Sergey Beryozkin, a former coworker at IONA, has posted some questions specifically for me. Questions are good; it’s almost like being interviewed, and it’s certainly better than being called sad and depressing! Let’s see if I can provide some answers.
But first, I want to address something I keep hearing when I post things like the answers below: “Steve, you’ve changed your whole story ever since you left IONA!” While the technical opinions I’ve been expressing in this new blog might seem shocking since they seem different from what I used to say, they’ve actually been under development for a long time. What actually happened is
- My technical opinions changed gradually over the course of 5 or 6 years while I was still at IONA.
- I finally chose to leave because my preferred technical direction had diverged significantly from where IONA was going.
- I left when I did because of a wonderful opportunity that came up at a new place where I could put all my latest ideas to work. So far, it’s all I hoped it would be, and more.
- I couldn’t publicly blog about my new opinions, write about them in my column, or present them at conferences until after I had changed jobs, for obvious reasons.
If you had enough time and patience to read through all my IC columns, you’d certainly find plenty of evidence that my thinking about all this stuff had already been changing for years prior to my departure from IONA. I hope this clears things up for those of you who mistakenly think I’ve just done an abrupt about-face.
Now, on to Sergey’s questions:
1. Do you think client code generation is evil ? If yes, do you expect people to do manual programming on a large scale ?
In days long gone by, code generation clearly helped us get a grip on certain types of distributed systems, and make advances as a result. But since then we’ve learned that you can’t pretend a distributed system is a local one, that RPC is less than desirable, and all kinds of other lessons.
All in all, I am now of the opinion that it’s generally best to avoid distributed system development based on language-first approaches (unless it’s a language like Erlang where distribution is effectively built in, but even then you still can’t ignore distribution issues). Code generation is based on the notion that I want to develop my distributed system using the idioms and practices of my programming language, which I now believe is almost always wrong. If you avoid specialized interfaces and use a uniform interface instead, it significantly reduces the need for code generation. On top of that, using standard MIME types for exchanged data rather than making up your own data types in WSDL or Java pretty much eliminates the need for code generation in many cases, IMO.
Now, I have to say that your question seems to imply that code generation is required for large-scale development. I don’t see why that would be the case. “Manual” programming isn’t much of a chore when you choose the right language.
People seem to get really upset when I say that the static typing benefits of popular imperative languages are greatly exaggerated, and when I say that developing real, working systems in dynamic languages is not only possible, it’s preferable. I usually find that, coincidentally, those are the same people who’ve never honestly tried the alternatives. Some who actually do try the alternatives do so by trying to use the new language exactly the same way they use their favorite language, and when they fail for what should be obvious reasons, they blame the new language.
2. If code generation is acceptable, would you welcome WADL? If yes, what to do with generated client types with respect to the change management ?
I’ve personally never encountered a need for WADL, but that’s just my opinion and experience. Marc Hadley and others obviously find it useful, and the RESTful Web Services book promotes it, and they’re all smart folks, so maybe there’s something to it.
Either way, no interface definition language is ever going to keep you or some other real live person from having to figure out what the service actually does and how to actually use it, and then coding your client accordingly. Normally you figure out that sort of thing by reading some sort of human-readable document, not just by looking at WSDL, WADL, or any other IDL. So if you have to read a document, and you’re avoiding code generation thanks to the uniform interface and the use of standard data formats, why bother with any IDL?
3. Do you think the idea of interfaces is broken ? Do you see any point in creating minimalistic yet not generic interfaces with encouraging users to focus on data ?
I believe that it’s important to avoid specialized interfaces whenever possible and prefer a uniform interface instead. Interface specialization, even of the minimal variety you mention, inhibits reuse. My Jan/Feb ’08 IC column, which is not yet published but is already written, covers this in detail.
4. Would you expect in the future even software modules interacting with each other through a common generic interfaces ?
I assume you’re referring to modules residing together within a single address space. To some extent that’s already been happening for years, thanks to frameworks, which of course are also based on interface uniformity. But will we ever get to the point in the foreseeable future where all entities residing within a single address all have the same generic interface? No.
Remember, REST is an example of applying well-chosen constraints to achieve desired architectural properties for a broad class of distributed systems, and so that’s what its constraints are all about. It might be an interesting brain game to consider what properties REST’s constraints could induce within a non-distributed system, but I’m not sure the exercise would be of any practical benefit.
5. “WS-* was simply not worth it to any customer or to me” – was it not ?
The customers that I saw benefit from WS-related technology gained those benefits only because of IONA-specific innovations that were not part of WS-*. In general, WS-* didn’t do anything for them that wasn’t already possible with prior technologies.
6. Do you think WS-Policy is a useless technology ?
I personally have no use for it.
7. Do you think AtomPub is the best way to do REST ? Is AtomPub better than SOAP ?
AtomPub fits a particular class of problems, but it targets only a subset of what REST can be applied to, so it doesn’t solve everything (and neither does REST, of course). I don’t believe AtomPub and SOAP are directly comparable, but I personally haven’t found a use for SOAP, other than when I’m forced to talk to systems that offer only SOAP-based interfaces.
In 1999-2000 I thought SOAP was finally going to help glue the CORBA and COM worlds together and make for a happy integrated place. But as I learned more and more about REST, starting at roughly the same time, I saw the light that SOAP was missing the boat, big time, by abusing HTTP.
8. What is a better way to protect investments made into WS-* ? Throw them away and start from scratch or start embracing the WEB while improving on what can be done with WS-* ?
I’m not sure there’s a general answer to this question, as it’s not really a technical question and it depends too much on particular business situations. Personally, if my current job involved WS-*-based systems that I had any say over, I’d throw them away, but I’m in a startup and we could easily do that. Thankfully, though, we have no such systems.
9. Do you think an “integration” problem IONA has been so good at is an “overblown” problem ?
I think that in the whole scheme of things the integration problems that IONA is good at solving are not very common. Nevertheless, those problems are very real; that’s IONA’s niche, and they’re great at solving them. The very bright developers, customer engineers, and sales engineers at IONA regularly come up with wonderful well-engineered and budget-pleasing solutions when nobody else in the industry can. But if you work in that environment day after day, it’s only natural that you might start to think that all integration problems look like those uncommonly difficult ones. In the big picture, that’s just not the case.
10. Can you please, if possible, describe a bit what kind of (software) clients will use your RESTful systems, (Web)UI tools or client software modules pushing the data up the response chain ?
In general, the company I work for is in stealth mode, so there’s virtually nothing I can tell you. But I will say that when you’re building RESTful resources, you tend not to think of the browser and other client software differently — they’re both just clients. If you’re primarily doing Web development and maybe sprinkling in some support for programmatic clients for good measure, that’s different. Either way, anti-REST folks commonly claim that REST’s success is due only to the fact that there’s a human-driven browser in the mix, but that’s one of the dumbest things I’ve ever heard.
11. What is the difference between service factories found in Corba and RESTful services creating new child resources as part of POST (as far as managing child resources is concerned) ?
As far as managing child resources is concerned, the difference is that CORBA has no uniform interfaces or data representations. The CORBA client therefore has to be specifically coded to be able to manage the newly-created resource.
12. Do you always prefer dealing with fine-grained resources ?