Why?

  In order to manage and maintain the increasingly complex data requirements of modern web/mobile apps.

Even if RESTful (with HATEOAS specification) API normalize and bring solutions for generic API, when performance and custom query become necessary GraphQL is the best solution.

Perhaps a shower before? SOAP = Service Oriented Application Protocol

Client & Server share a WSDL = Web Service Description Language (in XML the less verbose language :D)

• Use HTTP POST method
• HTTP Status Code already 200
• Send XML language

Some problems: verbose, use HTTP POST only (no respect Idempotent principle), heavy

REST = REpresentational State Transfert

• It must be a client-server system
• It has to be stateless
• It has to support a caching system
• It has to be uniformly accessible
• It has to be layered (support scalability)
• It may be able to transfer executable code

REST Implementation

• Use resources or Aggregation head in order to represent data
• Use HTTP Methods (CRUD = POST, GET, PUT, DELETE)
• Return appropriate HTTP status codes (Here)

HATEOAS = Hypermedia As The Engine Of Application State

Like with WEB technology use API with hyperlinks model, thus return data contains links allow to use with the current resource(s) requested

In order to normalize and structure some notations have been created like HAL = Hypertext Application Language
But also many libraries like traverson for frontend (with HAL)