« Desktop Zero | Main | Stress-Oriented Architecture »

With only a couple of weeks to go until SOA India 2007, I've been putting thoughts together for my keynote speech. Something I may or may not mention (haven't decided yet) is a comparison between "architecture" of the service-oriented kind, and "architecture" as practised by the cathedral-building stonemasons of the middle ages. Cathedrals were effectively the mediaeval equivalent of middleware - the large-scale infrastructure via which stakeholders in the Christian religion (i.e., church officials) serviced their customers (i.e., the Christian community).

Looking back so far, it is hard to know exactly what a master mason did when working on one of these huge buildings. However, we have some idea of the principles they used, and some idea also of the working practices employed by the guilds of the time. Interestingly with regard to a comparison with SOA, we also know that most of the work would effectively have been modification rather than construction from scratch. For a start, many of the major cathedrals were constructed over a period longer than a single working lifetime. Further, early cathedral building often proceeded on a trial-and-error basis - for example, there are records of buttresses being built only when certain parts of the structure started falling down.

This somewhat experimental approach changed in the gothic period, when new design principles meant that a small and elegant set of supports could hold up a huge edifice - and moreover, do so while letting in huge amounts of light. This transformed not only the construction process, but the experience of those inside the building - from being huddled in a cold and gloomy environment surrounded by yards of thick stone, to being bathed in golden rays of warming and uplifting sunshine.

So am I saying that SOA is like gothic architecture? A new and vibrant experience for the users, thanks to a step change in technological sophistication?

It may be, but that's not the point I'm trying to make. Rather, my point is about the difference between the two forms of architecture.

In general, cathedrals change their structure, very slowly, if at all. When they do change, it is usually by accretion - the addition of new buildings, rather than modification to the old ones. This means that the original design principles are largely unaffected by change. Hence, if a cathedral is still standing a few years after construction, it will probably still be standing a few hundred years after construction (barring the usual acts of god, or more often, acts of man).

With SOA, on the other hand, we can expect constant and often dramatic change both to the structure and functions of a system. After all, the main USP of SOA is that it helps facilitate such change! This means that original design principles are little or no guide to the longevity of the system. In other words, however clever the original designers were, the whole system can be compromised hopelessly by their successors at any time.

TAKE AWAY

A capacity to deal with change is often touted as the main attraction of an SOA approach. Yet this pre-supposes that change is managed properly. I see no evidence for this happening. Change on an enterprise scale, that spans multiple applications, is a complex human-driven process involving many different parties: usually many different departments, and often many different organizations altogether. The only tools SOA vendors are providing to deal with such processes are repositories for technical artefacts, that sometimes include the ability to make issue lists. In a nutshell, this isn't even close to enough, since it provides no mechanism for Human Interaction Management.

Further, the problem is exacerbated by subtle issues of system robustness - which we can glean from a deeper comparison between cathedrals and enterprise applications. Tune in to my next post for more mediaeval illumination :-)

Posted by keithhb in Service-Orientated Architecture |Digg This|Add to del.icio.us