What are the ways to integrate with external systems?

Question

Programming

At the exam, they asked the question: "methods of integration with external systems
" wsdl file.
He didn’t answer anything else, for which he received a triple, it’s very embarrassing and I would like to hear what other ways to integrate with external systems are and how the specifications for such interaction are described?

Answer 1

Of all the external systems, Google is the most important for us .