Thursday, August 16, 2007

Why is ROA Hard to Understand?

Resource Oriented Architecture is the term I've coined a year ago, only to discover almost immediately afterwards that others have been thinking independently along the same lines. During the past 12 months, I've witnessed numerous discussion threads and debates centered around the importance of ROA. Most of these discussion threads belie complete misunderstanding of the Resource Oriented Architecture, which is very alarming, given that ROA is the native architecture of the web.

And web is the native infrastructure for information dissemination, exchange, and sharing.

Old habits die hard

Most software developers in circulation today have cut their teeth by learning how to implement computing algorithms. Something akin to: "here is a jumbled sequence of numbers, write a computer program that will sort them in ascending order".

The emphasis in such an exercise is always on exhibiting reasonable amount of direct control over the execution logic. The would-be programmers have been groomed for generations to master the skills of gaining full control over the stream of instructions that the CPU executes. In other words, to be a computer programmer/software developer implies to them that a full control over all the processing aspects must be in place.

It's a single point of human control, same as it's a single point of machine control (i.e. the Central Processing Unit, or CPU).

But in the world of the web, such notions of centralized control are not only ridiculous, they are down right harmful. Still, armies of CPU-trained programmers have now been employed and deployed to develop software that will run on the web.

Is it a small wonder then that such 'central point of control' minded individuals are creating fully dysfunctional web sites? Indeed, old habits do die hard.

New habits are slow to emerge

What the above described situation then means is that the existing workforce that is dedicated to developing software programs is pretty much a write-off. Because old habits die hard, it is quite likely that it will be much harder to unlearn the old habits and relearn the new ones, than to start from a clean slate.

However, given the vast demand for web-based software that is out there, we must work on creating some sort of a compromise, in the attempt to bring the crusty old 'central point of control' software development workforce into the web fold. For that reason, we need to continue explaining the difference between the Central Processing Unit software architecture, and the Resource Oriented Architecture.

Transitioning from doing to managing

One of the hardest things to do in life is to make a successful transition from doing something to managing that same thing. The temptation to roll up one's sleeves while managing the process is simply too strong to resist. And that's why not too many people end up being good management material.

In the world of software development, right now there is a huge demand for people who are capable of abstaining from rolling up their sleeves and instead delegating the responsibilities to the 'workforce' out there.

What does that mean? In a more technical parlance, it's been proven that once software developers get trained in making procedure calls when attempting to process some information, they tend to get addicted to that gateway drug. Similar to how to a person with a hammer everything looks like a nail, to a programmer who had learned how to make procedure calls, every information processing challenge looks like a string of procedure calls. This algorithmic frame of mind is very hard to get rid of, once a person gets it contracted. And in order to become an efficient web developer, each and every procedure-besotted person must learn to let go of the procedure call driven world view.

Transitioning from local to distributed procedure calls

Most people learn how to program computers by implementing procedure calls that are local. What that means is that their world view is CPU-centric. In other words, the executable code in its entirety is sitting on a local box, usually right next to the developer's desk. The developer then intuitively grasps the world as consisting of a single Central Processing Unit which acts as a traffic cop, deciding on who gets to do what and when. The 'who' in the previous sentence refers to the procedure. Typically, a programmer will modularize his code into a fairly large number of procedures. These procedures will then be called at opportune moments, will perform the intended processing, and will then recede in the background.

This situation is the prescribed way for teaching newcomers how to develop software. It willfully ignores the real world issues, such as that there is very little use and need in having a 'desert island', 'single sink' scenario, where a computer user will be sitting alone engaged in the 'glass bead game' on the computer. In the world of business at least (and also in the world of entertainment), multiple users are a must. Meaning, CPUs and people will be networked (999 times out of 1,000).

There inevitably comes a time when a software developer wannabe realizes that a transition from a single CPU to multiple CPUs connected via the network, is unavoidable. At that point, the newbie usually gets struck by the immense complexities that such transition entails. And it is at that point that the newbies all over the world decide to drag in the procedure call world view into the networked world.

Now the problem of control in a multi-CPU environment arises. Who's in charge here? It used to be that a single human mind was in full charge and control over the execution of computing instructions, via the single CPU. Now, all of a sudden, multiple CPUs which are distributed across vast networks enter into the equation. The remote nodes start posing the problem when it comes to controlling the proceedings.

The only way for such developers to try and tame this complexity is to wiggle in their chairs and to fabricate some hairy-brained scheme for enabling remote procedure calls (or, RPC). Various mind-boggling protocols get implemented (CORBA, RMI, DCOM, SOAP, SOA, etc.) All of these protocols are incredibly arbitrary, non-compelling, frighteningly complex and brittle.

As we can see, this transition from making local, simple-minded procedure calls to making distributed, remote procedure calls never goes well. In the end, it inevitably results in fragile, brittle software that requires constant duct-taping and chewing-gumming in order to stay afloat.

Who's going down with the ship?

It is obvious to even a casual observer that the majority of software projects, today as in the past, fail miserably. As the complexities of the business scenarios continue to increase at a frightening rate, this rate of failure will only skyrocket.

At this pace, it won't be long before the software development industry turns into another Titanic, if the majority of developers continue to charge down the remote procedure call path. Developers who refuse to go down with the ship have only one option -- abandon the RPC ship and hop into the ROA boat.

But as we've already seen, the transition from navigating a huge, unwieldy ship to rowing a tiny nimble ROA canoe is proving more challenging than most developers are prepared to bear. That's why there must lie a major shakeout ahead of us, a shakeout that will separate the monolithic totalitarian software practices from the nimble, distributed ones. And ROA practices are certainly on the opposite side of the monolithic remote procedure calls practices.

How to make the transition?

It seems to me that, in the process of making the transition from RPC to ROA, the biggest stumbling block for the entrenched software developers lies in the fact that ROA proposes erecting an impenetrable barrier between the client and the resourses on the server. In the bad old RPC world, such barriers are unheard of. In other words, if the client is privy to the protocol that the service-oriented server had arbitrarily and unilaterally made up, the client can intimately manipulate the state of the server.

No such thing is ever possible in the ROA world. And that's the biggest put off for the honest-to-god procedural crowd. They simply don't seem physically capable of conceiving the world where it would not be possible to 'crack the code', learn the protocol, and then rule the server on the other end.

So in order to make a successful transition to ROA, these software dictators must learn how to abdicate from their dictatorial throne. What are the chances of that happening en masse any time soon?

Slim to none? What do you think?

Wednesday, August 15, 2007

Resource Representation

Software developers seem largely incapable of understanding the difference between resources and their representation. Understanding that difference is absolutely vital in understanding REST and the Resource Oriented Architecture (ROA).

Is it a small wonder then that we are beginning to see articles like this one ("Why is REST so hard to understand?") pop up in the publications devoted to the web architecture? It is absolutely clear that we won't be in the position to advance ROA practices unless we reach a critical mass of people who do possess a solid grasp of what is the difference between a resource and its representations.

Right now, it seems like only an infinitesimally small percentage of software developers are aware of the significance of that difference. For example, if we say that there are ten million software developers worldwide, 9,999,000 of these developers are blissfully ignorant that such a thing as resources and their representation even exists. Which leaves us with only about 1,000 developers who truly understand what it all means. Not a very encouraging statistics. As a matter of fact, the situation today is right down dismal.

We need to do something quickly in order to remedy this catastrophic situation. My small contribution here is to attempt to clarify the difference between resources and their representation. I will use mostly concepts from everyday life for illustration purposes. I will then attempt to draw the parallel between these concepts and the concepts one encounters in the arena of software development.

What is a Resource?

Let's start from the top: a resource is anything that humans find useful. For example, a house might be a resource. Or, money might be a resource. We find houses very useful, because they offer certain level of comfort in our daily living. We also find money very useful, because it's a resource that enables us to get other resources, such as houses.

Ten years ago, when I was buying my first house, I wanted to see what kind of a house can I afford. To that end I met with a mortgage broker, who interviewed me in the attempt to assess my buying power. Among other things, he needed to know how much money can I allocate towards the down payment on the house.

Once I told him how much money I have for the down payment, he was able to plug that information into his spreadsheet and then tell me what kind of mortgage do I qualify for. So I was then all set to go out and shop for the house, right?

Well, not so fast! Just because I've blurted out a dollar figure that I had in mind for the down payment, didn't automatically mean that I fully qualify for that mortgage. Because, you see, my word in these matters was viewed as being largely subjective, that is, prone to miscalculations and all kinds of other aberrations. What the bank needed is a more objective assessment of my buying power. Talk is cheap, and anyone can claim that they have one hundred thousand dollars tucked away in their bank account, ready to be plopped in toward the down payment, but the reality might be somewhat different.

Because of that, the banks have devised a more impartial practice, whereby the applicant must provide what is deemed to be a more objective proof that the money really is in the applicant's bank account.

In this example, the money that has been allocated for the down payment on the house is regarded as a resource.

What is a Representation?

Now, the down payment money we are talking about may indeed be sitting in my bank account. But how am I to truly convince the mortgage broker that it is really there? Well, I use the means of representation, that is to say, I use something else that acts on behalf of that money. For example, I use my words to convey the fact that I do have $100,000 in my bank account. My words then represent my money.

But, as we've seen, that representation (my words uttered in a casual conversation) is apparently not good enough for the mortgage broker. He needs something more 'solid' before he is fully convinced that the money is actually there. Meaning, he needs a different form of representation.

Typically, what the mortgage broker would deem a fairly impartial and objective representation of my money is a piece of paper issued by my bank that claims that it is true that I do have $100,000 in my account. In other words, once the mortgage broker receives that piece of paper, he can 'take it to the bank', so to speak.

That piece of paper is what we call a representation of a resource. The real money is nowhere to be found in that representation, yet in a somewhat superstitious manner, all the parties involved almost religiously obey and agree that a piece of paper is as good as the real thing.

Back on the Web

The exact same protocol abides on the web. There, as in everyday, non-virtual life, we have resources which are tucked away somewhere, and all we get to see, feel and touch are the representations. Resources on the web are merely concepts that are being represented using other concepts. On the web, as in real life, no one ever gets to see, hear, feel and touch a resource. All we get is mere representations.

We are free to attempt to manipulate those representations. And even in the cases when our manipulation yields perceptible differences, we have no grounds to claim the we have actually manipulated the resource itself. All we can conclude is that the resource representation has changed under the influence of our actions, nothing more, nothing less.

For example, if there is a resource such as a volleyball tournament published on the web, I can get its representation by sending a request for it. I may then decide to destroy that tournament by manipulating the tournament's representation. And my action may result in an affirmative representation (i.e. the resource may respond by sending me its representation which states that it has destroyed itself). I may then conclude that the volleyball tournament has, indeed, been destroyed. But I really have no way of ascertaining that. All I can claim is that I have acted upon the initial representation of that volleyball tournament, I have sent it the request to destroy itself, and I have received the confirmation that it is now destroyed. However, the resource itself may still be alive and well, existing somewhere beyond the reach of the resource representation. The only thing that is manifestly certain is that from that moment on, the resource will refuse to render its representation for the incoming requests.

This is similar to how, in the real world, no one would ever suggest that I take the mortgage broker into my bank's safety vault and point him to the pile of cash that's sitting there, and tell him: "Here, here's my $100,000, please count them and let's get on with it!" No one goes straight to the resource itself in real life, and the same holds true in the digital life as it gets distributed on the web (not to mention that even the physical cash is merely a representation of some other concept, etc.; one can never possibly get to the bottom of it, that is, the real resource is nouminal, unreachable by us mere mortals).

Understanding this distinction is vitally important if we are to move forward successfully in building the functional web of information. It is my experience that none of the developers I've ever worked with understand this situation, and that all of them erroneously believe that they are, at all times, working with the 'real thing'. Nothing could be farther from the truth, so I implore all developers to take a moment and try to digest the difference between resources and their representations.