Monday, July 23, 2012

Making your architecture scream!

[Note: This is a repost of an entry I wrote for my company blog at]

I've mentioned before that I'm a big fan of Robert "Uncle Bob" Martin. One of his latest projects is the Clean Coders "Code Cast" that I've been watching with some Intunity+Client colleagues on a client site. Uncle Bob does have his quirky moments; but it's great to see the discussions that the material brings about within the team I'm working in.

The latest episode on architecture made me think of another project that I worked on where the project was so tightly coupled to the DB that it made it impossible to reuse the domain model (a mate of mine had a similar problem that I've written about before). This hampered development and lead to some ugly code.

UB's point in the episode was that the architecture should scream at you what it does. His example was of a Payroll system that should scream "accounting software" at the coders; not the technologies (eg: web, database, etc) used. Following on from that idea, my thoughts turned to the practise of Domain Driven Design where we want to place as much logic (or behaviour) into the domain model. After all it's the place of the Dog class to tell us how it speaks(). So that means you should develop your domain model first (that which screams at readers what the initial design is) and bolt on other features to meet requirements (with those requirements preferably defined with User Stories in my opinion). The core of the architecture is the model, but with the ability to evolve the model and the other features of the application. This is great for the business because it can get more features released! The model can be exposed/manipulated in a SOA by moving representations of the model (resource) around (ala REST) - or not. Developers haven't been bound to a particular technology which hampers their ability to write useful code for the business.

However there are some business decisions made that can cripple the ability of a team to achieve this outcome; where the architecture consequentially whimpers. Usually that revolves around the purchasing decisions made by the business. In UB's episode the DB was a "bolt on" to the architecture. The DB was used to store information that was given "life" in the domain model. It can be added at the last responsible moment to reduce risk to the business that their purchase will be in vain. The focus of the application was in the model, not the DB product. So what happens to your architecture (and all the benefits of a rich domain model) if your business engages a vendor to consult on your business' architecture who's business model is selling a product (or licenses for a product)?

Like UB, I like to see an architecture that screams at me what it's doing - that way I know that it's benefiting our clients, and that I can punch out feature, after feature, after feature.

No comments:

Post a Comment