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Systems Engineering Architectonics


No, not really a photograph of me - say, you guessed that didn't you! I like Yoda, that's all. Mind you, I'm not sure what he is staring at...

So, what is Systems†Architectonics?†It describes a subject which barely seems to exist - the study of systems architecture. It seems that we presently lack the ability to examine a situation and then prescribe a systems architecture best suited to that situation.

Contents

  • The Missing Science
  • Aspiring Architectures
  • Animal Architectures
  • Architecture's Mission
  • Kinds of Architecture
  • Layered Architecture
  • Layered Architecture and Mathematics
  • Clustered Architecture

The Missing Science

The problem is presented in the following picture, which shows the so-called Missing Science, and suggests sources that might contribute to it:-

  • Architectural archetypes
  • A mathematics of architecture
  • Architectural metaphors, and...
  • Learning from past and present architectures

That's the plan - but can we do it without falling into traps such as:-

  • reinventing the wheel
  • making false deductions because the environment that spawned some old architecture is no longer relevant
  • misreading metaphors
  • etc.

Aspiring Architecture

At left is Salisbury Cathedral, centre is the Seattle Expo tower and right is the Forte Grand, Abu Dhabi

  • The buildings nations produce exhibit features consistent with their national development and contemporary psyche, indicating confidence, severity, retrenchment, exuberance...
  • Young, confident societies/civilizations create monuments to their future, reaching to the sky. Buildings tend to be massive, but with purity and severity of line, e.g. pyramids, cathedral spires, Eiffel tower...
  • Wealth creates architectural variety. Impoverishment results in architectural monotony
  • Poor/demoralized societies do not build monuments to a future in which they have no confidence. Nor do they invest in infrastructure to connect and bind their societies together. Through the ages, and today, architecture is a barometer of societal psyche

Animal Architectures

The figure shows several different animal architectures - see Cambridge Encyclopedia of Life Sciences. As the architecture becomes more complex, both advantages and problems arise:-

  • animals become better able to accommodate different environments, process different resources, remain viable between meals, etc.
  • energy distribution and waste collection, instead of simply occuring through a cell wall, require canals, arteries, etc.
  • heat generated in the centre is less well able to escape
  • etc.

It soon becomes evident that, as architectures become more complex, waste disposal becomes a significant issue.

Scaling of architectures becomes problematical, too. While the surface of exoskeletons increases with the square of their radius, the volume (and weight) contained increases as the cube of the radius. Result? Beyond an uncertain size limit, exoskeletons are ineffective.

Humans have developed a composite skeleton. While most of our skeleton is internal (endoskeletal), our brains are protected by our skulls, effectively an exoskelton. Similarly, our rib cage protects our lungs and softer organs within. Here, the rib cage is an incomplete exoskeleton to reduce weight and increase flexibility.

With a little thought, it can be seen that these "rules" through which animal architectures have evolved can be more generally applied:-

  • Waste management is crucial
  • Architectures do not scale


Architecture's Mission

  • Architecture expresses purpose in man-made systems - architecture is the structural framework giving form and substance to a system, but architecture is more - by its very form it expresses viewpoints, contains information, affords adaptability to new purpose, marks territory...
  • Examining the architecture of evolved buildings suggests a set of attributes which could be expected of successful architecture for any kind of modern system
  • Using Interpretive Structural Modelling, these various objectives can be formed into an objectives "tree" or Attribute Enhancement Structure

Kinds of Architecture

  • Appears in many forms, with decoration sometimes concealing much underlying structure
  • Structure offers two main archetypes:-
    • Layered architectures, enabling or resisting passage through a structure comprised of successive layers, perhaps undergoing transformations, and finally exiting. This is the basis of process oriented architectures used in manufacturing, communications, defence and security, trees and plants, the Sun, alimentry canal...
    • Clustered architectures, where architectural components form into groups, perhaps with a view to reducing energy of, or time taken for, interaction between the components. This is the basis for architectures used in human organization, circuit board and microcircuit design, some evolved biological “designs”, topics in textbooks, parts stored a warehouses, ethnic restaurants, books in a library...
  • In many systems, layers form as a result of clustering


Layered Architecture

Method used since pre-history is the layered defence:-

  • Instead of a single, eggs-in-one-basket, barrier, several barriers in succession
  • Each layer need not be perfect
  • No single barrier responsible for all “neutralization”
  • Attackers/intruders faced with time-consuming series of hurdles
  • intruders exposed to detection/attack for longer, presenting greater threat of detection
  • intruders must carry variety of tools/weapons/etc., to tackle each (different?) layer of defence
  • Bona fide entrants less inconvenienced
  • in multi-layered system, each layer need not be so demanding

  • The figure shows a typical high security area, with fences, sanitized zones, automatic cameras, even weapons (unusual in most countries, but not unknown worldwide.)
  • There are some ten layers - note that a sanitized zone is a layer, as well as a fence.

Layered Architecture and Mathematics

The simple equation adresses the probability of passing through a series of N layers one after the other, each having the same probability of neutralizing, i.e. of preventing further passage.

The equation produces the following graph:-

Looking at the graph, it soon becomes clear that the lines for succesive layers are getting closer together. Evidently, there is some law of diminishing returns at work.

  • If you have one layer, then a second gives a great benefit.
  • If you have 6 layers, then an extra layer confers much less additional benefit.


The cost, in terms of effort, in adding each additional layer, may soon prove prohibitive. Consider Maiden Castle:-

  • Counting earth ramparts, Maiden Castle had 5 layers of defence
  • Counting ditches between ramparts too, there were 11/12
  • Note at left and right ends, the additional earthworks guarding the entrances - always a weak point


To a first approximation, the circumference of each ring goes up as the square of its radius, so each successive ring going outwards from the centre must take significantly longer and cost more.
Add to that the diminishing return for each new ring, and it soon becomes evident that there was a strong pressure to have the "right" number of rings, where right means that the rings provided effective defence at an affordable cost.


Clustered Architectures

  • Systems architecture can be thought of as the organization and grouping of things for some purpose. Architecture, then, is servant to some higher purpose
  • Systems engineering architecture tends to afford the foundations of performance, rather than aesthetics
  • Often, exchange of energy, substance or information between parts within a system easier/uses less energy/faster, if distance between parts is shorter.
  • Moving two parts closer to each other to improve exchange extends other links - hence some optimum arrangement improves overall performance
  • That is†systems†architecture design - finding the optimum for whole system, not just some parts

  • In going from the upper to lower diagrams, a degree of order has been introduced - or, if you prefer, entropy (the measure of†disorder) has been reduced.
  • The entropy reduction is real. In the two figures, the sum of all the link-lengths joining the entities is greatly reduced in going from first to second figure. This shortening equates to untangling, hence to real entropy reduction.


For clustering, consider:-

  • The value derived from clustering depends on the nature of the system whose parts are clustered.
  • Where there is advantage to the overall system from reduced time or energy utilization in the interchanges between internal parts through internal infrastructure, then advantage may accrue from reduced overall link-length. This condition pertains for many systems but not for all
  • Advantage may also accrue from proximity between some parts of one system and interacting parts of another system. In such cases there may be a trade-off between internal advantage and overall advantage
  • e.g. Analysis of aircraft under ground control shows that control reliability would improve if aircraft and controller were co-located. This is impractical. Hence an alternative strategy emerges— the provision of high-integrity, redundant communication channels between aircraft and controller

From the N2 chart, note the following:-

  • There are two functionally bound blocks, one for airspace control and one for ground movement control
  • There are three connected control centres.
  • The approach and takeoff control is at the centre of a "cross" of interfaces, showing it to be a vital node - if it were not there, the system would separate into pieces
  • All parts are connected, but only via one of the three controls


Last updated: Feb 2005

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© D K Hitchins 2017