The value of principled design – REST is just one example

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.