We have over the past few years come across many APIs that have claimed that they use a RESTful approach. Though we were inclined to believe them at first upon close examination, it was revealed that they fell short of the requirements and constraints of RESTful design. RESTful design constraints were laid out by Dr. Fielding who was the first person to address RESTful APIs in his 2000 doctoral thesis. According to Dr. Fielding, web API design that uses RESTful design will have six constraints three of which are well known while the others are not. We discuss those constraints below.
Uniformity with the Interface
The easiest way to ensure that the server is decoupled from the client is to implement a uniform interface which will enable the independent evolution of the application and that too without needing actions, models, and services along with its API layer. Having a uniform interface allows for the client to easily communicate with the server using one language that is independent of the backend architecture. The interface will provide a reliable and standardized way of communication between clients and servers via the URI and by using HTTP’s resources.
A Multi-Layered System
Now a layered system is comprised of multiple layers which may sound complicated. Every layer will have its own specific function and will be responsible for its own set of rules. It is like a Model View Controller whereby each layer will have a responsibility of its own.
That will dictate how the model uses data while the controller focuses on all incoming actions and the view focusing on output. Each layer happens to be independent but has open communication with other layers. Now, this same principle also applies to RESTful API design with each segment of the API’s architecture being held together by the hierarchy making it scalable, and modular.
Layered systems also help API developers to encompass if needed legacy systems. So, they have the option of moving often less frequently used function into a different library and yet still shield the more common parts of the design. Some other benefits of a layered system have to be the ability to move systems out and in of the architecture as its technology evolves which in turn improves the longevity and overall flexibility as long as the modules are coupled loosely.
Layered systems are also more secure as it allows for stopping attacks directly at the proxy layer which prevents attackers from getting to the server’s architecture. It also keeps critical data relating to the architecture behind a strict firewall that blocks the client from interacting with that server which is ingenious.
The Required “Code on Demand”
It is arguably a constraint which is least known because it is optional. Having this code on demand feature allows for the code or its applets to be easily transmitted using the API from within the application. So, you can create smart applications which happen to be independent of a strict coded structure. Though because this constraint was seen as being ahead of its time a decade ago, it was not widely adopted amongst then API developers. Today the focus on developing AI enabled applications has brought back the need for this constraint stronger and harder than ever before.
The six constraints, three of which we discussed above makeup what is called the Representational State Transfer or REST. Each constraint builds upon the other to create a powerful, flexible and complex programming interface. It is what makes it possible to develop apps for the web as we know it today.