Monday, 30 April 2012

Reducing abstraction hunger

It's a bit of a pilgrimage, out here into the forest, and we have few visitors other than family. So those who do make it over the mountains are guaranteed a demonstration of Palimpsest if they show any interest. Yesterday's guest, old friend Michelle Greenwood, was the first hands-on user apart from me and Elizabeth. I couldn't have asked for a more sympathetic third user - as an engineer and musician, Michelle is about as similar to my own motivations as could be managed. So where I advise students to find trial users as different to themselves as possible for critical assessment of their interaction design, I have managed to avoid any critique beyond the blindingly obvious.

Nevertheless, there is clearly some work to be done, even in addressing the blindingly obvious. A first priority is to make a smoother transition between direct manipulation of shapes and geometric transformations of those shapes. At present, it is possible to rotate, translate or scale a shape either by dragging handles (as in a conventional direct manipulation drawing editor), or by specifying a geometric transform (which can then be adjusted by directly manipulating its parameters). However, the more powerful of the two - the transform layer - must be requested explicitly. Only after doing this can the user modify the transform under program control. Use of the direct manipulation handles is transient, changing the state of the object, but with no opportunity to reproduce or adjust that state change.

In CDs terms, this represents a combination of abstraction hunger and premature commitment. The user can either create abstractions routinely (thus allowing them to be adjusted at any time), or create them only when necessary - but this involves premature commitment to know in advance whether the abstract alternative will be necessary. Michelle was (unsurprisingly) unsure about the difference between the options, and confused by the implicit state changes between them. I can deal with this by, whenever a shape is directly manipulated, saving the state changes as potential parameters for a transformation layer, and giving the user the option to create that layer.

This does actually return to one of my first blog discussions - probably going back to last October. The was the point at which I created a "move" layer that was automatically generated in response to the user dragging of any content. This turned out to be rather annoying, as move layers quickly accumulated, appearing rather "heavyweight" for minor adjustments (a form of abstraction hunger, even though the abstractions were created automatically, in programming-by-example style). As a result, I created the direct manipulation handles in December. Now I understand that they should always have been combined, allowing transition from direct to abstract.

On the positive side, Michelle liked using Palimpsest, even in its prototype form. She said it was a lot of fun to play with, and immensely superior to her son's current experience as a student of introductory graphics programming, where it has taken him weeks of work to achieve the visual effects that she could explore within seconds. If I had any faith in Likert-scale evaluations of user experience, I could report an early confirmation sample!

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