Contracts and Coupling in Resource Oriented Architecture

We've seen that most software developers in operation today are besotted by the vendor model. One of the symptoms of that malaise is the deeply ingrained idea of a contract. Basically, it would appear that, in the minds of typical software developers, there cannot possibly occur an interaction between software components without a predefined contract.

Of course, the contract they are talking about follows (albeit covertly) the implicit revenue model as ingrained in a typical software vendor's business plan. Software vendors make their living by locking into a contract with their customers.

But in cases where the utilization of the software product is not tied with any revenue model, the notion of a contract tends to lose its appeal. Like, for example, in cases where an open source community is bettering the services by utilizing the publicly vetted web standards and protocols.

There are no Unilateral Contracts

The web is a platform that publishes its capabilities in a unilateral fashion. Similar to any other publicly vetted service, the web is calibrated to serve the least common denominator.

For example, in all developed countries in the world there is a publicly vetted service called traffic. Various vehicles are free to enjoy the commodities that the public roads offer, mostly free of charge. However, the reason this service is made so freely available without strings attached lies in the fact that it comes with an extremely pronounced and unbendable bias. That bias states that all vehicles moving along the public roads must keep to the right side of the road.

If this system wasn't calibrated in such a way, it would be impossible to offer the amenities for conducting the public traffic.

So we see that the utmost flexibility of an infinitely complex system, such as public traffic, is only possible if that system is heavily calibrated in a non-negotiable fashion.

And because that calibration is non-negotiable, it does not qualify as being called a contract. In other words, if you're driving your car down the road, you're not holding the traffic contract in your hands that outlines all the details that bind you and the road owner. The road owner (i.e. the public) dictates the rules, and does so unilaterally. You have no say in whether you accept to keep to the right side of the road while driving. You simply must obey the unilateral rule, or suffer the consequences.

To put it more mildly, you must 'get used to it'.

Same principles apply when you're 'driving' around the web. The web specifies upfront the non-bendable rules and regulations, and you have no say in whether you like them, don't like them, whether you're planning to obey them or disobey them. The web doesn't expect you to make your stance known, and the web absolutely doesn't care.

Because of this unilateral set of rules, there cannot be a contract between the sever software on the web and the web client.

The Web is Uncoupled

Because of the lack of a bilateral contract between a web server and a web client, it is not possible to talk about any form of coupling on the web. Tight or loose coupling, which are terms tied with the world of software vendors' applications, lose any meaning on the web.

There are two reasons for this change:

1. On the web, the server need not know anything about the client
2. On the web, the server is blissfully unaware of the existence of any other server

All that is known on the web is that it is a sprawling collection of resources; these resources are easily accessible via the publicly vetted protocol (i.e. URI), and these resources know how to represent themselves and how to make their own state transition upon request.

Thanks to this particular bias, the web is the most scalable, the most interoperable, and the most robust, resilient and comprehensive computing platform ever.