Separation of concerns — What is that for?2016-11-03T14:05:08.876Z

Embracing SoC* over DRY*

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&TLTR; The post contains a lot of theories and abstracts. Sorry, no code this time.

Separation of concerns [SoC] , Keep It Simple and stupid [KISS],Don’t repeat yourself [DRY] are typical examples for principles in software development.

Why do you need principles?

Principles are some kind of distilled source of truth that come from experiences. They are internally motivating and guiding you to do the things that seem good and right.

Principles are good for your code.

In this post I would like to focus on Separation of Concerns that helps me the most dealing with the challenges in a complex, resistent corporate environment.

Separation of concerns — Divide your application into distinct features with as little overlap in functionality as possible. The important factor is minimisation of interaction points to achieve high cohesion and low coupling — Microsoft

You can read more about the the basics at wikipedia , effectivesoftwaredesign or Microsoft .

Silos and monoliths

Misinterpretation and unbalanced use of principles result in bad architecture, witch-hunt after duplications and unnecessary bureaucracy with hand-over process madness. It could happen on every level from code to enterprise architecture and always ends in one of the following results:

  1. The crazy optimisation breaks down the boundaries between components and ends in a monolith.
  2. The extreme level of centralization combined with mindless separation of building blocks creates organizational and technological silos.

This Is insane.

Finding and keeping the right balance is art. That doesn’t mean it is impossible. In short: use them wisely.

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Separation of Concerns

In the following I would like to focus on Separation of Concerns and how this principle encourages and strengthens collaboration. Yes, you have read it right — I would like to talk about collaboration in the context of separation.

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When you are separating, isolating or decoupling things , there is always a point where you realise that the components you are working on are part of a bigger context. They are not islands. Their purpose is to be part of something bigger. That requires collaboration.

I would like to turn your attention to that thin layer between the components, the boundary that is establishing the separation. Focus on that and forget about the rest for a moment.

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Every time you are writing code, defining software architecture or describing requirements I suggest to start working with theses boundaries. Identify your external dependencies and define the communication channels between you and the rest of your world.

Define your API First!

Than fill up the components with content. The following benefits come with this approach:

  • Natural way of reducing complexity by giving access to the larger context.
  • Experimenting is cheap with an API.
  • It brings an easy common understanding of the problem that needs to be solved.
  • By design it creates a clear cut between your components, and at the same time establishes the contract for future communication.
  • It is encouraging discussion between the parties (teams). Each of them can focus on their own side of the API.
  • Mocking and stubbing will be a straightforward activity that ease testing.
  • API is transparency.

The word API [Application Programming Interface] is related to software development but I would like to encourage you using this technique on higher level as well, or in different contexts, even in organisational development.

Let’s take a look at a few example.

The most basic API you can find are the function definitions laying in your code. In Object Oriented Programming defining Interfaces could be the API. Of course REST APIs or Web Services are de facto APIs. SLAs in the context of an IaaS are the API facing the users., are the API’s of a Self-contained application thet helps driving through the stages of the lifecycle. They establishing contact with the different systems responsible Build — Test — Deploy.

A Cross-functional team using kanban has an API including their backlog and their kanban-board. Definition of Ready [DoR], Definition of Done [DoD] are the API for delivering etc.

Finally I hope you have enjoyed this short tour into the abstract world of software architecture and at least a few af these thoughts help you the next time when you have to deal with boundaries and collaboration.

External resources in the topic