The number of tiers (n-tier) architecture generally divides an application into three tiers—the presentation, logic, and data tiers. It physically separates the different parts of an application instead of doing so conceptually or logically, as in the so-called “model-view-controller (MVC) framework.” The n-tier layers are connected linearly, meaning all communication goes through the middle layer—the logic tier.
The n-tier architecture also refers to a program distributed among three or more separate computers in a distributed network. The most common form is the 3-tier application that comprises a user interface (UI) programming in the user’s computer, the business logic in a more centralized computer, and the required data in a computer that manages a database. This model allows software developers to create reusable applications with maximum flexibility.
You can liken n-tiers, therefore, to the walls in a house, with only one entry door (i.e., the front door and no back door) and rooms arranged in a single file, that separate one room from another. In this case, the house is the application, and the rooms (i.e., living room and kitchen, bedroom, and bathroom) are the tiers. Everyone that enters the house has to travel in only one direction to go in or out.
Read More about the Number of Tiers (N-Tier) Architecture
As mentioned, the most common kind of n-tier or multitier architecture is the 3-tier model.
What Are the Usual Parts of an N-Tier Architecture Model?
Let’s take a closer look at the components of a typical 3-tier model—the presentation, logic, and data tiers.
1. Presentation Tier
The presentation tier is the topmost layer in the n-tier architecture. It is also known as the UI—what users see when they access an application or system. Its primary task is to translate tasks and results into something users can understand.
2. Logic Tier
The logic tier coordinates applications, processes, and commands; makes logical decisions and evaluations; and performs calculations. It is where data gets processed to produce results. It also moves and processes data to and from the two other tiers—the presentation and data tiers.
3. Data Tier
The data tier stores and retrieves data from a database or file system. That information is then passed on to the logic tier for processing, and the results go to the presentation layer so users can see them.
Here’s a diagram showing how users can get the total sales for a year from an n-tier framework.
What Are the Benefits of Using the N-Tier Architecture?
Using the n-tier architecture provides these benefits.
- Scalability: Users can adjust the amount of resources for one tier without affecting the other tiers.
- Individual management: Users can prevent cascade effects, thus isolating maintenance.
- Security: Users can secure each tier differently from the others, depending on who can access it and its contents.
- More efficient development: Three different teams can work on each tier collaboratively and simultaneously. That way, work gets done faster and more accurately since issues can be fixed as they crop up. All adjustments made to the data tier, for instance, can be addressed in the logic and presentation tiers simultaneously. Testing if they work together can thus be done as soon as the modifications are done.
- Ease of adding new features: Users can introduce new features to a tier without affecting the others.
- Reusability: Because the application is divided into independent tiers, users can easily reuse each tier for other software projects. If they want to use the same logic, for example, on a different data set, they can just replicate the logic and presentation tiers and create a new data tier.
How Does a Simple N-Tier Architecture Work?
Let’s look at a web-based patient appointment application for a medical center.
A user interacts with the presentation tier, let’s say, a web browser. He logs in and selects the doctor he would like to make an appointment with. The logic tier accesses the presentation tier to verify the user’s identity. It also determines which scheduling and validation forms stored in a web server the user needs to fill in. After that, the logic tier connects to the data tier, where the patient, form, doctor, and schedule databases are located. The appointment gets logged into the database. The approved schedule is sent to the user. The user sees an appointment confirmation onscreen.
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N-tier architectures are suitable for situations where the communication links are very fast in terms of transmitting and receiving information. That is vital because the communication links enable communication between the different components.
Furthermore, this architecture is primarily suitable for applications where scalability, security, ease of maintenance, and reusability are a priority.
Key Takeaways
- The number of tiers (n-tier) architecture divides an application or system into tiers, usually three—the presentation, logic, and data tiers.
- The n-tier architecture physically separates the different parts of an application or system instead of doing so conceptually or logically.
- The n-tier layers are connected linearly, meaning all communication goes through the middle layer—the logic tier.
