Agile Architecture

by Paul Browne



The best thing about doing presentations is the questions you get asked at the end. Apart from the stomach churning moment of 'will I be able to answer this one?' they give you a new angle on things that you may have always assumed, but force you to think of in a different way.



Take one of the questions after yesterday's Enterprise java presentation at DCU. One of the topics mentioned in the final 'putting it all together' was the Agile and RUP (or other upfront design) methodologies. The question , coming from an attendee that was keen on using Agile , was 'How do you do Architecture in an Agile project?'


DCU Logo


On the face of it this seems a contradiction. Agile in it's most extreme form is 'make up just enough design as you go along', with automated tests to make sure changing things later is a relatively low cost and pain free process. In real life most projects are a balance between Agile and need some element of a more formal process (often trying to answer the question 'how mucn is this going to cost?)'


So , how do you merge Agile with an upfront design process? It's easier than you think.


Most systems built the 'traditional way' do not get all their design done in one go. They might start out with the best of intentions for phase 1 with a clean sheet but over the months / years people come and go, business requirements change and different phases try to deliver different things. Over time the original clean design twists and turns and you work hard to try and make it work out ok. Some of features you thought were key may end up getting thrown out as too complicated.


Now Agile architecture is a similar situation. Each weekly / monthly iteration is like phases on the larger project , with twists and turns that may be unexpected. The difference now is that you have a safety net comprised of your (J)Unit tests, to allow you to make radical changes if your blueprint ends up in a cul-de sac.


Yes, it is ok to have an idea the bigger picture and where you like to go with the design. Yes, a good architect will find reasons in the current release to build towards that design. And yes, a good architect may admit that some of the design features he / she thought were required weren't actually needed. The difference between Agile and Upfront architecture is in when you find your 'Don't really need it' point. With Agile , you find it just before you build it. With upfront design / architecture you find it when it's already too late.



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3 Comments

Zhong Yang
2006-11-02 20:09:45
Agile is not engineering. Agile is art.
You can't expect an artist to do engineering work.
When you are doing Agile development you probable have a designer in the group, but I don't think you have an architect. Architect is a position in an engineering firm.
TConnolly
2006-11-06 16:18:48
I've been involved in 'agile' projects for the last six years. And developed for 16 years. My two cents, architecture matters not a jot, at least in the life cycle of a project. The devs will cope with things and keep the systems working and updating them. This is why outsourcing has been so successful. Cheap resources keep things running and get new features out cheaply. Crap code will run similar to an elegantly designed solution, thanks to excellent hardware. We, as developers, must get over the programming is art, the challenge is communication, programming is easy.
Robin Mulkers
2006-11-12 23:33:07
It seems that Design = Architecture for you.
I think these are different things.


Doing an Architecture is about caring about the feasibility of the whole system. The architect will design the backbone of the application by discovering less but essential requirements.


For example, is the application a Web Application or not? That's something that must be known at the beginning of the project, all the subsequent design activities will be influenced by this Architectural choice or requirement.
Another question, what framework will be used to build the application? etc etc


The Architecture phase of a project itself could be driven by agile techniques. But I think it is required to have it before the real development iterations.
The Design is about caring about all the use cases in all their details while Architecture is about having an overview of the system.
Robin