This document describes the development of a REST web service for car renting using Spring. The service defines three core functions: retrieving a list of available cars, renting a car, and returning a rented car. It provides these functions through a REST interface and uses JSON to serialize data between the Java backend and clients. The document outlines setting up the Spring backend to implement this interface and convert between Java objects and JSON, and includes details on developing a Java client to test the service and potential next steps to build a web client.