Rajith’s Column

Mark Baker has hung up his boots on the REST vs SOAP debate. I appreciate his effort in building awareness about the value of REST and convincing people that it provides a solid basis for designing distributed systems. In the same post, Mark also says that, “The war really has been won”. Other REST folks including Stefan Tilkov says more or less the same thing too. I don’t know. In my humble opinion, a few years from now when the systems we design/build today using a RESTful, WS-* (or whatever) approach will show us which approach yields the better result in terms of scalability, extensibility, reliability, interoperability, flexibility, versioning, reusability ..etc. Sure the REST folks would say the web has being there for a while now and it works. But usually there is a human on the other side that drives the interaction. So it remains to be seen whether it will be the same with application-to-application interactions as well.
After all the hype surrounding REST,WS-* etc.. dies out and when people have enough experience building real world applications using both approaches and realizes the advantages and disadvantages of each approach there will be less debate as to which is better, or whether we need both approaches ..etc. The answers to these questions will become more clear to the ordinary folks in time. I for one will have an open mind and is very interested to see the outcome of all of this.

The REST vs SOAP debate has been more emotional/religious and less technical as of late. Several folks burned bridges due to insidious remarks, inflammatory comments and even personal attacks. Irrespective of the technical merits one should be able to tolerate/appreciate differences of opinions and debate in a more disciplined manner than resorting to personal attacks or inflammatory comments. Even if you are the most intelligent person in the world it doesn’t matter if you can’t put forward your technical arguments without degrading your own self by making inflammatory comments or personal attacks.

To me the value of Roy Fielding’s dissertation goes beyond REST. Steve Vinoksi summarised it very well in one of his comments while answering a comment I made on his blog.

It’s(Roy’s dissertation) not really primarily about REST; rather, it’s about principled design. Much of his dissertation is about architectural elements, principles, constraints, properties, and the relationships between them all. REST is used as a very clear example in chapter 5 of what principled design is all about.

Why can’t we use a principled design approach when we do SOA or for that matter any other architecture?

When we add contraints or relax constraints we induce certain properties in our architecture. As an architect you make an educated desision as to what constraints make sense in your environment and what doesn’t. When designing systems don’t we go through decisions like “should we make these services stateless or statefull ..etc” during our design meetings ?

I think in what ever system you design as an architect you should think through and note down the constraints you want to impose on your system. This will provide a proper foundation to your system and an excellent guideline to your developers which will clearly communicate the desired goals of your system. Then later on when somebody else wants to relax any of these constraints or add more constraints they already have a guideline and can see how the “relaxing of an existing constraint” or the “addition of a new constraint” can impact the overall system.

REST is just a name coined by Roy to identify a set of constraints, and they are not the only constraints, nor the best combination of constraints in every situation. As Steve mentioned Roy spends the first few chapters providing an excellent analysis about “architectural elements, principles, constraints, properties, and the relationships between them all” and of course the value of a principled design approach.
To me the value of Roy’s thesis goes beyond REST and I hope most people would realize the same.