How do UX roles intersect?

A while back I wanted to comment on Elton’s entry, Information Architecture updated to 3.0, and draw on a post to the IxDA list by Jay Fienberg, talking about the Venn diagrams that might show how the various user experience roles and practices tend to overlap. It seems that each type of practitioner has a tendency to see their own specialty as central and the other practices as peripheral. This isn’t limited to UX folks. You can encounter this with developers and visual designers as well.
One thing I really love about Extractable is the collaborative nature of the people here. No one seems to exhibit the sort of hubris that says “my practice is central – the rest of you need to follow my lead.” Instead there’s a true recognition that a fine user experience (based on a sensitive information architecture, incorporating engaging and immersive visual and interactive design, driven by a stable and responsive application) can only emerge from a process that enables a multidisciplinary team to collaborate as equals.
So, back to Jay’s point. He was responding to a list post by David Fiorito (itself in response to a thread following about the IA 3.0 blog entry by Peter Morville linked in Elton’s piece), in which David said, “Imagine a Venn diagram – one circle is IxD, one IA, and one ID,” as well as, “usability is the means by which we validate IA, IxD, and ID.”
Jay responded (and now I’m going to quote him in full because, well because I don’t think he’ll mind):

I’d add to that Venn diagram:

• content strategy / management
• visual design / graphic arts
• taxonomy

I’m thinking of a Venn diagram that represents possible approaches to dealing with “information challenges” (starting at a level or two up from requirements and objectives / needs*).
The areas of overlap in the diagram represent approaches shared by many or all of the disciplines. These common approaches tend to be sufficient for smaller challenges, e.g., there are zillions of web designers who design simple sites, and whose design encompasses IA, IxD, ID, and graphic art.
But, each discipline has special approaches that are unique to itself. These unique approaches are either important or essential for dealing with bigger information challenges.
I recently worked on a project that had at least one person doing each role of: IA, taxonomy, IxD, visual design, and usability. We also could have used a dedicated content strategist and a dedicated content manager. And, some time from a dedicated ID would have been nice too. We needed each person to do things that the others could not do – or, would not ever get to do, given the range and priority of issues.
* Jesse James Garrett’s “The Elements of User Experience” diagram still stands as a pretty good model for of all of this stuff. We might imagine this Venn diagram we’re talking about as a flattened version of Jesse’s diagram. Note that Jesse is probably smarter than all of us for looking at this in two dimensions rather than one – the IA / IxD dichotomy seems like a very minor division in the total scope of factors accounted for in Jesse diagram!

I’ll follow up by noting that Morville has his own honeycomb diagram that places findability in among usability, accessibility and other -bilities. Another famous IA Peter, Peter Boersma, has also popularized the concept of T-shaped people to help explain the sort of well rounded people who often end up architecting information, designing interactions, making interfaces easier to use and so on. They may tend to have a specialty (the “leg” of the T) but they are also broad and have some familiarity with and interest in a series of other “pillar” disciplines (the crossbar of the T – it’s easier to visualize with Peter’s diagrams).
I expect to see these conceptual discussions continue, perhaps at one degree of abstraction (we are all diagram people after all), where instead of practices competing for centrality we’ll see models of how the practices relate to each other competing for supremacy. Good times.