More complex magic procedures

[geoff-h -at- MTL -dot- FERIC -dot- CA]

 Michael Wing keeps right on upping the ante on the problem
 of providing context: <<Flowcharts, cartoons, decision
 trees, and so forth aid in learning the sequence of what to
 choose and in which order to choose them but still
 does not satisfy the need for the user to understand the
 ramifications of combining choices.>>

 This is getting progressively more interesting... and no,
 I'm not being facetious. Mike, you're posing us an
 increasingly complex problem in information design, and I'd
 be surprised if we can't crack it for you with a few more
 details. Let's keep going on this!

 <<If two parameters each have ten settings, there are a
 hundred possible outputs.  Now, illustrate the outputs for
 10 parameters with a selection of settings ranging from 2
 to 25.>>

 You can undoubtedly simplify the problem considerably if
 you define things in terms of user tasks rather than simply
 permuting all the possible parameters. I doubt, for
 example, that users will pick a line width and then fart
 around with scales and azimuths until the find one that
 works with that line width. Typically, users will want to
 fit a map on a given paper size, with legible lines, at a
 predefined scale (e.g., the 1:10 000 airphoto standard in
 Ontario).

 For example, pick the main parameter that characterizes a
 specific task, and try a restricted example to see whether
 it leads us to a general principle. [Caveat: I'm not
 proposing a final solution here, and I haven't double
 checked my logic/math/etc. It's just an example.] Let's say
 the user's task is to produce a map that fits the Ontario
 scale (a specific example of the general task of producing
 a map with a specific scale). You might get away with
 something like this:

 ***Map scale***
 Once you've defined the area that will be included in
 your map, setting the map's scale determines the size of
 the final printout, the size of the features visible on
 that printout, and the amount of RAM required to process
 the image.

 Printout size: For a given area, increasing the scale
 increases the size of the printout; for example, doubling
 the scale doubles the printout size. To avoid having to
 tile your output, we recommend using a pin-fed plotter.

 Size of map features: If you reduce the image size, you'll
 need to increase the thickness of the lines to compensate.
 Conversely, if you increase the image size, you'll need to
 decrease the thickness of the lines so they don't become
 unacceptably thick.

 Memory allocation: The status line displays the size of the
 printout based on the scale and area you've chosen. The
 larger the printout, the more memory you'll need to handle
 the map. We recommend 1 Megabyte of RAM per square inch.

 And so on. The text and the example are admittedly trivial,
 but the essential point isn't: Start with the task, and
 identify the implications of each parameter/setting for that
 task. If you understand what your users will do with the
 software, you can prioritize the main settings or recommend
 a sequence of settings. In the previous example, the
 sequence would be define your area, pick a scale, and adjust
 the output parameters to match. Continue from there!

 <<Often, these types of applications use successive
 approximations in which the user gets within range of the
 expected results on the first iteration and then tweaks
 the input parameters to reach the goal.>>

 Well, the above approach provides much of that theory
 indirectly, but it's not possible for anyone other than a
 chess master to keep all those possible permutations in
 their head. Your goal should instead be to give enough
 theory so that users can quickly reach the stage where all
 they're doing is tweaking a single parameter. The
 recommended sequence of activities will vary for each task,
 as will the parameters you need to define closely. This sort
 of problem is beginning to intrude on UI design more than
 documentation, and seems tailor made for the sort of
 approach that some photo editing software uses: provide a
 palette of thumbnail images and let the user pick the one
 nearest to where he wants to go.

 --Geoff Hart     @8^{)}     geoff-h -at- mtl -dot- feric -dot- ca
 Disclaimer: Speaking for myself, not FERIC.