本文是RESTful Web Services: A Tutorial的笔记：
REST stands for Representational State Transfer, which is an architectural style for networked hypermedia applications, it is primarily used to build Web services that are lightweight, maintainable, and scalable. A service based on REST is called a RESTful service. REST is not dependent on any protocol, but almost every RESTful service uses HTTP as its underlying protocol.
尽管REST本身不依赖任何协议，但是事实上RESTful服务基本都使用HTTP协议。
RESTful服务本身的特性：
Every system uses resources. These resources can be pictures, video files, Web pages, business information, or anything that can be represented in a computer-based system. The purpose of a service is to provide a window to its clients so that they can access these resources. Service architects and developers want this service to be easy to implement, maintainable, extensible, and scalable. A RESTful design promises that and more. In general, RESTful services should have following properties and features, which I’ll describe in detail:
Representations
Messages
URIs
Uniform interface
Stateless
Links between resources
Caching
具体来说：
Representations：使用JSON或XML；
Messages，URIs和Uniform interface：使用HTTP协议；
Stateless：很重要，不同的request之间不能有依赖。