ACCU2016: Talk on Software Architecture Design 6: Organising Principles

I now want to try and explain the idea of an Organising Principle more clearly.

As an introduction they have a number of characteristics. They:

  • Embody a Living Wholeness.
  • Have a high degree of Ambiguity.
  • Are never Static.
  • Lie Behind the Parts.

ElanWoods

Embedded within a set of requirements is something that we need to find and embody in our implementation. As with high level schematics, there is a high degree of ambiguity surrounding this ‘something’.

During the talk we have moved from the high level schematics where I can hand wave to my hearts content about structure and architecture; down to diving into the depths of the actual implementation.

You may remember Andrei Alexandrescu’s keynote where he was talking about the details of a sort algorithm – first thing in the morning. Difficult after a late night before!

When trying to understand what he was talking about we are need to think at multiple levels:

  • Listen to the words he was saying.
  • Read through the code examples in his slides.
  • Imagine the dynamic behaviour of these code extracts.

In order to comprehend how this algorithm works dynamically, the listener needs to use their imagination at the same time as trying to understand what Andrei is saying. During this particular talk you could palpably feel the intense concentration in the whole audience.

During deep technical discussions listeners will work at these two levels of understanding:

  • The static code structure.
  • The dynamic behaviour of the static construct.

In addition one will only be looking at a single possible instantiation of a solution. There could be alternative ways of doing the same thing.

The term I like to use here is that during this process we are trying to ‘Livingly Think’ the Organising Principle.

An Organising Principle is NOT a static thing. It cannot be written down on a piece of paper. Although it informs the implementation it cannot be put into the code. If you fix it: You Haven’t Got It. Remember that phrase because getting it is the real challenge. It lives behind the parts of any concrete implementation.

I am explicitly using this separation of Whole and Parts, a discipline called Mereology. How can we understand the world in terms of wholeness and yet also see how the parts work therein?

Experienced people will have a sense of the whole and yet will be able to see where the likely risk points are going to be. They simultaneously see the whole picture and also know the essence of what needs to happen in the parts. This is what you pay for when you employ an expert. In my design example, for instance, an expert will know to ask about your allocation strategies and if they see some allocations going out of order they will point you at where you need to change the system.

Requirements implicitly contain Organising Principles.

They implicitly, not explicitly, embody dynamic specifications of what needs to happen. Much of my job when I talk to any customer is to try and understand:

  • What they want to do.
  • What I think can be built
  • How I can bring those together.

I need to understand what the core dynamic principles are that are embedded in their requirements. By definition if you are doing a useful piece of software the customer wont know what they actually NEED. They can talk about what they WANT, but that is based in their present experience. The conversation between the user and the developer will be generating new knowledge about future experience.

[Software development involves moving knowledge from the Complex to the Complicated domain as Cynefin defines it. This means we are dealing with emergent knowledge.]

Architecture references the Organising Principle.

If we take the point that an Organising Principle is not a fixed, discrete idea then we can see that it is much like comparing a film of an activity with its reality. The film is just a set of discrete frames, but the reality is continuous.

With software, the different architectures and implementations are different views of a specific Organising Principle. This is very hard to get our heads around and needs a far more mobile thinking than we normally use. This is the core of why good software development is so difficult.

Code is the precipitate of the Organising Principle.

If we manage to perceive this dynamic principle, referencing it by designing a software architecture that we embody into a specific code implementation, we are embarking on a process of precipitation. If we DON’T do this then – indeed – we only have a “Hopeful Arrangement of Bytes” as this talk title suggests.

Of course this may be a valid thing to do sometimes as a piece of ‘software research’ just to see how the code works out. This is especially relevant if there is a blank sheet, or ‘green field’ site where you just have to start somewhere. In this case you need to look at the part of the requirements that represent the riskiest aspects and just implement some proof of concept solution to check your understanding.

This is where it may not be an idea for a novice or journeyman programmer to follow the example of an experienced one.

Be warned: It is possible that a master programmer may be able to work at the keyboard and seemingly design as they go creating from internalized mature ideas. This is something that is definitely NOT recommended for inexperienced developers who will need to spend much more time maturing and externalizing their ideas first before those ideas become part of their ‘cognitive muscle memory’.

In the next and final post of the transcript of this talk I will deal with how to improve our perception of Organising Principles…

ACCU2016: Talk on Software Architecture Design 7: Perceiving Organising Principles
ACCU2016: Talk on Software Architecture Design 5: Active Design Ideas

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