ICOM arrows on Constraint (child, decomposition IDEF0) diagrams obey the same conventions as on Context diagrams, and the basic method for drawing them is the same. Likewise, they can be tunneled or not tunneled, as appropriate.
However, because Constraint diagrams are more complex than Context diagrams, ICOM arrows can be used in several additional ways:
▪ICOM arrows from the Parent diagram can be carried over and used on the Child diagram.
▪Because Child diagrams can have multiple Operational Activity symbols, arrows can connect one box to another on the same diagram. These are considered internal arrows.
▪Arrows headed to the same destination can join, or bundle. Likewise, arrows with a mutual origin but separate destinations can split, or unbundle.
▪An arrow can loop back to the same function it came from, as when showing iterated activity such as memory storage or feedback.
▪An arrow can be marked with a squiggle to show that a particular name applies to a particular arrow, in cases where the two are no longer adjacent on the diagram.
Looping ICOM arrows
To show iterated activity in an IDEF0 child decomposition diagram, you can draw a call or output arrow exiting from a function or activity symbol that loops back to that same box as an input or control.
In System Architect, you draw a loop by starting and ending the line on the appropriate sides of the function box. You must use the line style Straight (orthogonal) to loop ICOM Arrows. Although this is the default style, if for some reason you have changed it to Straight - any orientation or Elliptical arcs, you can set it to Straight (orthogonal) by selecting an already drawn ICOM Arrow and selecting Format, Line Style.
Tunneled ICOM arrows
When an arrow into a box is tunneled, it means that the object/data associated with the arrow does not need further understanding (or need to be modeled) on the next-level child decomposition IDEF0 diagram. System Architect will not automatically add tunneled arrows to a child IDEF0 diagram.
Tunneled arrows are notated with a parenthesis on a control on the Parent.
ICOM arrow definition
You can enter the following information about an ICOM arrow:
Glossary Text: Utilized for explaining the uses, background, or general comments to fully document each facet of the model.