Assume that your team was tasked with developing a large software system in any application domain of your choice. Also, assume that in order to manage the functional complexity of the system, your team iteratively applied the “separation of concerns” heuristic during the design process and settled on a cleanly layered system as such:
So, how are you gonna manifest your elegant paper design as a working system running on real, tangible hardware? Should you build it from the bottom up like you make a cake, one layer at a time?
Or, should you build it like you eat a cake, one slice at a time?
The problem with growing the system layer-by-layer is that you can end up developing functionality in a lower layer that may not ever be needed in the higher layers (an error of commission). You may also miss coding up some lower layer functionality that is indeed required by higher layers because you didn’t know it was needed during the upfront design phase (an error of omission). By employing the incremental slice-by-slice method, you’ll mitigate these commission/omission errors and you’ll have a partially working system at the end of each development step – instead of waiting until layers 1 and 2 are solid enough to start adding layer 3 domain functionality into the mix.
In the context of organizational growth, Russell Ackoff once stated something like: “it is better to grow horizontally than vertically“. Applying Russ’s wisdom to the growth of a large software system:
It’s better to grow a software system horizontally, one slice at a time, than vertically, one layer at a time.
The above quote is not some profound, original, BD00 quote. It’s been stated over and over again by multitudes of smart people over the years. BD00 just put his own spin on it.
Assume we have a valuable, revenue-critical software system in operation. The figure below shows one nice and tidy, powerpoint-worthy way to model the system; as a static, enumerated set of executables and libraries.
Given the model above, we can express the size of the system as:
Now, say we run a tool on the code base and it spits out a system size of 200K “somethings” (lines of code, function points, loops, branches, etc).
What does this 200K number of “somethings” absolutely tell us about the non-functional qualities of the system? It tells us absolutely nothing. All we know at the moment is that the system is operating and supporting the critical, revenue generating processes of our borg. Even relatively speaking, when we compare our 200K “somethings” system against a 100K “somethings” system, it still doesn’t tell us squat about the qualities of our system.
So, what’s missing here? One missing link is that our nice and tidy enumerations view and equation don’t tell us nuttin’ about what Russ Ackoff calls “the product of the interactions of the parts” (e.g Lib-to-Lib, Exe-Exe). To remedy the situation, let’s update our nice and tidy model with the part-to-part associations that enable our heap of individual parts to behave as a system:
Our updated model is still nice and tidy, but just not as nice and tidy as before. But wait! We are still missing something important. We’re missing a visual cue of our system’s interactions with “other” systems external to us; you know, “them”. The “them” we blame when something goes wrong during operation with the supra-system containing us and them.
Our updated model is once again still nice and tidy, but just not as nice and tidy as before. Next, let’s take a single snapshot of the flow of (red) “blood” in our system at a given point of time:
Finally, if we super-impose the astronomic number of all possible blood flow snapshots onto one diagram, we get:
D’oh! We’re not so nice and tidy anymore. Time for some heroic debugging on the bleeding mess. Is there a doctor in da house?
When I first encountered the work of each of these three original thinkers, it blew me away. Their insights on organizational and management behaviors were like a breath of fresh air compared to the C-suite pandering, jargonized junk that business schools spew and pop business icons like Tom Peters promulgate (no offense Tom, I like some of your ideas).
Managers who are skilled communicators may also be good at covering up real problems – Chris Argyris
AFAIK, there’s nobody like this trio of intellectual giants left standing (maybe they’ve won?). There are, however, a handful of second string, accessible, truth-tellers out there. Henry Mintzberg, Sam Culbert, and Steve Denning come to mind. Who can you add to this list?
In search of economies of scale, centrally planned and controlled economies in nations and corporations tend to create monopolistic providers of goods and services. For example, in corporations, accounting, personnel, and R&D departments are usually deliberately organized as subsidized monopolies. They are subsidized in the sense that the users of their products or services do not pay for them directly; the supplying units are supported financially by funds that are allocated to them from above. The pool from which these funds are drawn is filled by a “tax” allocated from above to the units served. Monopolistic units that are subsidized are generally insensitive and unresponsive to the users of their services, but they are sensitive and responsive to the desires of the higher-level units that subsidize them. These higher level units are even more removed from the units served than the serving units. As a result, they are often unaware of, or unresponsive to, the needs and desires of the internal users of monopolistically provided goods and services. – Russell Ackoff (Ackoff’s Best: His Classic Writings on Management)
OK, time to practice my “bent” UML modeling skills and test your understanding with the class and sequence diagram pair below. The class diagram provides a structural view of a fictional Ackoffian system. The sequence diagram steps through an amalgam of behaviors in a world where monopolies rule. Any questions, comments, critiques, accolades, WTFs?