A constant found among the many definitions of IT architecture is rules. In whatever way you do IT architecture there will always be a moment where you say: "This design does not conform to the IT architecture, please revise". This approach is now proliferated through organisations by means of enterprise architecture, no longer only IT systems and their designs are obliged to conform to certain sets of rules but now complete organisations are. I don't believe in rules for their own sake. This calls for a closer investigation of the phenomenon "rule". As a first step I want to propose a distinction between two types of rules: arbitrary and material rules.

Arbitrary rules are rules that are arbitrary, you could equally well have chosen for another rule (within some domain of choice say). Keeping right in traffic can serve as a good example. We could have chosen to keep left without any problem, as long as everybody makes that same choice. In this case the domain mentioned consists of two possibilities: right and left. The idea behind the concept of arbitrary rule is that you have to make a choice (maybe "choice rule" is a better name) for otherwise chaos will reign and any choice is valid as long as everybody adheres to the same choice.

Material rules are rules that have a materially contingent impact. You can go on holiday to either Gran Canaria or Kabul (or not at all), now it does matter what you choose for the impact of each decision is radically different. Organisations are constructed using many of these material rules. They have chosen to be an A-brand or challenge the market with product leadership, and they have chosen to do so by outsourcing all non core activities and to split the company according to mutually exclusive market segments.

Now rules in general have an interesting property: they are like the skeleton of a human body. The skeleton gives stiffness to the body which is why it can become so large and functional. The other side of this necessary stiffness is rigidity, there are many instances in which you would wish your body more flexible but alas it is not. In the same way organisations both enjoy and suffer from the rules that make up the organisation.

The interaction of arbitrary rules to this property is different from that of material rules. The key to understanding this is in levels of conciousness. The level of conciousness at which an arbitrary rule is created (nearly) coincides with the level of conciousness at which that arbitrary rule is executed: the only reason for keeping right is to prevent collisions. But the level of conciousness at which a metarial rule is created usually does not coincide with the level of conciousness at which that material rule is executed: the reason for chosing to be an A-brand might be because there is still room for an A-brand in the market place (or because it suits the CEO's identity better for that matter).

What happens too often in organisations is that choices made, sometimes far away in time or distance, are understood at the the level of conciousness at which they are executed instead of at the level of conciousness at which they were created. This effectively means that these rules are not really understood at all. This means that by implementing (too many) material rules employees stand the risk of operating at a subconcious level. This drawback seriously threatens the appropriateness of (material) rules and so of enterprise architecture.