Minimize coupling with REST processes

While integrating systems, implementing access or processes is typically achieved through man ordered list of steps, where one expects specific results from the server.

Expecting specific results means coupling your client to a servers behavior, something that we want to minimize.

In REST clients, and in business process modeled following REST practices, we can reach lesser decoupling factors. Imagine the following system (among others) that buys products at amazon.com:


When there is a required item
And there is a basket
But didnt desire anything
Then desire this item as first item

When there is a required item
And there is a basket
Then desire this item

When it is a basket
And there are still products to buy
Then start again

When there is a payment
Then release payment information


The above code works and can be seen running in the last video from this post. In this Rest modelled process, several types of evolutions can happen on the server, without breaking the client:

1. After adding a product to the basket, if the server renders recommendations instead of your basket, the client still achieve its goal.

2. If some products are not found, the client is still able to pay for it.

3. If the server does not have the products, but links to another system in a affiliated program, we as clients will never notice it, and buy the products.

4. If we want to achieve the same goal in other systems that understand the same media type that we do, simply change the entry point..

Note the benefits from backward compatibility, forward compatibility and we are still capable to achieve our goals without knowing the existence of some changes on the protocol. We can even compare prices without changing one line of code, everything using well known media types as Atom. RDFa support can also be implemented.

This evolution power is not achieved in traditional process modelling, and several times, compatibility is left aside. This is something that REST and hypermedia brought us.

Mapping our process in a adaptable way using hypermedia was described in an article recently for the WWW2010 proceedings.

Now let’s imagine the traditional modelling:

1. Search
2. Add
3. Search
4. Add
5. Pay

In a typical web services + business processing scenario, how would a server notify me to access another system without changing one line of code in my client? It would break compatibility.

If the server now supports a limited quantity of items in your basket, your client will also break, while the adaptable REST client adapts itself and buys what it is capable of.

If our produt or company uses those traditional paths and every change on the service implies in heavy change costs for clients, thats a hint that your project is too much coupled, and a REST client as mentioned might help.

Tradicional web services decouple a little bit more than traditional RPC, but still provide this amount of coupling that cost our companies more than they were expecting to pay.

The following presentation 6 minutes presentation shows how to avoid some of this coupling from your server.

The entire video cast on the 3rd part from Rest from scratch is here:

This code achieves its results using Restfulie 0.8.0, with many thanks to everyone who contributed maturing this release: Caue Guerra, Luis Cipriani, Éverton Ribeiro, George Guimarães, Paulo Ahagon, Fabio Akita, Fernando Meyer and others.

Thanks to all feedback from Mike Amundsen, Jim Webber and Ian Robinson.

Is your client api code already adapting itself to changes?

(update: changed some of the “Then” clauses from the dsl for easier spotting of document messages instead of commands)

The Web and Rest (Rest from Scratch – Theory 1)

Rest is not only about http and the web, but an architectural style derived from the web and others.

In this 20 minutes video, we will see how the web has been capable of scaling, providing different services and being a more effective system than other human distributed systems alike (i.e. water distribution and electricity).

We move on to describing the basic characteristics of a rest architecture and how it leverages your system.

This is the first video on the Rest from Scratch – Theory. You can watch the other Rest From Scratch – Practice videos online here.

Watch the following video at vimeo or click here.

Rest from scratch – Part 2

This 20 minutes video shows how to move from a basic REST api to one which makes use of linked resources and adds semantic values to those links.

Did your REST api do that already? Great.

Otherwise, it’s time to move ahead and decouple a little bit further your clients from your server.

REST from scratch

This is the first post on a series of examples on how to use Rails and Restfulie on the server side and Restfulie and Mikyung on the client side to create REST based architectures.

On this 10 minutes video you will learn how it is possible to make several representations of one resource available on the server side (xml, json, atom and so on) and one line of code access and parse it on the client side.

This video shows how to access those basic REST api’s as Twitters, CouchDB which are based on http verbs and multiple URIs. The following videos shall demonstrate how to access more advanced REST API’s.

If you have any questions, join us at our mailing list.

Buying through REST: applying REST to the Enterprise

REST was a research result that left us with an open question, as its researcher suggested: it beautifully solves a lot of problems, but how to apply it on contemporary concerns that enterprise have?

REST Applied

After many talks, I have summed up a model, derived from REST constraints, that allows one to measure how his entire system (client and server) achieves a REST architecture.

The following video shows an example on how to start from a typical non restful architecture to adopting REST constraints and creating a buying process in any REST server.

So what is the power behing applied REST?

“Rest Applied” as I have exemplified, solves our contemporary concerns, filling the gap between Roy’s description and application’s usage, opening up a new world of possibilities.

The same way that REST ideas, although they were not called REST at that time, allowed web crawling to be an amazing client, “REST applied”, as described, can change the way our applications communicate with servers.

Why did we miss it? Because Roy’s description goes for with crawling examples, which benefit directly from content type negotiation. i.e. different languages, same resource and google post ranking it:

“In fact, the application details are hidden from the server by the generic connector interface, and thus a user agent could equally be an automated robot performing information retrieval for an indexing service, a personal agent looking for data that matches certain criteria, or a maintenance spider busy patrolling the information for broken references or modified content [39].”

But, “Not surprisingly, this exactly matches the user interface of a hypermedia browser. “… the client adapts itself to its current representation – limited to the client’s cleverness.

REST Applied takes those ideas to solve our problems, as some examples from Rest in Practice and procurement through rest.

Frameworks/libraries used

Restfulie gives better HTTP support to http libraries and provides a REST frameworks while Mikyung allows you to create your REST clients. With both of them you are ready to apply REST to enterprise problems.

Mikyung stands for “beauty capital” in Korean, in a attempt to reproduce what a beautiful rest client could look like when following REST constraints.