What's the difference between DDD, TDD and BDD?

All three double D's are about how to approach your design. What drives you, how do you get started, what's your angle? How do you decide which classes to use? What are the dependencies, etc.

Domain Driven Design (DDD) focusses on the core model (the domain) and tries to keep other stuff like UI's and databases separate. You can google for the site and the Book from Evans. I'm not too convinced it offers much new, but maybe I'm influenced too much by the worst presentation of QCon (Filipe Rodrigues, better luck next time man). I also have a graduate which can't explain to me what the big deal is.

Test Driven Development (TDD) is the one I'm most familiar with from my XP classes. First code your JUnit test and then code your class to make it pass.

Behaviour Driven Development was new to me. I noticed they were talking about BDD in connection to Ruby (RSpec), but just stumbled across a nice page that explains the concept: http://dannorth.net/introducing-bdd. Even if you don't use BDD, it gives some really nice tips for TDD.

Head First

Some time ago O'Reilly came with a new series of books called "Head First xyz" with xyz being mostly about programming stuff (Java, Design Patterns, C#, ...). If you've looked at one of the books, you've seen they are different from the usual computer books. From the blurb:

"...Using the latest research in cognitive science and learning theory to craft a multi-sensory learning experience, Head First uses a visually rich format designed for the way your brain works, not a text-heavy approach that puts you to sleep."

This sounds mumbo-jumbo, but it's worked out as original books with lots of pictures, puzzles, scribbles and exercises. (Check the website for some samples: http://www.headfirstlabs.com/)As I had been curious about whether they are any good, I picked one up about Javascript. About halfway through I think it's funny and activating. It contains the right mix of text and pictures, explanation and exercises. Maybe it'll grow old if you read too many of these books, but it probably won't hurt a student to add Head First Java to his BlueJ book.

One final thing that struck me is the conversational tone they use in the book. Apparently this has been researched as adding to the learning experience. This is exactly the way I've written my study material from the day I came in de Hanze. I probably have some talent... :-)

Update: I laid my hands on "Head first Design Patterns" the other day and can recommend that one too.

QCon short recap

So, what do we make of all the information that was poured over us the last days? What is the most important? Of course, we will need to investigate all this stuff further. But at first outlook, I would say:

1. REST looks like an important new trend.
2. Erlang might answer the need for more Concurrent Oriented programming languages.
3. Java for enterprise applications is very much alive, also for real time systems.

Additional:
DSL's keeping turning up at conferences like these, but I don't really see what's the big deal. But maybe I'm missing some point.
Architecture is maturing, but there's no silver bullet.
Agile is maturing nicely, thank you.
Ruby on Rails fits nicely in their niche.
Domain Driven Development is a new term but nothing really new.

QCon Friday

And then it was Friday. Fatique was setting in, but we were determined to take it to the end. There were some really interesting tracks today.

The day started off with Randy Shoup talking about the architecture behind eBay. This was really architecture on the highest level. The amount of data/transactions/servers etc that ebay has is huge. An impressive talk, the slides are warmly recommended.

After that BBC talked about there architecture to bring media (video) to their users. A nice talk (especially since they filled in for Twitter at the last moment) but they had the disadvantage of being preceded by eBay which was hard to match.

At the same time Bart was at a presentation about Haskell in the "programming languages of the future" track. That track covered a number of programming languages which might (or might not) be the next big thing, such as Scala, F# and Erlang. Saillant point is that Haskell has been around for a long time and was removed from our curriculum some 5 years ago. Bart said that the presentation about Haskell by some professor was the best he had seen at QCon. "Pure theatre."

After that we went to the presentation about Erlang, a new programming language that's especially suited for use with concurrency. The language is hot on the fashionlists and might become very relevant with the rise of multicore systems. Take a look at the slides when they are available. One to watch. Joe Armstrong (called "the nutty professor" by another participant) also wrote a book about it.

After that the long awaited Rails 2.0 track, which after one minute I knew wasn't really what I wanted. Dr Nic explained at length the changes from Rails 1.2.6 to 2.0.1, not really what a beginner is looking for. Still, there was something to be learnt about IDE's and participating in open source.

After that Jan scored a polo-shirt at JavaBlackBelt (missing the first prize, 10 books at the O'Reilly stand by just an inch) and we went back home. The delay wasn't too bad this time.

Termen

Wat te denken van
Pizza-graph
Living in the cloud
SQS
Deep Zoom
MUCK
ECC
KML
KANBAN
TTR
CQC
YAGNI
PAP
AHMLI
PID

Quotes of the day

Here some nice quotes of the speakers of today and yesterday:

"It's binding here, it's binding there, it's binding everywhere." (Mike Laulty)
"Powershell just rocks." (Eric Nelson)
"We now can make usefull data in the cloud." (Jonathan Trevor)
"Democracies do not always pick the right candidate."(David Anderson)
"Problems you are having, hmm? Making roles explicit you must." (Udi -Yoda- Dahan)
"London is a nice city." (Filipe Rodrigues)

QCon Thursday (1)

The day started off with a lecture by another famous name, Kent Beck, on developments in Agile. A good speaker, very American. It's all about accountability and transparency. IT and business are moving closer to eachother, IT has to be just as accountable as the business is used to be.

The next lecture was by Stefan Tilkov on REST and RESTful webapplications. As this was a new concept to me, I decided to listen in. A good talk, although I didn't completely understand it in one go. It seems REST is a set of 5 principles which you can apply when developing webapplications. This gives you a lot of technical possibilities. But as far as I can see it's an alternative to webservices. An important new trend already and we still haven't finished with the previous one.

Pete Goodcliffe talked about two systems. One with bad design and one with good. A bit of a standard talk, but he was entertaining and it's nice to see some points again. But Bart thought he could have done it better.

Giles Colborne tried to define the term op 'Simplicity' in User Interfaces. According to him it's not the same as usability. A bit dull, nothing special. But he did mention a number of "red flags" that made me think about the DOP immediately.

Rod Johnson (author of a famous J2EE book) talked about innovation in J2EE. At first impression, he came across as a annoying, stubborn American with a Texan drawl. Maybe that's what he is. But he knew his subject really well and brought a lot of interesting analogies to the subject. The slides are warmly recommended.

The last talk about Domain Driven Design is so bad that I can update the blog. A brazilian dude in very bad english who talks about stuff we all already know since we started our education. Pity, as there is a lot to be told about DDD.