With the pattern specification, we can extract this logic and reuse it. In the same way, this pattern can be used to build queries because the "where" clause must receive a Boolean expression in the same way to filter data. Repository contracts This piece of the code will contain the interface of the repositories. These repositories will be responsible of the interaction with the data layer. Data persistence This layer is one of the most important pieces in a domain-oriented architecture, because your application is mainly created to manage an important volume of data. In this layer you can find the implementation of the repositories (Repository Pattern) using the interfaces (contracts) implemented in the domain layer. These repositories will directly use the persistence system. This persistence system will usually be an ORM (NHibernate, Entity Framework, etc). If you don't use some ORM, repositories will be responsible to map data between a data source (usually databases) and the domain model, in the same way that in MVP pattern the domain is mapped to a view-model.
Presentation Layer Everybody knows the responsibility of this layer but some people doesn't know how to implement it in a right way. In my experience, I have found implementations with a lot of code. You must think that the presentation layer is a part of the application that is very difficult to test automatically (unit testing). If you write a lot of code, you have a potentially dangerous layer because bugs cannot be found easily. For this reason, presentation patterns must be used, minimizing the quantity of code you implement that cannot be tested in unit tests. Consider using patterns like MVP for WinForms and applications, MVC in web applications and MVVM in Silverlight and WPF applications. These patterns allow you to delegate the responsibility to pieces of code that can be tested. In this layer, we will have the proxies to distributed services (WCF) or the interface of our business services. If you use IoC frameworks, it's very easy to allow that one non-distributed application can be transformed in a distributed architecture, because you only have to configure the IoC framework to use the services directly or to use distributed services proxies.
100% found this document useful (2 votes) 4K views 475 pages Description: N Layered DD Architecture Date uploaded Jun 08, 2011 Copyright © Attribution Non-Commercial (BY-NC) Available Formats PDF, TXT or read online from Scribd Did you find this document useful? 100% found this document useful (2 votes) 4K views 475 pages You're Reading a Free Preview Pages 13 to 15 are not shown in this preview. Pages 22 to 28 are not shown in this preview. Pages 32 to 36 are not shown in this preview. Pages 40 to 53 are not shown in this preview. Pages 66 to 82 are not shown in this preview. Pages 87 to 112 are not shown in this preview. Pages 135 to 145 are not shown in this preview. Pages 160 to 176 are not shown in this preview. Pages 186 to 193 are not shown in this preview. Pages 203 to 259 are not shown in this preview. Pages 288 to 289 are not shown in this preview. Pages 301 to 331 are not shown in this preview. Pages 343 to 394 are not shown in this preview. Pages 406 to 434 are not shown in this preview.
Andreas Hanemann Jeff W. Boote Eric L. Boyd Jérôme Durand Loukik Kudarimoti Roman Łapacz D. Martin Swany Szymon Trocha Jason Zurawski Part of the Lecture Notes in Computer Science book series (LNCS, volume 3826) Abstract In the area of network monitoring a lot of tools are already available to measure a variety of metrics. However, these tools are often limited to a single administrative domain so that no established methodology for the monitoring of network connections spanning over multiple domains currently exists. In addition, these tools only monitor the network from a technical point of view without providing meaningful network performance indicators for different user groups. These indicators should be derived from the measured basic metrics. In this paper a Service Oriented Architecture is presented which is able to perform multi-domain measurements without being limited to specific kinds of metrics. A Service Oriented Architecture has been chosen as it allows for increased flexibility and scalability in comparison to traditional software engineering techniques.
0 2. - Modules............................................................................................................................ 73 2. 6. - Model Subdivision and Work Context..................................................................... 76 2. 7. - Bounded Contexts.......................................................................................................... 8. - Relations between Contexts........................................................................................ 77 2. - Shared Kernel......................................................................................................... - Customer/Supplier................................................................................................. 78 2. - Conformist............................................................................................................... - Anti-Corruption Layer.......................................................................................... 79 2.
How It Works and Examples of N-Tier Architecture When it comes to n-tier architecture, a three-tier architecture is fairly common. In this setup, you have the presentation or GUI tier, the data layer, and the application logic tier. The application logic tier. The application logic tier is where all the "thinking" happens, and it knows what is allowed by your application and what is possible, and it makes other decisions. This logic tier is also the one that writes and reads data into the data tier. The data tier. The data tier is where all the data used in your application are stored. You can securely store data on this tier, do transaction, and even search through volumes and volumes of data in a matter of seconds. The presentation tier. The presentation tier is the user interface. This is what the software user sees and interacts with. This is where they enter the needed information. This tier also acts as a go-between for the data tier and the user, passing on the user's different actions to the logic tier.
The business must be delegated to the domain layer and its services. Of course, the domain layer is the most important part in a domain-oriented architecture. This is the core of the software. This layer must be absolutely loosely coupled. In this layer we can find: Domain entities The domain entities are the classes that represent the information that we want to manage with our application. This classes can or cannot have the same format that the data of the data repository. These classes must be POCO (plain old CLR object). Domain Service These services are oriented to manage the domain entities but these classes don't have code to persist the information. For example, we can develop the BankAccountService with a method MakeTransfer. These kinds of services represent the business logic of our application. Query Specifications The query specifications are linked to the Specification Pattern. This pattern allows us to export the typical flow control to some classes to be reused. We usually implement some code to control the input of a method and we have to rewrite this code in various methods.
In short, with n-tier architecture, you can adopt new technologies and add more components without having to rewrite the entire application or redesigning your whole software, thus making it easier to scale or maintain. Meanwhile, in terms of security, you can store sensitive or confidential information in the logic tier, keeping it away from the presentation tier, thus making it more secure. Other benefits include: More efficient development. N-tier architecture is very friendly for development, as different teams may work on each tier. This way, you can be sure the design and presentation professionals work on the presentation tier and the database experts work on the data tier. Easy to add new features. If you want to introduce a new feature, you can add it to the appropriate tier without affecting the other tiers. Easy to reuse. Because the application is divided into independent tiers, you can easily reuse each tier for other software projects. For instance, if you want to use the same program, but for a different data set, you can just replicate the logic and presentation tiers and then create a new data tier.
This is because when you work on one section, the changes you make will not affect the other functions. And if there is a problem, you can easily pinpoint where it originates. A More In-Depth Look at N-Tier Architecture N-tier architecture would involve dividing an application into three different tiers. These would be the logic tier, the presentation tier, and the data tier. Image via Wikimedia Commons The separate physical location of these tiers is what differentiates n-tier architecture from the model-view-controller framework that only separates presentation, logic, and data tiers in concept. N-tier architecture also differs from MVC framework in that the former has a middle layer or a logic tier, which facilitates all communications between the different tiers. When you use the MVC framework, the interaction that happens is triangular; instead of going through the logic tier, it is the control layer that accesses the model and view layers, while the model layer accesses the view layer.
Just imagine surfing on your favorite website. The presentation tier is the Web application that you see. It is shown on a Web browser you access from your computer, and it has the CSS, JavaScript, and HTML codes that allow you to make sense of the Web application. If you need to log in, the presentation tier will show you boxes for username, password, and the submit button. After filling out and then submitting the form, all that will be passed on to the logic tier. The logic tier will have the JSP, Java Servlets, Ruby, PHP and other programs. The logic tier would be run on a Web server. And in this example, the data tier would be some sort of database, such as a MySQL, NoSQL, or PostgreSQL database. All of these are run on a separate database server. Rich Internet applications and mobile apps also follow the same three-tier architecture. And there are n-tier architecture models that have more than three tiers. Examples are applications that have these tiers: Services – such as print, directory, or database services Business domain – the tier that would host Java, DCOM, CORBA, and other application server object.