SADT Arrows
SADT arrows are used to display inputs and outputs of activities on the IDEF0 diagrams, Basic Flowcharts, and Cross-functional Flowcharts. They represent material and intangible objects that are either resources needed to perform an activity or results of this activity. You can link functional objects with an arrow on the Activity objects tab in the Properties Window of an arrow.
When an arrow is added to a diagram, no objects are associated with it. Note that you can link objects with the named arrows only.
The same object can be associated with different arrows at the same time. Removing an object from the Activity objects list of an arrow does not remove it from the Functional objects repository.
In the diagrams, when you hover over the arrow, you see the arrow name, as well as the first five objects that are associated with this arrow (Figure 1).
Arrows and Decomposition
When an activity is decomposed, its incoming and outgoing arrows (Figure 2, a) appear on the child diagram automatically (Figure 2, b), excluding EPC and BPMN diagrams.
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Delete Arrows
To delete an arrow, highlight the arrow and select Cut in the context menu or just press Del.
The dialog window with the 'Delete Arrow segment from all diagrams?' question will appear. You can select from the following options:
- Yes – Removes the arrow from all the diagrams where it is displayed;
- No – Here there are some more options:
- If an arrow links the shapes of two activities, and in their decomposition diagrams, links their children, then after deleting this arrow from the current diagram, it will still be displayed on the child diagrams. The Off-Page References will be added to its ends on the child diagrams. As a result, the arrow will only be missing from the current diagram;
- If one end of the arrow is linked to the activity shape on the current diagram and the other end is outside the diagram boundaries, then the arrow will be deleted from the current diagram and from all descendant diagrams. It will be tunneled on the above diagram;
- Cancel – Cancels the deleting operation.
Example. Deleting an Arrow
There are two activity shapes on a diagram that are linked by an arrow (Figure 3).
The diagram of each activity also contains this arrow as a boundary output and input.
When you delete an arrow from the current diagram (and select No as the answer), the off-page references appear on the decomposition diagrams (Figure 4).
If you disconnect the arrow from the off-page reference, it will appear on the parent diagram again.
Branching and Merging Arrows
One arrow may be connected to another arrow. It is called a segment arrow. The arrow to which the segment is connected, is called the main arrow.
Note that the order of connecting arrows to each other is significant: it influences arrow names and lists of activity objects.
An arrow may have branches that represent either the same thing or portions of the same thing.
Arrows may merge. Data of all segments that are merged generate the data of the main arrow.
Use the Activity objects tab of the Properties Window of an arrow to specify activity objects for each segment. The objects of segments may be copied to the Activity objects list of the main arrow and vice versa by using the Copy from segments hyperlink.
| Branching Rules |
|---|
| If an unnamed arrow (the unnamed arrow is indicated with the "#name?" label on the IDEF0 diagram) joins the named arrow, then it becomes a segment of the main arrow. The segment gets the name of the main arrow and its list of activity objects. |
| A named arrow retains its name and a list of objects when it is connected to other arrows. |
| If an unnamed arrow gets the name, all its segments get the same name (the "#name?" label disappears on the IDEF0 diagram) and the same list of activity objects. |
| You can name any unnamed segment. This will make its list of activity objects independent from that of the main arrow. |
| A segment cannot connect two arrows or be connected to the same arrow by both of its ends. |
Tunneling
A tunneled arrow is used to provide information at a specific level of decomposition that is not required for understanding at some other levels. An arrow can be tunneled at any chosen level.
An arrow can be tunneled by pressing the 
or 
button. These buttons are activated when you highlight the arrow.
| Tunneled Arrow Ends | |
|---|---|
 | The Input arrow has a tunneled end. The Output arrow has a tunneled begin. If you open a Process 2 diagram there will not be Input and Output arrows there. |
  | The arrow is missing in the parent diagram and does not have an activity at the end. |
The tunneling button is enabled in case an arrow is connected to an activity on the current diagram and to the activity’s child on the decomposition diagram. To tunnel the end of this arrow, you should first open the decomposition diagram, and disconnect the end of the arrow.
If you delete an arrow from the current diagram, and this arrow has migrated from the parent diagram, the arrow will disappear from the current diagram, and its end will be tunneled on the parent diagram.
