在Richardson成熟度模型中定义了4个级别的API。这些被定义为:

level 0: any system that has a single endpoint for all its apis(SOAP or RPC fall in this category). Level 0 apis can also resemble "commands". level 1: a ResourceUri described system. This is a system that defines multiple entity-based URIs (instead of having a single endpoint like a level 0 systems would). These URIs can use different http actions (POST, GET, PUT, etc) to implement different actions against that resource. level 2: aka level 1 w/ a compliant use of Standard HTTP methods/verbs and multi status code responses level 3: aka level 2 plus HATEOAS (hypermedia included in the response which describes additional calls you can make)

虽然级别1、级别2和级别3可以被认为是REST系统，但只有更严格的级别(即级别2和级别3)才被认为是RESTful的。

所以本质上所有的RESTful api都是REST api，但并不是所有的REST api都是RESTful的

理查德森成熟度模型的定义

Web服务本质上是网站，其内容是由计算机程序而不是人消费的。REST是一套体系结构原则，它规定web服务应该最大限度地利用HTTP和其他web标准，以便程序获得人们已经可以从web中获得的所有好东西。REST经常与SOAP web服务和其他面向“远程过程调用”的web服务进行对比。

Stefan Tilkov在Parleys.com上关于REST的演讲非常棒，尤其是这个。

理查德森和Ruby的《Restful Web Services》是最好的一本书。

具象状态传输(REST)是软件体系结构的一种风格。正如Roy Fielding在一篇论文中描述的那样，REST是一种“架构风格”，基本上利用了现有的Web技术和协议。

RESTful通常用于指实现这种体系结构的web服务。

REST stands for representational state transfer. That means that state itself is not transferred but a mere representation of it is. The most common example is a pure HTML server based app (no javascript). The browser knows nothing about the application itself but through links and resources, the server is able transfer the state of the application to the browser. Where a button would normally change a state variable (e.g. page open) in a regular windows application, in the browser you have a link that represents such a state change.

这个想法就是使用超媒体。也许还能创造出新的超媒体类型。我们可以用javascript/AJAX扩展浏览器，并创建新的自定义超媒体类型。这样我们就有了一个真正的REST应用程序。

This is my short version of what REST stands for, the problem is that it is hard to implement. I personally say RESTful, when I want to make reference to the REST principles but I know I am not really implementing the whole concept of REST. We don't really say SOAPful, because you either use SOAP or not. I think most people don't do REST the way it was envisioned by it's creator Roy Fielding, we actually implement RESTful or RESTlike architectures. You can see his dissertation, and you will find the REST acronym but not the word RESTful.

“REST服务”和“REST式服务”是一回事。

基于REST的系统是任何遵循原始文档中定义的REST约定的系统，该文档创建了基于REST的网络应用程序的思想。

值得注意的是，RESTfulness有不同的等级。总的来说，REST是一种风格，而不是标准，因此有根据需要进行解释的空间。一个例子是分层资源url(例如/things/ID/relatedthings) vs平面url(例如/things/ID和/relatedthings?thing=ID)

谢谢你的回答。 阅读Alex Rodriguez的这篇文章，他认为RESTful web服务有4个基本特征:

显式地使用HTTP方法。 是无状态的。 公开类似目录结构的uri。 传输XML、JavaScript对象符号(JSON)或两者。