Human-Powered Web Services
As SOA has become a more mainstream IT concept... you might even say a more mundane IT concept... there has been a lot of thought put forth on the creation of Composite Applications.... collections of distinct Services that are orchestrated and choreographed together (using BPM technologies) to implement some "higher-level" business functionality.
Many of these Composite Applications need user-interfaces, just like "normal" applications, but fortunately the transition from building a UI on top of objects (often EJBs) to building a UI on top of Services (often Web Services) is generally not that hard for programmers to make. Perhaps the biggest adjustment is in moving from a world where pass-by-reference was possible to a message-oriented world where everything is pass-by-value... but that's not really much of an obstacle for good programmers.
A more subtle aspect of user-interfaces and Composite Applications becomes apparent when you start to consider the Services that make up the applications. Most of the folks that I talk with tend to think of Services as automatons... fully automated tasks carried out by machines. This is especially true when I use the term Web Services... Everybody knows that a Web Service has nothing to do with people, it's just a machine at the "other" end of the line.
I'm going to suggest that conceptually limiting Web Services to automatons is a mistake that has hampered our ability to benefit from all that SOA has to offer. Our shared belief that Web Services are "always" automatons has impacted our conception of Composite Applications and has even impacted the design of most of our development environments (IDEs).
That's a pretty strong statement, so I'd better try to explain myself. Perhaps an example is in order....
Let's say that you are building a Composite Application to process an Order of some sort. Also assume that your customers speak many languages, and that it's necessary to translate each order to a common language before it is processed. To make this process pretty darn simple, let's also assume that Services are available to translate the orders from one language to another. Piece of cake... just funnel the order through the Language Translation Service and you're done.
Any good Service-Oriented IDE (such as NetBeans with the Enterprise Pack ) can handle the above process with ease. The IDE's tools make it relatively simple to orchestrate the process using BPEL, and relatively simple to build a UI on top of the BPEL (it's a Web Service after all). In short-order, you've created your Composite Application and all is well in the world.
So where's the beef? What's wrong with this picture?
Nothing really... until you start to consider the creation of the Language Translation Service with your IDE. Our conception of Web Services as automatons causes few problems when consuming the Services, the problem becomes evident when creating them.
I picked Language Translation on purpose... It's hard. Go out to any of the free translation services, translate this page to another language and back again, and you will see what I mean. Language Translation (at this point in time) is better performed by a person than by a machine.
Here's the previous paragraph translated to Spanish and back to English:
"I chose the translation of the language in intentionâ€¦ He is hard. Leave to the free services of translation uces of, again translate this page to another language and posteriora part, and you will see what I mean. The translation of the language (to this point in time) is made better by a person than by a machine."
So back to my example... Let's assume that the Language Translation Service is best performed by a Human (at this point in time). We still want a Web Service interface... we want to be able to consume this Service from within any Composite Application (and not change our application if at some point in the future machine translation becomes better)... but we also need a human-oriented interface for the person who is actually going to translate the Order.
Try building a Human-Powered Web Service with your IDE. You can do it, but it's tough. You're going to have to cobble together something that links together a human-oriented application with a Web Service, and it's probably not going to be pretty. This "ugliness" really shouldn't be a big surprise, because we've never thought of doing such a thing (maybe "never" is a bit strong... but not very often).
Now that I am spending much more time as a Business Process Guy, I'm finding the need for Human-Powered (Web) Services isn't rare at all. All of the good BPM suites (like Lombardi and Fuego) erase most of the distinctions between creating Human-Powered Services and creating Autonomous Services because most business processes are a mix of both types of Services.
Unfortunately, at this time there aren't widely-adopted standards for Human-Powered Services (HPS)... the BPM suites are proprietary and the concept of a "stand-alone" HPS seems alien. There's a good reason for that... when an HPS is invoked, the Human has to "know" that there is work to be done and that implies a notification mechanism like a task list or email.
I don't want to imply that it will be "easy" to come up with standards for Human-Powered Services... just look at all of the turmoil surrounding "BPEL for People"... but it is time for us to start addressing this class of Service in our IDEs. In this blog entry I have focused mostly on the creation of the HPS... but there are also some issues of consumption (people tend to be much slower than machines).
What it all really boils down to is wider awareness of Process-Oriented concerns... business processes are made up of automated and human-performed tasks, and we need to be able to implement both types of tasks in a manner that allows them to be consumed by a multitude of applications. That's what SOA was really all about in the first place.
(cross-posted at Thoughtful Programmer)