Synchronization between System Level Sequence Diagram and Flow of Event
Sequence diagram, the most common kind of interaction diagram, focuses on the Message interchange between a number of Lifelines. System level sequence diagram is the high-level of sequence diagram which illustrates the sequence of interactions between the Use Case and the Actor who is the user of the system.
The system level sequence diagram can be transformed from the flow of events in the use case description. The VP’s products, including VP-UML and SDE, support not only the generation of system level sequence diagram based on the flow of events, but also the synchronization between the sequence diagram and flow of events.
Generating System Level Sequence Diagram from Flow of Events
Defining the flow of events is the prerequisite for generating the system level sequence diagram.
Defining Flow of Events
Let’s assume the following use case diagram is created.
The following steps show how to define the flow of events of the Withdraw Money use case.
Right-click on the
Withdraw Money use case, select
Use Case Details... from the pop-up menu.
The
New Use Case Description dialog box is shown.
Select
Main for the
Template type of the use case description. The
Use Case Details editor is then loaded automatically.
On the
Use Case Details - Withdraw Money editor, enter the
Brief Description,
Preconditions and
Post-conditions as shown below.
By identifying the interactions between the actor and the system, enter the first flow of event to the
Actor Input column as
insert card.
Right-click on the item of flow of events, select
Add Item from the pop-up menu to add a new item to the flow of event. Alternatively, press
Ctrl + Enter to add a new item.
Enter
request for PIN to the
System Response as the second flow of event.
By repeating the addition of new item to the flow of event, the flow of events is completed as shown below.
Generating Sequence Diagram
Once the flow of events has been prepared, you can generate the system level sequence diagram accordingly. To generate the system level sequence diagram:
Right-click on the
Use Case Details - Withdraw Money editor, select
Generate Sequence Diagram from the pop-up menu.
The system level sequence diagram is generated automatically.
Synchronizing Sequence Diagram to Flow of Events
In some cases, modification to the system level sequence diagram is needed after generated from the flow of events. You can directly modify the system level sequence diagram and synchronize to the flow of events.
Note: Synchronization from sequence diagram to flow of events only supports in the sequence diagram generated from the flow of events. On the contrary, create a system level sequence diagram manually cannot generate the flow of events.
Let’s assume the system level sequence diagram is modified by adding the messages 6, 9 and 10 shown below.
To synchronize the modified system level sequence diagram to the flow of events:
Right-click on the sequence diagram, select
Synchronize to Flow of Events from the pop-up menu.
The
Confirm Overwrite dialog box shows asking you to confirm overwriting the flow of events of use case details by the modified sequence diagram. Click
Overwrite to accept overwriting the flow of events.
WARNING: By clicking the
Overwrite button, the original flow of events is erased and overwritten by the messages on the sequence diagram.
The flow of events is updated automatically.
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