Figure 6 13 activity diagram in uml notation 66

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Figure 6-13 Activity diagram in UML notation
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6.6 Requirements Modeling in the Functional Perspective 81 The activity diagram above documents the sequence of actions necessary for a navigation device to calculate a route. The model documents that ini- tially the desired destination is asked for and that the current location is determined. These two actions happen concurrently, independent from one another. The input destination (object flow: object Æ destination; state Æ input) and the determined location (object flow: object Æ loca- tion; state Æ determined) are relayed. If the driver has opted to automati- cally circumvent traffic congestions, the system queries for up-to-date traf- fic information. Once the updated traffic information is received or if the driver has not selected to circumvent traffic jams, the system calculates a route to the destination. The calculated route is output to the driver. Modeling sequences of a use case Activity diagrams are well suited to document the relationships and execution conditions of main, alternative, and exception scenarios. Deci- sion nodes represent branches in the control flow between the main sce- nario and alternative and exception scenarios. Control Flow of Main and Alternative Scenarios The activity diagram in figure 6-14 shows the control flow of the main and alternative scenario of the use case “navigate to destination” as docu- mented in table 6-2. Alternative control flow branches begin at the decision nodes that document the respective alternative- and exception scenarios to a particular main scenario. Main and alternative scenarios The activity diagram shows that initially, the action “start navigation” is executed. After that, the actions “input destination” and “determine GPS coordinates” are executed concurrently and independent from one another. Once both actions have been executed, the system asks the driver if he wishes the route to be calculated dynamically (action “ask for desire to calculate the route dynamically”). If the driver does not request the route to be calculated dynamically (selection “do not avoid congestions”), no specific action is executed (see table 6-1 Æ main scenario). If the driver selects dynamic route calculation (selection “avoid congestions”), updated traffic information is determined (action “query traffic info”, see table 6-1 Æ alternative scenario). After that, the route is calculated (action “calculate route”) and output to the driver (action “output route”).
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82 6 Model-Based Requirements Documentation Figure 6-14 Documentation of the control flow of scenarios using UML activity diagrams 6.7 Requirements Modeling in the Behavioral Perspective Finite-state automata To model the dynamic behavior of a system, modeling approaches based on automata theory are typically employed. The definition of a finite-state automaton comprises a set of states and a set of transitions that, dependent on the current state of the automaton, are performed given some event.
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