Expressivity
Caveats
Most if not all pages are just rough notes, and these pages as a whole are far from complete. More notes will be added in time, eventually, maybe.
If, from reading these notes, you conclude that I am off my rocker, you won’t be the first, and you may even be right.
No doubt there are a dozen and one reasons why none of this would ever work, but perhaps somewhere deep down there is a tiny fragment that could be used for something.
“Expressivity” is a makeshift word representing the concept of the extent to which one may express an idea to computer such that it can be understood and obeyed. Humans are gifted with comprehensive natural language, while computer user interfaces offer only the equivalent of a minuscule syntax and vocabulary. For any given UI context there will be many notions that the computer cannot be made to understood; these can be single actions (e.g. delete a file) or compound tasks (place all JPEG images in a particular folder into a zip file named with today’s date).
As a clear example, imagine that you have created a blank playlist in your music player and added all the MP3 files from a specific folder into the playlist. Now imagine that you want to save the playlist file back into the same folder. At this stage, your desktop will look something like this:
In Microsoft Windows, there is no conceivable way to express directly to the computer that you wish for the new file to be saved into the window directly to its left. The user is, for example, expected to navigate within the Save As window all the way around to the folder that is right there staring it in the face. This is an expressivity void: a trivial concept for which there is no means to express the request to the computer.
Such voids often reflect a lack of innovation. A simple solution would be for Save As dialog boxes to have a widget for choosing any open folder window as the target. This would make life much easier when adding material to a folder from multiple applications.
RISC OS actually made this concept directly expressable. When saving a file, the full path must be supplied, rather than simply the name. However, the intention was that you would use drag and drop to “move” the document into its target location:
The gap between what an end user has in mind and the ease with which they can express this intention to the computer affects the system’s overall usability. As such, user interfaces need to be as discoverable as possible, so that users can readily avail themselves of the interface features on offer.
Note that the RISC OS approach is not universally suitable. It requires the user to be able to operate a pointing device effectively (not a given) and for the display to have capacity to fit both windows side-by-side. The example above used windows that were deliberately reduced in size, but on the Acorn Archimedes’ default screen resolution of 640×256 pixels, being able to see both windows at once could be a challenge, especially with its poor window management capabilities.