Decisions ( OOM)

A decision specifies which path to take, when several paths are possible. A decision can have one or more input flows and one or more output flows, each labeled with a distinct guard condition, which must be satisfied for its associated flow to execute some action. Your guard conditions should avoid ambiguity by not overlapping, yet should also cover all possibilities in order to avoid process freeze.

A decision can be created in the following diagrams:

Activity Diagram
Interaction Overview Diagram

A decision can represent:

A conditional branch: one input flow and several output flows. You can display a condition on the decision symbol in order to factorize the conditions attached to the flows:

Without Condition on Symbol	With Condition on Symbol
In this example, the control flow passes to the left if the age given in the application form is <18, to the right if the age is >65, and takes the another route if the age is not mentioned:	In this, the condition Total * NB + VAT > 10.000 is entered in the Condition tab in the decision property sheet, and True and False are entered in the Condition tabs of the flows:

A merge: several input flows and one output flow. In the following example, the Subscription and Charge account flows merge to become the Ship order flow:

A decision allows you to create complex flows, such as:

if ... then ... else ...
switch ... case ...
do ... while ...
loop
for ... next ...

Note: You cannot attach two flows of opposite directions to the same corner of a decision symbol.