About mapping operational activities to child diagrams
When you map operational activities to child diagrams, there are several best practices to consider.
Number of operational activities on a child OV-5 (IDEF0) diagram
According to the IDEF0 method, no child diagram IDEF0 diagram can contain fewer than three nor more than six Operational Activities. If you need more than six boxes in a child diagram, create an additional child diagram subordinate to the original child diagram. If you need fewer than three boxes, create one or two additional Operational Activities on the parent diagram rather than creating a child diagram. Since OV-5 uses the IDEF0 diagram, you should follow this rule.
Node numbers
A node number beneath the parent Operational Activity gives a reference number for the child diagram. This number is called the Detail Reference Expression (DRE.)
The IDEF0 method assigns DRE numbers using a node numbering scheme:
▪The first OV-5 diagram, the Context or A-0 diagram, contains one box, numbered 0. This diagram becomes parent to the first child diagram.
▪The first child diagram, like all child OV-5 diagrams, can contain from three to six boxes, numbered from left to right, starting at 1.
▪Thereafter, each box lends its number to any child diagram to which it becomes a parent, replacing the original 0.
For example, a child diagram of a Operational Activity on a third-level OV-5 diagram would be labeled A-3. For child diagrams on subsequent levels, numbers are formed by appending the number of the Parent box to the number of the diagram containing that Parent box. Thus, a Child of the third box in the A3 Child Diagram would be labeled A3 plus 3 or A33.