An onion (or onion skin) diagram uses concentric circles to represent layered systems. Each component is a ring that builds on a single, core component, as Figure 11-5 shows. All the shapes you need to create an onion diagram are located on the Blocks stencil, which opens with the Block Diagram template.
To create an onion diagram, start with the outer concept and work your way in. Use a concentric layer shape of the appropriate size to represent each new concept or layer. The concentric layer shapes fit together tightly. As long as you have no more than four layers in your diagram and don’t need to resize shapes, the diagram is easy to create. To represent five or more layers, you must manually resize the largest concentric layer shape to fit.
Follow these steps to create an onion diagram:
Perhaps the biggest challenge when working with layer shapes is getting the text to fit. Visio 2007 doesn’t support text on a curve, so long lines of text can extend beyond a layer’s borders. To enlarge a layer so that more text fits, drag a corner selection handle, as Figure 11-6 shows. You can enlarge each layer in the onion diagram a similar amount and then realign the shapes or select all the shapes (either lasso them or hold the Ctrl key while selecting each) and enlarge them simultaneously. Other techniques for revising shapes are summarized in Table 11-4.
Task | Technique |
---|---|
Align onion layers | Select all the layer shapes, and then choose Shape, Align Shapes. Choose a horizontal and vertical alignment option, and then click OK. |
Change the thickness of a concentric layer | Drag the control handle on the shape’s inside rim to the thickness you want. If you don’t know which control handle to use, pause the pointer over a control handle to display a ScreenTip. |
Move the text label on a layer | Drag the control handle in the middle of the label. If you have trouble dragging the handle, disable snapping—Choose Tools, Snap & Glue, clear the Snap check box, and then click OK. |
Although onion diagrams are not complex, you can represent complex ideas by segmenting a layer. The partial layer shapes (Partial Layer 1, Partial Layer 2, and so on) on the Blocks stencil are designed to fit on top of the concentric layer shapes, as Figure 11-7 shows. You can use them to represent subcomponents of a larger system.
Make sure the Snap option is enabled for this procedure. To do so, choose Tools, Snap & Glue, select the Snap check box, and then click OK.
Follow these steps to divide a layer into sections: