Wednesday, February 08, 2012

WIGGLE Charts—A Sketching Tool for Designers (Part 2)

Wiggle Charts (Part 2)

Perhaps the nicest feature of WIGGLE charts is the way they can be used with just about anybody's diagrammatic technique.

The following figure shows a Hierarchic WIGGLE, or a WIGGLE Visual Table of Contents (WVTOC) for use with a HIPO system. In this application of the WIGGLE, the overall size of the boxes can be used to indicate (roughly) how big an effort we anticipate in building this box. Alternatively, it can be used to approximate how much execution time or other resource we expect to be consumed here.

A WIGGLE visual table of contents from a HIPO system (Each box has input on left end, output on right.)

The next figure shows a Nassi-Shneiderman WIGGLE. In this chart, the size of the wiggles in the diagram indicates roughly how uncertain we are of the particular part of the design. 

A Nassi-Shneiderman WIGGLE
The vertical loop wiggle is quite small, perhaps indicating we're not sure if the loop is to be done N or N+1 times. Similarly, the slanted wiggles on the decision are small, indicating perhaps we don't yet know just where the "equal" case will go. But the large wiggles dividing the right branch of the decision into three boxes are very large, indicating great uncertainty about the functions to be performed here.

All these conventions may be applied to sides of boxes, regardless of the shape of the box, as well as to arrows or other lines connecting boxes. Each of these charts should be sufficiently "clear"—as sketches—to readers who can read the original, unwiggled, chart.

Just for completeness, the next figure shows a key to the use of the WIGGLE. Using this figure, you should be able to begin sketching your favorite design pictures using the WIGGLE, even if you're still in love with good old flowcharts.

The WIGGLE system condensed to a few simple rules applicable to any graphic scheme

This material is adapted from my book, Rethinking Systems Analysis and Design.

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