Tuesday, 10 November 2015

You Cannot Iterate upon Architecture

This is the first part of a series of posts as to why gradual iteration, doing the simplest thing that can possibly work over a software project fails in many cases. This series will explain why this is the case, and provide solutions.


Spotify has gave a talk on how it builds products and manages teams internally. This provides some great insights and advice. As part of this an incredibly effective image is used. This shows the production of a form of transport to travel from A to B.

In the first half of the image, the product is built in iterations. Each step adds to the next. It is not until the fourth step that the product is able to take passengers from A to B. Agile development aims to solves the issues around this.

The second half of the image is built iteratively. The goal is still the same. A product to travel from A to B. From the first version this goal is complete. However the team would be embarrassed to release in this state. Further iterations are carried out as the team learns more.

From my experience building software in this manner only works half of the time. Any software projects from my first line of code up until present day fall into one of two categories.

Known Projects or Unknown Projects

A known project would be where the destination is clear and well defined. Internal development projects, refactoring, or replacement would fall into this category. Easily half of my professional time has been spent on projects where we know what we are building and when it must be complete by.

The second type of projects is where the destination is unknown. You are working for an external customer directly. On a regular basis you regroup with the client. You gather feedback and iterate. Over the course of this process your destination may very well surprise you, along with the route you use to get there.

Refactoring is Class or Method Level Only

You could claim the image works for unknown projects. At any point the client (internal or external) could put a halt on development after their vision is complete. For known projects, the area this image fails is simple - if a car is required, build a car. If this is demonstrating a known project, building only then to start recycling, refactoring and forming the code into another shape is costly. Sticking with the vehicle analogy - building a car is complex. In one iteration it would not be possible to gather feedback until it was too late. Much time and resources would be wasted.

Translating to a software example, this would be the same as building a complex web application. The goal is known, yet the first stab is a HTML page. This is followed by some simple sever side logic. On top of this we add an ORM. Further iterations thrash and push the code around. Early simple decisions start to come back to haunt us. This technical debt is either repaid or ignored. As further iterations follow the architecture of the application suffers. Through sheer force of determination the web application is complete. Usually there are many compromises along the way. Further enhancements or changes could be costly.

Solutions

For unknown projects there are two solutions. First and foremost build a walking skeleton. Using the vehicle example, the first iteration of a known project should produce the frame of the car. Other than wheels there would be very little else here. However this is still a car, though limited in functionality and features. Using the software example this would be the core flow of the web app. Either hardcoded in places or built using scaffolding. You would still be embarrassed to release this. Architecturally you have all the core parts you need. The benefit of this is that future iterations simply build upon the good, known framework. The foundations of the project are stable. There is no fear that after several iterations you stumble upon a technical implementation issue.

The second solution is turn an unknown project into a known project. This sounds difficult but there is a remarkable easy way to achieve this - the subject of the next post.

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