• Bill Gates does his last CES Keynote, and we announce a PC that looks like a purse?
• News that Warner Brothers is going exclusively Blu-Ray is disappointing. However, I’m convinced that neither side will win this format war but that online downloads will trump both. Obviously, XBLM is a significant player in this space, but the market is crowding up quickly. Netflix apparently will unveil a new set-top box @ CES to let you watch HD movies via the Internet.
• Don Syme has a roundup of posts by John Liao about F#. Mostly, WPF + F# with a couple of ASP.NET 2.0 posts and one on XML .
• Speaking of F#, Stephan Tolksdorf has been working on an F# port of MS Research’s Parsec library called FParsec. Parsec is a “monadic parser combinator library”, something I have little experience with, so I’ve gone back to some source research on the topic, which I hope to blog at length about soon.
• Steve Vinoski talks about serendipitous reuse in his latest Internet Computing article. I’m not a believer in reuse in the enterprise, serendipitous or otherwise, but I liked the conclusion to Steve’s article when he wrote “It’s highly ironic that many enterprise architects seek to impose centralized control over their distributed organizations. In many cases, such centralization is a sure recipe for failure.” Also, his point that “control without controlling” works sounds vaguely familiar.
• Update: This is really Morning Coffee 136, but I don’t want to change the title since it’s part of the URL

Thanks to Technorati, I found this post by John Heintz. He’s checking out John Evdemon’se-book on SOA and has a problem with this overview:

SOA is an architectural approach to creating systems built from autonomous services. With SOA, integration becomes forethought rather than afterthought. This book introduces a set of architectural capabilities, and explores them in subsequent chapters.

To which John H. responds:

I, for one, would rather build on an architecture that promotes integration as an afterthought, so I don’t have to think about it before hand!!!

Yeah, I’d rather not have to think about integration before hand either. On the other hand, I want integration that actually works. It sounds like John H. is suggesting here that REST somehow eliminates the need to consider integration up front. It doesn’t. Consider this: if you’re building a Web 2.0 site then you are expected to expose everything in your site via APP, RSS and/or RESTful POX services. In other words, the Web 2.0 community expects you to have the forethought to enable integration. If you don’t, Marc Canter will call you out in front of Bill Gates and Tim O’Reilly.

This integration by afterthought approach seems to be big among RESTifarians. John H. links to a REST discussion post by Nick Gall advocating the principle of generality, “unexpected reuse” and “design for serendipity”. Money quote:

The Internet and the Web are paradigms of Serendipity-Oriented Architectures. Why? Largely because of their simple generality. It is my belief that generality is one of the major enablers of serendipity. So here I immodestly offer Gall’s General Principle of Serendipity: “Just as generality of knowledge is the key to serendipitous discovery, generality of purpose is the key to serendipitous (re)use.”

Serendipity means “the accidental discovery of something pleasant, valuable, or useful“. “Serendipitous reuse” sounds an awful lot like accidental reuse. Most enterprises have been there, done that and have nothing to show for their efforts or $$$ except the team t-shirt. Yet Tim Berners-Lee believes “Unexpected reuse is the value of the web” and Roy Fielding tells us to “Engineer for serendipity”. What gives?

First off, enterprises aren’t interested in unexpected or serendipitous reuse. They want their reuse to be systematic and predictable. The likelihood of serendipitous reuse is directly related to the number of potential reusers. But the number of potential reusers inside the enterprise is dramatically smaller than out on the public Internet. That brings the chance for serendipitous reuse inside the enterprise to nearly zero.

Second, enterprise systems aren’t exactly known for their “simple generality”. If Nick’s right that “generality of purpose is the key to serendipitous (re)use”, then enterprises might as well give up on serendipitous reuse right now. As I said last year, it’s a question of context. Context is specifics, the opposite of generality. Different business units have different business practices, different geographies have different laws, different markets have different competitors, etc. If an enterprise operates in multiple contexts – and most do - enterprise solutions have to take them into account. Those different contexts prevent you from building usable – much less reusable – general solutions.

Finally, I think the amount of serendipitous reuse in REST is overstated. If you build an app on the Facebook Platform, can you use it on MySpace? Nope. If you build an app that uses the Flickr services, will it work with Picasa Web Albums? Nope. Of course, there are exceptions – pretty much everyone supports the MetaWeblog API – but those exceptions seem few and far between to me. Furthermore, the bits that are getting reused – such as identifier, format and protocol – are infrastructure capabilities more suitable to reuse anyway. Serendipitously reusing infrastructure capabilities is much easier than serendipitously reusing business capabilities, REST or not.

The problems that stand in the way of reuse aren’t technology ones. Furthermore, the reuse problems face by enterprises are very different than ones faced by Web 2.0 companies. REST is a great approach, but it isn’t a one-size-fits-all technology solution that magically relegates integration and reuse to “afterthought” status. Serendipity is nice, when it happens. However, by definition it’s not something you can depend on.

Via Larkware and InfoQ, I discovered a great post on code reuse by Dennis Forbes: Internal Code Reuse Considered Dangerous. I’ve written about reuse before, albeit in the context of services. But where I wrote about the impact of context on reuse (high context == low or no reuse), Dennis focused on the idea of accidental reuse. Here’s the money quote from Dennis:

Code reuse doesn’t happen by accident, or as an incidental – reusable code is designed and developed to be generalized reusable code. Code reuse as a by-product of project development, usually the way organizations attempt to pursue it, is almost always detrimental to both the project and anyone tasked with reusing the code in the future. [Emphasis in original]

I’ve seen many initiatives of varying “officialness” to identify and produce reusable code assets over the years, both inside and outside Microsoft. Dennis’ point that code has to be specifically designed to be reusable is right on the money. Accidental code (or service) reuse just doesn’t happen. Dennis goes so far as to describe such efforts as “almost always detrimental to both the project and anyone tasked with reusing the code in the future”.

One of the more recent code reuse efforts I’ve seen went so far as to identify a reusable asset lifecycle model. While it was fairly detailed at the lifecycle steps that came after said asset came into existence, it was maddeningly vague as to how these reusable assets got built in the first place. The lifecycle said that a reusable asset “comes into existence during the planning phases”. That’s EA-speak for “and then a miracle happens”.

Obviously, the hard part about reusable assets is designing and building them in the first place. So the fact that they skimped on this part of the lifecycle made it very clear they had no chance of success with the project. I shot back the following questions, but never got a response. If you are attempting such a reuse effort, I’d strongly advise answering these questions first:

• How does a project know a given asset is reusable?
• How does a project design a given asset to be reusable?
• How do you incent (incentivize?) a project to invest the extra resources (time, people, money) in takes to generalize an asset to be reusable?

And to steal one from Dennis:

• What, realistically, would competitors and new entrants in the field offer for a given reusable asset?

Carl Lewis wonders Is your code worthless? As a reusable asset, probably yes.

Yesterday, I posted about services and reuse. More to the point, I posted why I don’t believe that business services will be reusable, any more than business objects were reusable. However, “can’t reuse business services” isn’t the whole story, because I believe in different kinds of reuse.

The kind of reuse I was writing about yesterday is typically referred to as “black box reuse”. The idea being that I can reuse the item (object or service) with little or no understanding of how it works. Thomas Beck wrote about colored boxes on his blog yesterday. Context impacts reuse – the environments in which you plan to reuse an item must be compatible with what the item expects. However, those contextual requirements aren’t written down anywhere – at least, they’re not encoded anywhere in the item’s interface. Those contextual requirements are buried in the code – the code you’re not supposed to look at because we’re striving for black box reuse. Opaque Requirements == No Possibility of Reuse.

As I wrote yesterday, David Chappell tears this type of reuse apart fairly adeptly. Money quote: “Creating services that can be reused requires predicting the future”. But black box reuse this isn’t the only kind of reuse. It’s attractive, since it’s simple. At least it would be, if it actually worked. So what kind of reuse doesn’t require predicting the future?

Refactoring.

I realize most people probably don’t consider refactoring to be reuse. But let’s take a look at the official definition from refactoring.com:

Refactoring is a disciplined technique for restructuring an existing body of code, altering its internal structure without changing its external behavior. Its heart is a series of small behavior preserving transformations. Each transformation (called a ‘refactoring’) does little, but a sequence of transformations can produce a significant restructuring. Since each refactoring is small, it’s less likely to go wrong. The system is also kept fully working after each small refactoring, reducing the chances that a system can get seriously broken during the restructuring

Two things about this definition imply reuse. First, refactoring is “restructuring an existing body of code”. It’s not rewriting that existing body of code. You may be making changes to the code – this certainly isn’t black box reuse – but you’re not scrapping the code completely and starting over. Second, refactoring is making changes to the code “without changing its external behavior”. You care about the code’s external behavior because somewhere, some other code is calling the code you’re refactoring. Some other existing piece of code that you don’t want to change – i.e. that you want to reuse.

When you refactor, you still reuse a significant amount of the code, but you’re not having to predict the future to do it. Refactoring**is the kind of reuse I believe in.

In his article, David talks about types of reuse such as business agility, adaptability and easily changeable orchestration. These look a lot more like refactoring than black box reuse to me. Unfortunately, David waves these away, saying  “Still, isn’t this just another form of reuse?”. Reconfiguration hardly qualifies as “predict the future” style reuse that he spends the rest of the article arguing against. It’s just one paragraph in an otherwise splendid article, so I’ll give him a pass this time. (I’m sure he’s relieved.)

A couple of weeks ago, David Chappell posted a great article on SOA and the Reality of Reuse. When someone mentions the idea of using SOA for reuse, I cringe. David does a great job blowing the “SOA for Reuse” argument out of the water. In the future, I will just send that link rather than spending the time arguing out the point.

But something nagged at the back of my brain about that post. David starts by talking about object reuse before making the parallel to services. The problem with that comparison is that object reuse hasn’t been a failure. When was the last time you wrote a String class? A Linked List? A Button? There’s been support for Buttons in Windows since at least the 3.x days (probably longer, but that’s before my time). Whatever your OO language of choice, there’s a big collection of reusable objects to go with it.

Given his position as “famous technology author”, I’m assuming David is well aware of successes of object reuse. Furthermore, I doubt it was an accident that in his article he writes that “reuse of business objects failed” (emphasis added). While there has been success around object reuse, essentially none of those successes have been in a business scenario. In fact, there have been some high profile projects such as Microsoft’s Business Framework and IBM’s San Francisco Project that have crashed and burned been significantly less than successful.

So here’s the question: given that general object reuse has seen some success, what’s so different about business objects that causes reuse to fail utterly? Since we’re really interested in service reuse, knowing why some object reuse succeeds and other reuse fails will help us understand which services are likely to be reusable and which wont. I would say that success of object reuse hinges on context.

Wikipedia gives this definition of context: “The context of an event, word, paradigm, change or other reality includes the circumstances and conditions which surround it.” (emphasis in original) For example, the word “order” is ambiguous. If you’re using a procurement system for the military, you could conceivably be given an order to place an order. (OK, that’s silly. But you get the idea.) The word “order” has two different meanings. However, the words that surround the ambiguous term make the meaning clear. An order that you place is different that an order that you give. That’s context.

A string or a linked list or a button has very little in the way of contextual needs. That is to say you can use it the exact same way in a wide variety of environments. A business object on the other hand has significant contextual requirements, which makes reuse difficult or impossible. For example, a Purchase Order object from the above-mentioned military procurement system sounds like it might be reusable. At least until you take into account the differences between branches of the military, between ordering tanks and ordering uniforms, between active units and reserve units, etc. Once the generic Purchase Order has been specialized to the point of practical usability for a given scenario, it’s no longer reusable in the general case.

Taking this back to the service realm, likewise I figure the reusable services will be the ones with little or no contextual needs. A good example is the identity and directory services such as Active Directory and its competitors. Sure, you use LDAP not SOAP to access it, but AD is certainly both reusable and a service plus it’s in wide usage. Other candidates for reusable services my team is looking at are service directory, management and operations, business activity monitoring and provisioning.

I actually think there will be less reuse in services than there was with objects. The value of reuse of services has to exceed not only the contextual issues but also the overhead of distributed access. Calling across the network is an expensive operation – whatever’s on the other side better be worth the drive. I’m guessing for services, more often than not, reuse won’t be worth the trip (if it’s possible at all).

Update: David pointed out to me that the last paragraph of his article begins:

Object reuse has been successful in some areas. The large class libraries in J2EE and the .NET Framework are perhaps the most important examples of this.

Doh! I guess my “assumption” that David is aware of successful object reuse was correct.