What is the fundamental principle in designing RESTful services?

The fundamental principle in designing RESTful services is the use of the REST (Representational State Transfer) architectural style, which is based on the following key ideas:

• Use of standard HTTP methods (GET, POST, PUT, DELETE) for resource operations.
• Identification of resources through URIs.
• Statelessness: each request contains all the necessary information.
• Use of resource representations (e.g., JSON or XML).
• Caching to improve performance.

The main goal is to create simple, scalable, and easily maintainable web services that operate on resources through standard protocols and methods.