Robert Walker wrote:
Amita Bhatkhande wrote:
I have read about REST, but never really understood meaning of
'Representational State Transfer'. I tried to read Fielding's
dissertation, but did not understand this term and why has he used it.
What does it mean? Which state? What transfer?
I'm not sure anyone knows why Fielding used this term. I suppose he had
to call it something, so that's what he chose.
However, I'll try to explain it as I understand it:
The web consists of resources in the form of web pages that are
represented using a Uniform Resource Identifier (URI). REST extends this
definition to refer to other types of resources of an application (i.e.
database tables). Which, can also be represented using a URI.
http://example.com/posts/1 represents the first Post resource in the
A resource in the REST sense isn't anything as concrete as a database table, though. It's more conceptual. As Fielding says: "The resource is not the storage object. The resource is not a mechanism that the server uses to handle the storage object."
This is the current state of the resources.
Transfer (or more precisely State Transfer):
The act of modifying the current state of the resources. Adding a new
one, modifying an existing one, deleting an existing one, etc.
REST defines a convention of using HTTP to both represent and change the
state of resources. That's a close as I can come to defining
"Representational State Transfer."
My nutshell take on it is something like this:
A given system gives and receives representations of resources. A resource is a very high-level construct; a representation is more specific, and has a content-type and so forth. Resources don't. (Even more low-level are matters of storage, which may vary and which are not, themselves, either resources or representations.)
A resource is always in a given state. Resource states are altered via the exchange of representations. So if I want to correct the spelling of my name on a site, I submit a representation of my profile with the new spelling (probably in the form of a Web form). If I want to make sure it's OK, I request a representation (probably in the form of an HTML document) to inspect.
I've written a bit more about this on these blog posts:
specifically in a Rails context. (Wow, was that more than a year ago?)