The scale of API integration is often unimaginable. It is often questioned how the pre-API world of software looked like. Take for instance a world without APIs; A narrative that weaves around the absence of instant messaging and chatbots. Facebook and Twitter would no longer work.
Imagine the end of News apps, weather forecast applications, and Google traffic updates.
API in full is “Application Programming Interface“. The sole role of API is to transfer data from one application to another. Think data-driven growth, hence APIs enable apps to request and send responses through various internet protocols. These protocols include HTTPS, SMTP, etc.
SOAP and REST are two of the most sought after web interface services out there. In other words, both are styles that approach the concept of data transmission from a very unique point of view.
Initially, we only had SOAP. Software architects would integrate the interface in their messaging platforms back in the day.
In fact, almost all web services that had a messaging platform within them had implemented SOAP. With time and sophistication of network frameworks, demand for lightweight mobile and web applications grew. Quickly, developers turned to REST because it provided a seamless way of message integration.
Today, almost all social media networks have implemented REST. They go on to provide these REST APIs to other developers, which in many cases are designed to serve different purposes. REST stands for Representational state transfer, while SOAP is Simple Object Access Protocol.
What is SOAP?
SOAP works on decentralized and distributed environments as a means of data interchange. The highlight for SOAP is its ability to work with different application protocol layers; especially; HTTP, TCP, UDP, and SMTP. Usually, SOAP transmits data back in an Extended Markup Language (XML) format.
As with REST, SOAP doesn’t assume a Point to point communication path. Error handling and security authorization are inbuilt within the protocol. The lack of a defined point to point communication path makes SOAP appropriate for distributed platforms. Therefore, a notable point of contrast between SOAP vs REST is in the communication variable.
Noteworthy, SOAP follows a definite set of steps for encoding XML format messages. These encoded messages are usually returned by the API. To have a better understanding of its working, it’s important to scrutinize the structure of an API XM file.
(A typical XML file)
Parts of a SOAP XML File
1. Envelope (Compulsory) – Beginning and ending tag of the message.
2. Header (Optional) – Features the message’s optional attributes. It gives developers the ability to extend their message in a decentralized and modular format.
3. Body (Compulsory) – Consists of XML data that the server has transmitted to the receiver.
4. Fault (Optional) – The part of the message that carries or handles errors encountered during the transmission process.
What is REST?
Developers in need of designing a loosely coupled application on top of the HTTP protocol layer; are advised to use REST. The best thing about REST is its ability to be tweaked according to developers’ preferences.
Therefore, developers can implement REST guidelines according to their own style and needs. Software developers usually refer to applications developed with the REST architecture as Restful Web Services.
The following architectural constraints are important while creating a REST API.
1. Uniform constraints – Requests from different user clients should look similar.
2. Client-Server Separation – The server and client should be separate entities. Both should interact with each other only through requests and responses.
3. Statelessness – Server side sessions are prohibited.
4. Cacheable resource – Clients should be notified whether received resources are cacheable or not. This prevents them from requesting similar resources twice.
5. Layered systems – Any number of layers between the client and the server should not affect data transmission.
6. Code on Demand (Optional) – If required, responses may contain executable code. This code can easily be executed by the client separately from the server.
Most APIs today are built on REST, SOAP or JSON. The choice of protocol is solely reliant on the needs of the organization. Factors such as target client, flexibility and scalability also come into play. Amidst the three choices, you only have to compare the needs of your company against the background of what is on offer.