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  • What are the design principles that promote testable code? (designing testable code vs driving design through tests)

    - by bot
    Most of the projects that I work on consider development and unit testing in isolation which makes writing unit tests at a later instance a nightmare. My objective is to keep testing in mind during the high level and low level design phases itself. I want to know if there are any well defined design principles that promote testable code. One such principle that I have come to understand recently is Dependency Inversion through Dependency injection and Inversion of Control. I have read that there is something known as SOLID. I want to understand if following the SOLID principles indirectly results in code that is easily testable? If not, are there any well-defined design principles that promote testable code? I am aware that there is something known as Test Driven Development. Although, I am more interested in designing code with testing in mind during the design phase itself rather than driving design through tests. I hope this makes sense. One more question related to this topic is whether it's alright to re-factor an existing product/project and make changes to code and design for the purpose of being able to write a unit test case for each module?

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  • Accommodating hierarchical data in SQL Server 2005 database design

    - by Remnant
    Context I am fairly new to database design (=know the basics) and am grappling with how best to design my database for a project I am currently working on. In short, my database will keep a log of which employees have attended certain health and safety courses throughout the year. There are multiple types of course e.g. moving objects, fire safety, hygiene etc. In terms of my database design I need to accommodate the following: Each location can have multiple divisions Each division can have multiple departments Each department can have multiple functions Each function can have multiple job roles Each job role can have different course requirements Also note that the structure at each location may not be the same e.g. the departments within divisions are not the same across locations and the functions within departments may also differ. Edit - updated to better articulate problem Let's assume I am just looking at Location, Division and Department and I have my database as follows: LocationTable DivisionTable DepartmentTable LocationID(PK) DivisionID(PK) DepartmentID(PK) LocationName DivisionName DepartmentName There is a many-to-many relationship between Locations and Divisions and also between Departments and Divisions. Suppose I set up a 'Junction Table' as follows: Location_Division LocationID(FK) DivisionID(FK) Using Location_Division I could easily pull back the Divisions for any Location. However, suppose I want to pull back all departments for a given Division in a given Location. If I set up another 'Junction Table' for Division and Department then I can't see how I would differentiate Division by Location? Division_Department DivisionID(FK) DepartmentID(FK) Location_Division Division_Department LocationID DivisionID DivisionID DepartmentID 1 1 1 1 1 2 1 2 2 1 2 1 2 2 2 2 Do I need to expand the number of columns in my 'Junction Table' e.g. Location_Division_Department LocationID(FK) DivisionID(FK) DepartmentID(FK) Location_Division_Department LocationID DivisionID DepartmentID 1 1 1 1 1 2 1 1 3 2 1 1 2 1 2 2 1 3

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  • Help me with DB design

    - by eugeneK
    Hi, i'm developing text ads system. Some small clone of Google Ads. Here is diagram with common tables. Basically make it short, advertiser can have up to 10 variant of same campaign with different text variations, can geo-target his ads and unique impressions count only for IP that haven't been on certain site for more than 24 hours. Pretty simple but the question is what i lack in here from your experience because later it would much harder to fix design flaws and some of you probably done something alike also many SQL gurus in here so maybe i did over normalized DB or did not normalized as needed ? Second question is. My end goal is to get ads for user from ie. Germany that haven't seen same ad on same site for 24 hours as long as ads fit country of user. Each impression is count same as each click if there is one. I need to get 5 "random" ads based on IP, Country and higher CPC (pay per click). How can i achieve this with current design or maybe to design database the way it would be easy to get ads and show stats for advirtisers... thanks for any help...

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  • MYSQL - SImple database design

    - by sequelDesigner
    Hello guys, I would like to develop a system, where user will get the data dynamically(what I mean dynamic is, without reloading pages, using AJAX.. but well, it does not matter much). My situation is like this. I have this table, I called it "player", in this player table, I will store the player information like, player name, level, experience etc. Each player can have different clothes, start from tops(shirts), bottoms, shoes, and hairstyle, and each player can have more than 1 tops, bottoms, shoes etc. What I am hesitated or not very sure about is, how do you normally store the data? My current design is like this: Player Table =========================================================================================== id | name | (others player's info) | wearing | tops | bottoms =========================================================================================== 1 | player1 | | top=1;bottom=2;shoes=5;hair=8 | 1,2,3| 7,2,3 Tops Table ===================== id | name | etc... ===================== 1 | t-shirt | ... I am not sure if this design is good. If you are the database designer, how would you design the database? Or how you will store them? Please advise. Thanks

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  • Eclipc java,writting a program [closed]

    - by ghassar
    I have an important exercise for that i found in the internet please i need help in using eclipc java thanks i have to design, implement, test and document a Java program (a set of classes) for one of the following problem specifications: Problem 1 – Jubilee Estate Agency Property Management System A local Estate Agent would like a prototype system to keep track of properties that are offered for sale. The Estate Agent sells domestic and commercial properties. You will need to define classes that represent the Estate Agency System. You should design your system and the classes that you will need before starting coding. Your system must have a graphical user interface and be designed and developed using the object-oriented principles of the MVC architecture design pattern i.e. the user interface class must be separate from the other classes. The initial basic requirements for the system are as follows: • Include a list of domestic properties for sale that include details of: address, description, selling price, and number of rooms • Include a list of commercial properties for sale that include details of: address, description, selling price, and area in square metres • Enable the properties that are for sale to be viewed on the screen • Allow the customer to select one or more properties to be placed on a ‘viewing list’ so that the properties can be visited in person • Display on the screen the viewing list that shows the details of the properties chosen • Provide a basic search facility to find properties that are for sale in a particular price band and display the results • Enable a property to be marked as sold

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  • What good books are out there on program execution models? [on hold]

    - by murungu
    Can anyone out there name a few books that address the topic of program execution models?? I want a book that can answer questions such as... What is the difference between interpreted and compiled languages and what are the performance consequences at runtime?? What is the difference between lazy evaluation, eager evaluation and short circuit evaluation?? Why would one choose to use one evaluation strategy over another?? How do you simulate lazy evaluation in a language that favours eager evaluation??

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  • Requring static class setter to be called before constructor, bad design?

    - by roverred
    I have a class, say Foo, and every instance of Foo will need and contain the same List object, myList. Since every class instance will share the same List Object, I thought it would be good to make myList static and use a static function to set myList before the constructor is called. I was wondering if this was bad, because this requires the setter to be called before the constructor? If the person doesn't, the program will crash. Alternative way would be passing myList every time.

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  • Well written open source java projects

    - by Algorist
    I want to improve my design and programming skills by understanding design & code of open source projects. I downloaded hadoop,groovy but they are very difficult to follow. I am not having a clue of how to follow this code without having a high level overview of the design. Any suggestions?? Thank you.

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  • Developing multiple user interfaces for an application

    - by denizkocak
    I want to develop an application which has a graphical user interface that could be developed by using different widget toolkits. For example I want to use Qt, GTK+ or even ncurses as a building block for my user interface for the same application. Moreover users could choose which GUI implementation will be used during the next startup of the application without recompiling it first. I wonder what are possible design strategies and design patterns used in the implementation of this design?

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  • Object oriented n-tier design. Am I abstracting too much? Or not enough?

    - by max
    Hi guys, I'm building my first enterprise grade solution (at least I'm attempting to make it enterprise grade). I'm trying to follow best practice design patterns but am starting to worry that I might be going too far with abstraction. I'm trying to build my asp.net webforms (in C#) app as an n-tier application. I've created a Data Access Layer using an XSD strongly-typed dataset that interfaces with a SQL server backend. I access the DAL through some Business Layer Objects that I've created on a 1:1 basis to the datatables in the dataset (eg, a UsersBLL class for the Users datatable in the dataset). I'm doing checks inside the BLL to make sure that data passed to DAL is following the business rules of the application. That's all well and good. Where I'm getting stuck though is the point at which I connect the BLL to the presentation layer. For example, my UsersBLL class deals mostly with whole datatables, as it's interfacing with the DAL. Should I now create a separate "User" (Singular) class that maps out the properties of a single user, rather than multiple users? This way I don't have to do any searching through datatables in the presentation layer, as I could use the properties created in the User class. Or would it be better to somehow try to handle this inside the UsersBLL? Sorry if this sounds a little complicated... Below is the code from the UsersBLL: using System; using System.Data; using PedChallenge.DAL.PedDataSetTableAdapters; [System.ComponentModel.DataObject] public class UsersBLL { private UsersTableAdapter _UsersAdapter = null; protected UsersTableAdapter Adapter { get { if (_UsersAdapter == null) _UsersAdapter = new UsersTableAdapter(); return _UsersAdapter; } } [System.ComponentModel.DataObjectMethodAttribute (System.ComponentModel.DataObjectMethodType.Select, true)] public PedChallenge.DAL.PedDataSet.UsersDataTable GetUsers() { return Adapter.GetUsers(); } [System.ComponentModel.DataObjectMethodAttribute (System.ComponentModel.DataObjectMethodType.Select, false)] public PedChallenge.DAL.PedDataSet.UsersDataTable GetUserByUserID(int userID) { return Adapter.GetUserByUserID(userID); } [System.ComponentModel.DataObjectMethodAttribute (System.ComponentModel.DataObjectMethodType.Select, false)] public PedChallenge.DAL.PedDataSet.UsersDataTable GetUsersByTeamID(int teamID) { return Adapter.GetUsersByTeamID(teamID); } [System.ComponentModel.DataObjectMethodAttribute (System.ComponentModel.DataObjectMethodType.Select, false)] public PedChallenge.DAL.PedDataSet.UsersDataTable GetUsersByEmail(string Email) { return Adapter.GetUserByEmail(Email); } [System.ComponentModel.DataObjectMethodAttribute (System.ComponentModel.DataObjectMethodType.Insert, true)] public bool AddUser(int? teamID, string FirstName, string LastName, string Email, string Role, int LocationID) { // Create a new UsersRow instance PedChallenge.DAL.PedDataSet.UsersDataTable Users = new PedChallenge.DAL.PedDataSet.UsersDataTable(); PedChallenge.DAL.PedDataSet.UsersRow user = Users.NewUsersRow(); if (UserExists(Users, Email) == true) return false; if (teamID == null) user.SetTeamIDNull(); else user.TeamID = teamID.Value; user.FirstName = FirstName; user.LastName = LastName; user.Email = Email; user.Role = Role; user.LocationID = LocationID; // Add the new user Users.AddUsersRow(user); int rowsAffected = Adapter.Update(Users); // Return true if precisely one row was inserted, // otherwise false return rowsAffected == 1; } [System.ComponentModel.DataObjectMethodAttribute (System.ComponentModel.DataObjectMethodType.Update, true)] public bool UpdateUser(int userID, int? teamID, string FirstName, string LastName, string Email, string Role, int LocationID) { PedChallenge.DAL.PedDataSet.UsersDataTable Users = Adapter.GetUserByUserID(userID); if (Users.Count == 0) // no matching record found, return false return false; PedChallenge.DAL.PedDataSet.UsersRow user = Users[0]; if (teamID == null) user.SetTeamIDNull(); else user.TeamID = teamID.Value; user.FirstName = FirstName; user.LastName = LastName; user.Email = Email; user.Role = Role; user.LocationID = LocationID; // Update the product record int rowsAffected = Adapter.Update(user); // Return true if precisely one row was updated, // otherwise false return rowsAffected == 1; } [System.ComponentModel.DataObjectMethodAttribute (System.ComponentModel.DataObjectMethodType.Delete, true)] public bool DeleteUser(int userID) { int rowsAffected = Adapter.Delete(userID); // Return true if precisely one row was deleted, // otherwise false return rowsAffected == 1; } private bool UserExists(PedChallenge.DAL.PedDataSet.UsersDataTable users, string email) { // Check if user email already exists foreach (PedChallenge.DAL.PedDataSet.UsersRow userRow in users) { if (userRow.Email == email) return true; } return false; } } Some guidance in the right direction would be greatly appreciated!! Thanks all! Max

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  • Entity Framework and multi-tenancy database design

    - by Junto
    I am looking at multi-tenancy database schema design for an SaaS concept. It will be ASP.NET MVC - EF, but that isn't so important. Below you can see an example database schema (the Tenant being the Company). The CompanyId is replicated throughout the schema and the primary key has been placed on both the natural key, plus the tenant Id. Plugging this schema into the Entity Framework gives the following errors when I add the tables into the Entity Model file (Model1.edmx): The relationship 'FK_Order_Customer' uses the set of foreign keys '{CustomerId, CompanyId}' that are partially contained in the set of primary keys '{OrderId, CompanyId}' of the table 'Order'. The set of foreign keys must be fully contained in the set of primary keys, or fully not contained in the set of primary keys to be mapped to a model. The relationship 'FK_OrderLine_Customer' uses the set of foreign keys '{CustomerId, CompanyId}' that are partially contained in the set of primary keys '{OrderLineId, CompanyId}' of the table 'OrderLine'. The set of foreign keys must be fully contained in the set of primary keys, or fully not contained in the set of primary keys to be mapped to a model. The relationship 'FK_OrderLine_Order' uses the set of foreign keys '{OrderId, CompanyId}' that are partially contained in the set of primary keys '{OrderLineId, CompanyId}' of the table 'OrderLine'. The set of foreign keys must be fully contained in the set of primary keys, or fully not contained in the set of primary keys to be mapped to a model. The relationship 'FK_Order_Customer' uses the set of foreign keys '{CustomerId, CompanyId}' that are partially contained in the set of primary keys '{OrderId, CompanyId}' of the table 'Order'. The set of foreign keys must be fully contained in the set of primary keys, or fully not contained in the set of primary keys to be mapped to a model. The relationship 'FK_OrderLine_Customer' uses the set of foreign keys '{CustomerId, CompanyId}' that are partially contained in the set of primary keys '{OrderLineId, CompanyId}' of the table 'OrderLine'. The set of foreign keys must be fully contained in the set of primary keys, or fully not contained in the set of primary keys to be mapped to a model. The relationship 'FK_OrderLine_Order' uses the set of foreign keys '{OrderId, CompanyId}' that are partially contained in the set of primary keys '{OrderLineId, CompanyId}' of the table 'OrderLine'. The set of foreign keys must be fully contained in the set of primary keys, or fully not contained in the set of primary keys to be mapped to a model. The relationship 'FK_OrderLine_Product' uses the set of foreign keys '{ProductId, CompanyId}' that are partially contained in the set of primary keys '{OrderLineId, CompanyId}' of the table 'OrderLine'. The set of foreign keys must be fully contained in the set of primary keys, or fully not contained in the set of primary keys to be mapped to a model. The question is in two parts: Is my database design incorrect? Should I refrain from these compound primary keys? I'm questioning my sanity regarding the fundamental schema design (frazzled brain syndrome). Please feel free to suggest the 'idealized' schema. Alternatively, if the database design is correct, then is EF unable to match the keys because it perceives these foreign keys as a potential mis-configured 1:1 relationships (incorrectly)? In which case, is this an EF bug and how can I work around it?

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  • How should I design my database API commands? [closed]

    - by WebDev
    I am developing a database API for a project, with commands for getting data from the database. For example, I have one gib table, so the command for that is: getgib name alias limit fields If the user pass their name: getgib rahul Then it will return all gib data whose name is like rahul. If an alias is given then it will return all the gib owned by the user whose alias (userid) was given. I want to design the commands: limit: to limit the record in query, fields: extra fields I want to add in the select query. So now the commands are set, but: I want the gibs by the gibid, so how to make this or any suggestion to improve my command is welcome. If the user doesn't want to specify the name, and he wants only the gibs by providing alias, then what separator should I use instead of name?

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  • How do game programmers design their classes to reuse in AI, network and play and pass mode?

    - by Amogh Talpallikar
    For a two player game where, your opponent could be on the network, CPU itself or near you where you would play turn by turn on the same machine. How do people design classes for re-use ? I am in a similar situation and have no experience in making such complex games. But here is what I have thought, If I am a player object , I should only be interacting with the GameManager or GameEngine Singleton , from which I will get various notifications about the game status. I dont care where and who my opponent is, this GameManager depending upon the game mode, will interact with gameNetworkManager , or AI tell me what the opponent played. I am not sure about the scenario where we play and pass [turn by turn on same machine]. Hoping for a brief but clear explanation or at least a link to a similar resource.:)

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  • How to Design a Relational Database; PASS Precon Swag and it’s “Symbolism”

    - by drsql
    Update! 10 more books added to the cadre from my friends at Red-Gate. With less than a week to go, I am starting to pack up for Charlotte and PASS 2013. I love that it is in Charlotte this year so I can drive and bring along some goodies to give away. Books and toys mostly, a variety of which were chosen rather specifically for some manner of symbolism with a tie in to database design for the most part. (Okay, symbolism is perhaps a bit of a stretch, but I have tied everything, even the goofy stuff,...(read more)

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  • Name of web design technique with vertically contiguous but separate screen-sized blocks?

    - by Chad Schultz
    I don't know the proper name for this, which makes it hard to Google it or describe this. On a site like http://p2theme.com/ as you scroll down you see that content is arranged into screen-sized chunks, each with its own chunk of content, each with a different background color, making them visually distinctive. I've seen this used more and more frequently on websites, but don't know what it's called. People have tried telling me "responsive design" or "flat UI" or "infinite scroll" or "parallax" -- but those are completely different things. What do you call this technique?

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  • Design for future changes or solve the problem at hand.

    - by Naveen
    While writing the code or during design do you try to generalize the problem at the first instance itself or try to solve that very specific problem. I am asking this because, trying to generalize the problem tends to complicate the things (which may not be necessary) and on the otherhand it will be very difficult to extend the specific solution if there is a change in the requirement. I guess the solution is to find the middle path which is easier said than done. How do you tackle this type of problem ? If you start generalizing it at what point of time you know that this much of generalization is sufficient ?

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  • How to decide whether to implement an operation as Entity operation vs Service operation in Domain Driven Design?

    - by Louis Rhys
    I am reading Evans's Domain Driven Design. The book says that there are entity and there are services. If I were to implement an operation, how to decide whether I should add it as a method on an entity or do it in a service class? e.g. myEntity.DoStuff() or myService.DoStuffOn(myEntity)? Does it depend on whether other entities are involved? If it involves other entities, implement as service operation? But entities can have associations and can traverse it from there too right? Does it depend on stateless or not? But service can also access entities' variable, right? Like in do stuff myService.DoStuffOn, it can have code like if(myEntity.IsX) doSomething(); Which means that it will depend on the state? Or does it depend on complexity? How do you define complex operations?

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  • Program instantly closing [migrated]

    - by Ben Clayton
    I made this program and when I compiled it there were no errors but the program just instantly closed, any answers would be appreciated. #include <iostream> //Main commands #include <string> // String commands #include <windows.h> // Sleep using namespace std; int main () { //Declaring variables float a; bool end; std::string input; end = false; // Making sure program doesn't end instantly cout << "Enter start then the number you want to count down from." << ".\n"; while (end = false){ cin >> input; cout << ".\n"; if (input.find("end") != std::string::npos) // Ends the program if user types end end = true; else if (input.find("start" || /* || is or operator*/ "restart") != std::string::npos) // Sets up the countdown timer if the user types start { cin >> a; cout << ".\n"; while (a>0){ Sleep(100); a = a - 0.1; cout << a << ".\n"; } cout << "Finished! Enter restart and then another number, or enter end to close the program" << ".\n"; } else // Tells user to start program cout << "Enter start"; } return 0; // Ends program when (end = true) }

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  • Is there a good design pattern for this messaging class?

    - by salonMonsters
    Is there a good design pattern for this? I want to create a messaging class. The class will be passed: the type of message (eg. signup, signup confirmation, password reminder etc) the client's id The class needs to then look up the client's messaging preferences in the db (whether they want communication by email, sms or both) Then depending on the client's preference it will format the message for the medium (short version for sms, long form for email) and send it through our mail or sms provider's API. Because the fact that we want to be able to change out email and sms providers if need be I wondered if the Command Pattern would be a good choice.

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  • Prepared statement alternatives for this middle-man program?

    - by user2813274
    I have an program that is using a prepared statement to connect and write to a database working nicely, and now need to create a middle-man program to insert between this program and the database. This middle-man program will actually write to multiple databases and handle any errors and connection issues. I would like advice as to how to replicate the prepared statements such as to create minimal impact to the existing program, however I am not sure where to start. I have thought about creating a "SQL statement class" that mimics the prepared statement, only that seems silly. The existing program is in Java, although it's going to be networked anyways so I would be open to writing it in just about anything that would make sense. The databases are currently MySQL, although I would like to be open to changing the database type in the future. My main question is what should the interface for this program look like, and does doing this even make sense? A distributed DB would be the ideal solution, but they seem overly complex and expensive for my needs. I am hoping to replicate the main functionality of a distributed DB via this middle-man. I am not too familiar with sql-based servers distributing data (or database in general...) - perhaps I am fighting an uphill battle by trying to solve it via programming, but I would like to make an attempt at least.

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  • Is it possible to design a multiplayer game which can be played from different devices?

    - by user9820
    I want to design a online multiplayer game for all gaming devices e.g. Desktop PC, internet browser, android phones, android tablets, iphone, ipad, XBOX 360 etc. Now my main requirement is that, I want all devices can be used to play the game in multiplayer mode toghether i.e. One player can be connected using PC another using android phone and other may be with iphone or ipad. My doubts are - How to make all devices to connect to common game server? What will be the logic for graphics and texture because all devices screen will be of different aspect ratio?

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  • How would you design an application with many target platforms and devices?

    - by Pierre 303
    I'm in a very beginning of the design phase of an application that will have to run in the following platforms/devices: Desktop: Windows, Linux & Mac Mobile: Android, iPhone/iPad & Windows Phone 7 Web: Silverlight I will use C# on Mono and I want to maximize code re-usability. Except for the desktop (I'll use WinForms/GTK#), my concern is related to many different GUI that I will face. What would be your approach? Obviously, the views will be different, but what about the controllers, data access, utility classes, etc. Is it really acceptable to share everything but the views?

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  • Are the technologies used in an application part of the architecture, or do they represent implementation/detailed design details?

    - by m3th0dman
    When designing and writing documentation for a project an architecture needs to be clearly defined: what are the high-level modules of the system, what are their responsibilities, how do they communicate with each other, what protocols are used etc. But in this list, should the concrete technologies be specified or this is actually an implementation detail and need to be specified at a lower level? For example, consider a distributed application that has two modules which communicate asynchronously via AMQP protocol, mediated by a message broker. The fact that these modules use the Spring AMQP library for sending and receiving messages is a fact that needs to be specified in the architecture or is a lower-level detailed design/implementation detail?

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  • Is Domain Driven Design useful / productive for not so complex domains?

    - by Elijah
    When assessing a potential project at work, I suggested that it might be advantageous to use a domain driven design approach to its object model. The project does not have an excessively complex domain, so my coworker threw this at me: It has been said, that DDD is favorable in instances where there is a complex domain model (“...It applies whenever we are operating in a complex, intricate domain” Eric Evans). What I'm lost on is - how you define the complexity of a domain? Can it be defined by the number of aggregate roots in the domain model? Is the complexity of a domain in the interaction of objects? The domain that we are assessing is related online publishing and content management.

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