e3value user manual, first release

5.5 Cardinality dependencies

Sometimes, triggering a need triggers a value interface more than one time. This can be modeled by a cardinality dependency , which is represented by a pair of parallel lines each with a connection point that has a cardinality.

For example, in figure 5.1, each need for food results in three value transfers of Food (and consequently of Money). The cardinality dependency is triggered 5 * 100 000 times, so the value interface vi78 is triggered 15 * 500 000 = 7 500 000 times.

The default cardinalities of a cardinality dependency are 1, in which case it can be omitted from the diagram.

A cardinality dependency represents a jump in cardinality. Cardinality jumps may be up or down (figure 5.2). A jump to a higher value is called an explosion , a jump to a lower value is called an implosion.

Figure 5.2:Implosion element, and- and or-joins.

Figure 5.2 also illustrates that we can match an and- and or-splits with corresponding joins. This allows us to continue the dependency graph as a single path, in this case to a single boundary element.