The road to wisdom? – Well, it’s plain
and simple to express:
and err again
– Piet Hein, Danish inventor and poet.
When talking about CAD usability, it’s easy to focus on failings in the software. There are plenty of good bad examples out there that help prove the point. But, let’s be fair: even an ideal CAD program would be difficult for an average person to master.
That is because using CAD is a complex cognitive skill.
It can’t be made easy. Only easier.
To explain what I’m talking about, I’d like to start with a little cognitive science background:
Complex cognitive skills are goal-directed, and comprise a large set of interrelated constituent skills with different characteristics and different learning processes underlying their acquisition. In the context of CAD, those constituent skills range from simple drag-and-dropping to advanced surface modeling, to serious engineering problem solving.
The constituent skills that make up a complex cognitive skill have these charateristics:
- Some are performed as automatic processes, which primarily occur with little or no attention required, and others performed as controlled processes, which primarily require focused attention, and are easily overloaded and prone to errors.
- They may be classified as rule-based (recurrent skills), schema-based (non-recurrent skills), or, for complete novices, knowledge-based.
The process of learning constituent skills includes rule automation for recurrent skills, and schema acquisition for non-recurrent skills.
Rule automation is a concept that refers to learning processes that, with practice, allow a person to solve familiar aspects of problems with little or no conscious control. In the context of CAD, rule automation is important for constituent skills that must be performed accurately, quickly, and simultaneously to other constituent skills.
The term schema refers to a mental model or representation. Schema include cognitive maps (mental representations of familiar parts of one’s world), images, concept schema (categories of objects, events, or ideas with common properties), event scripts (schema about familiar sequences of events or activities) and mental models (clusters of relationships between objects or processes). In the context of CAD, schema acquisition is important for constituent skills related to unfamiliar or difficult problems, which require conscious thought and problem solving.
Most symbolic cognitive models of human information processing describe it in terms of data structures (representations), and the processes that operate on those representations. This is similar to the distinction in computer science between data and instructions. The term declarative knowledge refers to representations of objects and their relationships to other objects (e.g., the propositions we believe to be true.) It is “knowing what.” The term procedural knowledge refers to processes that operate on representations. It is “knowing how.”
How Does This Apply to CAD?
Automatic processes, controlled processes, recurrent skills, non-recurrent skills, rule automation, schema acquisition, declarative knowledge, procedural knowledge—you won’t find these terms discussed in the CAD for Dummies book. But they provide a foundation for discussing, and understanding, CAD usability.
Let me put them all into one paragraph:
When you sit down in front of your CAD system, you use a complex mixture of declarative knowledge (knowing what you want to do), and procedural knowledge (knowing how to do it.) You do recurrent processes automatically, without much thought, relying upon rote (rule automation). You do non-recurrent processes with control (conscious thought), sometimes solving problems you’ve never seen before by using your experience and domain knowledge (schemas).
A few days ago, I posted an article that discussed a broader definition of usability. While I went pretty metaphysical in my definition of usability (Usability is a measure of a tool’s ability capability to use what you have, to help you get what you want), I was trying to explain that usability isn’t just about user interface. It’s about your ability to get your work done.
But, let’s talk about user interface for a moment. How does user interface really affect usability?
Let’s try a thought exercise: Imagine you run a large aerospace company that designs and manufactures airliners. You have a choice between two different CAD systems: One with an exceedingly intuitive user interface (I’ll call this hypothetical CAD system “SpaceClaim”), and one with a modern, but arguably less intuitive, user interface (I’ll call this hypothetical CAD system “CATIA V6.”) Which CAD system is more usable?
Ignoring the false dichotomy in this scenario, you have to look at usability in the context of using what you have (a few thousand engineers and designers, among other things), to get what you want (high-quality airliners, delivered on schedule, on budget.)
Intuition in a user interface is primarily related to rule automation, and comes into play with recurrent processes that ought to be automatic (that is, you shouldn’t have to think too much about them.)
The not-so-hypothetical SpaceClaim, it can be argued, has a usability advantage in recurrent processes—including things such as navigation, and basic geometric modeling and editing. CATIA V6 has a usability advantage in many non-recurrent processes—including arcana such as knowledge-based engineering and aerospace surface design.
Most CAD industry analysts and pundits would argue that CATIA V6 is the more usable tool, when it comes to designing and manufacturing airlines. I’d tend to agree with them (however, if I were being ornery, I’d point out that a lot of aircraft flying today were designed with CATIA V4—a CAD program that is primitive compared to today’s best programs. They’d them point out that airplanes used to be designed on paper, and I’d point out that they had a point there.)
CAD Usability Doesn’t Really Suck
I admit—I went for the dramatic title in this series of articles. Maybe I should have called it “here are some reasons why CAD usability is a challenge.” That title wouldn’t have sounded as good on Twitter.
CAD usability is actually pretty good, compared to what it used to be. Yet, learning a complex cognitive skill such as CAD (and I’m talking about serious expert-level CAD, not just pretty-picture CAD) is inherently a lengthy process that requires high amounts of effort, and is constrained by human cognitive processing capacity.
Mastering CAD is never going to be easy, but there are a lot of things CAD developers can do to make it easier. I’ll talk about some of those in an upcoming post.
For further reading: Training Complex Cognitive Skills: A Four-Component Instructional Design, by Jeroen J.G. Van Merriënboer