[Continuing the discussion of the PM Job And Department Profiler from the previous post.]
The most fundamental decision for the Profiler was the choice of how to depict the PM role. I might have chosen functional areas, such as Pragmatic Marketing's famous diagram of PM responsibilities, or something skill-based, such as Steve Haine's efforts to define product management and product marketing as a corpus of knowledge that people in that profession need to master. Instead, I decided to use tasks to build the picture of what PMs do.
There's nothing inherently wrong in the other depictions of product management, but they weren't the right raw materials for what I wanted to do. If I accomplished nothing else, I wanted to depict the volume of work that PMs do, and the degree to which that work is focused or unfocused.
The Pragmatic Marketing periodic chart of responsibilities tells you how to categorize the work, but the categories don't point directly to the amount of work. A skill-based approach tells you how many different skills you need to acquire, and might even suggest how challenging some of those skills are to learn. However, that doesn't tell you, in hurly-burly of daily work, how much time the tasks that require those skills will take, or (again) how challenging it is to juggle competing priorities.
From zoology to ecology
The closest analogy I can think of is biology. As my graduate adviser said, "Every science begins with classification." That's what the Pragmatic Marketing framework does very well: define the different species of responsibilities that constitute the family tree of product management and product marketing. However useful and necessary classification may be, it doesn't answer all the questions of biology, such as, "Why do these species dominate, and these other ones don't?"
To take this analogy further, job descriptions are like ecological niches. Many different species might fill each niche; not everyone is equally well suited to do so. (By the way, the number of niches keeps expanding, but that's a topic for another post.)
Tasks, therefore, are the essential traits that determine the success of a PM in each niche. If the PM is doing the wrong activities, or is too busy to perform the essential activities, then that PM won't do well within that niche.
The ecology of vital business activities
Classification tells us what species have evolved to fill these niches. Skills, like DNA, define what the species is capable of doing. However, if the question at hand is, What kind of PM should we have? the answer depends on what the PM is actually doing within a particular niche, a.k.a. job category.
Or, to look at it another way, classification of PM job categories is interesting, but it's not a very convincing argument for why a company should adopt one species over another. On the other hand, discussions of skills is sometimes premature, because it begs the question, What's the vital business function for which these skills are necessary? Tasks, as it turned out, were a better starting point for defining the vital business functions in a way that might lead to a fruitful discussion of, We need this many PMs in these specializations to do the job right.