|A dynamic model
represents the behaviour of an object over time.
It is used where the object's behaviour is best
described as a set of states that occur in a
defined sequence. The components of the dynamic
purchase order (PO) is modeled as passing through
a set of states. The operations that can be
performed on the PO are dependent on the state it
is in. For example, information cannot be entered
after it has reached the approved state.
When purchase order data entry has been completed
it transitions from the entering PO
state to the pending approval state.
State transitions are modeled as being
trigger state transitions. For example, the order
mailed event triggers a state transition
from the approved to the placed
occur on state transitions. For example, on a goods
received event the action of notify
purchaser is performed. Actions are modeled
as instantaneous occurrences (contrast with
activity is performed while an object is in a
specific state. For example, while in the entering
PO state data is entered into the PO.
Activities are modeled as occurring over a period
of time (contrast with actions).