# What is 'Representational State Transfer'? **URL:** \ **Category:** Rails\ **Created:** [April 27, 2009, 9:55pm UTC](https://www.ruby-forum.com/t/what-is-representational-state-transfer/166612 "2009-04-27T21:55:23Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![amita0204](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/e56c9b/32.png) [@amita0204](https://www.ruby-forum.com/u/amita0204)\ **Post date:** [April 27, 2009, 9:55pm UTC](https://www.ruby-forum.com/t/what-is-representational-state-transfer/166612/1 "2009-04-27T21:55:23Z")
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? Thanks, Amita. ---
**Author:** ![amita0204](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/e56c9b/32.png) [@amita0204](https://www.ruby-forum.com/u/amita0204)\ **Post date:** [April 27, 2009, 11:17pm UTC](https://www.ruby-forum.com/t/what-is-representational-state-transfer/166612/2 "2009-04-27T23:17:20Z")
I for one found this post very useful. On Mon, Apr 27, 2009 at 10:16 PM, Robert W. \< ---
**Author:** ![amita0204](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/e56c9b/32.png) [@amita0204](https://www.ruby-forum.com/u/amita0204)\ **Post date:** [April 27, 2009, 10:16pm UTC](https://www.ruby-forum.com/t/what-is-representational-state-transfer/166612/3 "2009-04-27T22:16:26Z")
Amita B. 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: Representational: 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](http://example.com/posts/1) represents the first Post resource in the posts collection. State: 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.” Hope that helps. ---
**Author:** ![amita0204](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/e56c9b/32.png) [@amita0204](https://www.ruby-forum.com/u/amita0204)\ **Post date:** [April 28, 2009, 12:33am UTC](https://www.ruby-forum.com/t/what-is-representational-state-transfer/166612/4 "2009-04-28T00:33:30Z")
Hi – Robert W. wrote: > Representational: > 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](http://example.com/posts/1) represents the first Post resource in the > posts collection. 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.” > State: > 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: [http://dablog.rubypal.com/2008/3/23/splitting-hairs-over-resource](http://dablog.rubypal.com/2008/3/23/splitting-hairs-over-resource) [http://dablog.rubypal.com/2008/4/24/splitting-hairs-over-resource-part-2](http://dablog.rubypal.com/2008/4/24/splitting-hairs-over-resource-part-2) specifically in a Rails context. (Wow, was that more than a year ago?) David – David A. Black / Ruby Power and Light, LLC Ruby/Rails consulting & training: [http://www.rubypal.com](http://www.rubypal.com) Now out in PDF: The Well-Grounded Rubyist ([The Well-Grounded Rubyist](http://manning.com/black2)) “Ruby 1.9: What You Need To Know” Envycasts with David A. Black [http://www.envycasts.com](http://www.envycasts.com) ---
**Author:** ![amita0204](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/e56c9b/32.png) [@amita0204](https://www.ruby-forum.com/u/amita0204)\ **Post date:** [April 28, 2009, 6:44am UTC](https://www.ruby-forum.com/t/what-is-representational-state-transfer/166612/5 "2009-04-28T06:44:06Z")
David A. Black wrote: > Hi – > > Robert W. wrote: > > > Representational: > > 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](http://example.com/posts/1) represents the first Post resource in the > > posts collection. > > 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.” Absolutely. Thanks David for this elaboration. > 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. Nice explanation. I look forward to reading your articles when I have a few spare moments. ---
**Author:** ![amita0204](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/e56c9b/32.png) [@amita0204](https://www.ruby-forum.com/u/amita0204)\ **Post date:** [April 28, 2009, 10:04pm UTC](https://www.ruby-forum.com/t/what-is-representational-state-transfer/166612/6 "2009-04-28T22:04:42Z")
JDM wrote: > “Representational State Transfer defines a convention for using HTTP > to both identify and manipulate related information that is > conceptually mapped into an aggrregate construct referred to as a > Resource.” > Jim M. Quite succinct. I like it. ---
**Author:** ![amita0204](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/e56c9b/32.png) [@amita0204](https://www.ruby-forum.com/u/amita0204)\ **Post date:** [April 28, 2009, 6:47pm UTC](https://www.ruby-forum.com/t/what-is-representational-state-transfer/166612/7 "2009-04-28T18:47:21Z")
David, Your posts are certainly an interesting aside on the IMproper usage of the term “resource”, but it doesn’t (for me) answer the original question: “What is Representational State Transfer?” Like Amita, I struggle with this. My hope is to someday have a succinct way of expressing the answer, without being forced to convey all of the detailed nuamce of Fielding’s dissertation (which I don’t really grasp in any great detail). I kinda like where Robet was going, but I’ll suggest a slight rephrasing: “Representational State Transfer defines a convention for using HTTP to both identify and manipulate related information that is conceptually mapped into an aggrregate construct referred to as a Resource.” I repeat - I don’t really understand all of the detailed nuance. I’m struggling to create a simple articulation of the basic idea. Is my articulation sorta, kinda, in a way, maybe correct? How can my articulation be improved? Jim M. ---
**Author:** ![amita0204](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/e56c9b/32.png) [@amita0204](https://www.ruby-forum.com/u/amita0204)\ **Post date:** [April 29, 2009, 1:31am UTC](https://www.ruby-forum.com/t/what-is-representational-state-transfer/166612/8 "2009-04-29T01:31:38Z")
I guess I was trying to duck the issue, but I see that does nothiing to elucidate the use of the word “Representational” in the REST name. I’ll suggest this change (though its getting quite wordy): “Representational State Transfer defines a convention for using HTTP to both identify and manipulate related information that is conceptually mapped into an aggrregate construct referred to as a Resource, via the transfer between application components of Representations that contain the current or intended state of that Resource.” Whadda ya think? Jim M. On Apr 28, 4:35 pm, Robert W. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) ---
**Author:** ![amita0204](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/e56c9b/32.png) [@amita0204](https://www.ruby-forum.com/u/amita0204)\ **Post date:** [April 28, 2009, 11:35pm UTC](https://www.ruby-forum.com/t/what-is-representational-state-transfer/166612/9 "2009-04-28T23:35:15Z")
JDM wrote: > I kinda like where Robet was going, but I’ll suggest a slight > rephrasing: > > “Representational State Transfer defines a convention for using HTTP > to both identify and manipulate related information that is > conceptually mapped into an aggrregate construct referred to as a > Resource.” Thanks for the vote of confidence. I certainly don’t claim to be an expert on the subject. There are a lot of people smarter on this stuff than I, which is why I tried to remain somewhat abstract. I do like your rewording of my original thought. It certainly seems like a good start. However, as David pointed out in his excellent blog postings, this definition may still be omitting one important aspect of REST, which is the distinction between a “resource” and a “representation” of a resource. I feel that I have a good mental grasp on this distinction, even if I’m not so great at applying the concepts to the written word.