Page 78 - DCAP308_OBJECT_ORIENTED_ANALYSIS_AND_DESIGN

Object Oriented Analysis and Design

Notes
Figure 6.16: State Machine with three States: “Opened”, “Closed” or “Locked”

Source: http://www.ddegjust.ac.in/studymaterial/mca-5/mca-503.pdf
The door can be in one of three states: “Opened”, “Closed” or “Locked”. It can respond to the
events Open, Close, Lock and Unlock. Notice that not all events are valid in all states; for
example, if a door is opened, you cannot lock it until you close it. Also notice that a state
transition can have a guard condition attached: if the door is Opened, it can only respond to the
Close event if the condition door Way->isEmpty is fulfilled.

Example: Let us take another example of the state diagram for an Order object as shown
in Figure 6.17. When the object enters the Checking state it performs the activity “check items.”
After the activity is completed the object transitions to the next state based on the conditions [all
items available] or [an item is not available]. If an item is not available the order is canceled. If
all items are available then the order is dispatched. When the object transitions to the Dispatching
state the activity “initiate delivery” is performed. After this activity is complete the object
transitions again to the Delivered state.
Figure 6.17: State Diagram for an Order Object

Source: http://www.ddegjust.ac.in/studymaterial/mca-5/mca-503.pdf

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