp. How can I count votes in a database? MySql will be the database.

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• Which is the most memory leak safe approach.

  - by MattC

  I have a table of frequently updated information. This is presented using a container div with a div for each row, each row containing 10 divs. I am using setInterval to call a an asmx webservice that returns some json formatted information. On the success callback I call $("#myContainer").empty(); on the container div and recreate the rows and 10 nested divs for each row's columns. This page may be left to run for a whole day, so I am wary of updating the DOM like this as I have noticed that memory does rise for the browser over time (IE8). The other approach I am considering is to add an idea to the row div. When new results process each item of data, look for the corresponding row, if it exists overwrite the data in each div. If it doesn't exist (new data for example), append the row. What approaches have others used for this sort of long lived pseudo realtime information display. TIA

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• Examples of IOC/DI over Singleton

  - by Amitd

  Hi, Just started learning/reading about DI and IOC frameworks. Also I read many articles on SO and internet that say that one should prefer DI/IOC over singleton. Can anyone give/link examples of exactly how DI/IOC eliminates/solves the various issues regarding the Singleton pattern? (hopefully code and explanation for better understanding) Also given a system has already implemented Singleton pattern, how to refactor/implement DI/IOC for the same? (any examples for the same?) (Language/Framework no bars..C# would be helpful) Thanks

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• Where have you used gSOAP?

  - by cmdev

  Can you give examples how you used gSOAP and how well it was integrated in your existing architecture? Have you found development bottlenecks with gSOAP?

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• Storing varchar(max) & varbinary(max) together - Problem?

  - by Tony Basallo

  I have an app that will have entries of both varchar(max) and varbinary(max) data types. I was considering putting these both in a separate table, together, even if only one of the two will be used at any given time. The question is whether storing them together has any impact on performance. Considering that they are stored in the heap, I'm thinking that having them together will not be a problem. However, the varchar(max) column will be probably have the text in row table option set. I couldn't find any performance testing or profiling while "googling bing," probably too specific a question? The SQL Server 2008 table looks like this: Id ParentId Version VersionDate StringContent - varchar(max) BinaryContent - varbinary(max) The app will decide which of the two columns to select for when the data is queried. The string column will much used much more frequently than the binary column - will this have any impact on performance?

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• where to enlist transaction with parent child delete (repository or bll)?

  - by Caroline Showden

  My app uses a business layer which calls a repository which uses linq to sql. I have an Item class that has an enum type property and an ItemDetail property. I need to implement a delete method that: (1) always delete the Item (2) if the item.type is XYZ and the ItemDetail is not null, delete the ItemDetail as well. My question is where should this logic be housed? If I have it in my business logic which I would prefer, this involves two separate repository calls, each of which uses a separate datacontext. I would have to wrap both calls is a System.Transaction which (in sql 2005) get promoted to a distributed transaction which is not ideal. I can move it all to a single repository call and the transaction will be handled implicitly by the datacontext but feel that this is really business logic so does not belong in the repository. Thoughts? Carrie

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• To subclass or not to subclass

  - by poulenc

  I have three objects; Action, Issue and Risk. These all contain a nunber of common variables/attributes (for example: Description, title, Due date, Raised by etc.) and some specific fields (risk has probability). The question is: Should I create 3 separate classes Action, Risk and Issue each containing the repeat fields. Create a parent class "Abstract_Item" containing these fields and operations on them and then have Action, Risk and Issue subclass Abstract_Item. This would adhere to DRY principal.

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• Single value data to multiple values of data in database relation

  - by Sofiane Merah

  I have such a hard time picturing this. I just don't have the brain to do it. I have a table called reports. --------------------------------------------- | report_id | set_of_bads | field1 | field2 | --------------------------------------------- | 123 | set1 | qwe | qwe | --------------------------------------------- | 321 | 123112 | ewq | ewq | --------------------------------------------- I have another table called bads. This table contains a list of bad data. ------------------------------------- | bad_id | set_it_belongs_to | field2 | field3 | ------------------------------------- | 1 | set1 | qwe | qwe | ------------------------------------- | 2 | set1 | qee | tte | ------------------------------------- | 3 | set1 | q44w | 3qwe | ------------------------------------- | 4 | 234 | qoow | 3qwe | ------------------------------------- Now I have set the first field of every table as the primary key. My question is, how do I connect the field set_of_bads to set_it_belongs_to in the bads table. This way if I want to get the entire set of data that is set1 by calling on the reports table I can do it. Example: hey reports table.. bring up the row that has the report_id 123. Okay thank you.. Now get all the rows from bads that has the set_of_bads value from the row with the report_id 123. Thanks.

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• Making a DateTime field in SQLExpress database?

  - by Mike

  I'm putting together a simple test database to learn MVC with. I want to add a DateTime field to show when the record was CREATED. ID = int Name = Char DateCreated = (dateTime, DateTime2..?) I have a feeling that this type of DateTime capture can be done automatically - but that's all I have, a feeling. Can it be done? And if so how? While we're on the subject: if I wanted to include another field that captured the DateTime of when the record was LAST UPDATED how would I do that. I'm hoping to not do this manually. Many thanks Mike

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• Sub-Schemas in SQL Server 2005/2008

  - by Maushu

  This is a simple question yet I was unable to find any information at all about this. Is it possible to have sub-schemas in SQL Server 2005/2008? Example: Having a HR (Human Resources) schema with a sub-schema called Training (with tables related to this). It would end up like HR.Training.* where * would be the tables.

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• Best practices for managing limited client licenses/login

  - by MicSim

  I have a multi-user software solution (containing different applications, i.e. EXEs) that should allow only a limited number of concurrent users. It's designed to run in an intranet. I dont have a really good, satisfactory solution to the problem of counting the client licenses yet. The key requirements are: Multiple instances (starts) of the same application (= process) should count as only one client licence Starting different applications of the software solution should also count as only one (the same) client licence Application crash should not lead to orphaned used licences The above should work also for Terminal Server environments (all clients same IP, but different install folders) I'm looking for estabilished patterns, solutions, tips for managing used client licenses. Specific hints for the above sitaution are also welcome.

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• When should a member function have a const qualifier and when shouldn't it?

  - by SCFrench

  About six years ago, a software engineer named Harri Porten wrote this article, asking the question, "When should a member function have a const qualifier and when shouldn't it?" I found it to be the best write-up I could find of the issue, which I've been wrestling with more recently and which I think is not well covered in most discussions I've found on const correctness. Since a software information-sharing site as powerful as SO didn't exist back then, I'd like to resurrect the question here.

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• How to store a numeric value which can have other statuses in a database?

  - by Jiho Han

  I need to store a set of numbers in a database which are imported from a spreadsheet. Sometimes a number is just a number. But in other times, a value can be "missing", "N/A", or blank and these all represent different things. What would be a good approach to store these numbers in the database? Originally I only had to account for N/A. So I made it -1 as I imported them (this only works if the number can never be negative obviously). I could use other negative numbers for other statuses. However, that seems clunky to me. Should I store the numbers as string then apply conversion at use time? Should I create a matching table that stores different statuses of each value?

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• log in as a proxy for a certain user

  - by Samuel

  We have a requirement, wherein the administrative user needs to proxy in as a certain user in an environment where several users (Role: User) are managed by an administrator (Role: Admin). e.g If we have the following users in the database (admin, user1, user2, user3), we would want the admin to proxy as 'user2' and use the system in certain scenarios. Authentication in our web application is based username / password credentials, what mechanisms are available for the admin to proxy as 'user2' when he doesn't have the password for 'user2'. How can the application track such access for audit purposes to mention that 'admin' had proxied for 'user2' and performed certain actions. I am looking for suggestions on supporting this in our j2ee (jboss seam) web application.

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• DDD and Client/Server apps

  - by Christophe Herreman

  I was wondering if any of you had successfully implemented DDD in a Client/Server app and would like to share some experiences. We are currently working on a smart client in Flex and a backend in Java. On the server we have a service layer exposed to the client that offers CRUD operations amongst some other service methods. I understand that in DDD these services should be repositories and services should be used to handle use cases that do not fit inside a repository. Right now, we mimic these services on the client behind an interface and inject implementations (Webservices, RMI, etc) via an IoC container. So some questions arise: should the server expose repositories to the client or do we need to have some sort of a facade (that is able to handle security for instance) should the client implement repositories (and DDD in general?) knowing that in the client, most of the logic is view related and real business logic lives on the server. All communication with the server happens asynchronously and we have a single threaded programming model on the client. how about mapping client to server objects and vice versa? We tried DTO's but reverted back to exposing the state of our objects and mapping directly to them. I know this is considered bad practice, but it saves us an incredible amount of time) In general I think a new generation of applications is coming with the growth of Flex, Silverlight, JavaFX and I'm curious how DDD fits into this.

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