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Sequence diagrams. Chapter 5 Sommerville. Sequence diagrams. Sequence diagrams are part of the UML and are used to model the interactions between the actors and the objects within a system.

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Sequence diagrams

Sequence diagrams

Chapter 5

Sommerville


Sequence diagrams1
Sequence diagrams

  • Sequence diagrams are part of the UML and are used to model the interactions between the actors and the objects within a system.

  • A sequence diagram shows the sequence of interactions that take place during a particular use case or use case instance.

  • The objects and actors involved are listed along the top of the diagram, with a dotted line drawn vertically from these.

  • Interactions between objects are indicated by annotated arrows.

Chapter 5 System modeling



Sequence diagram for transfer data
Sequence diagram for Transfer Data

Chapter 5 System modeling


Sequence diagrams2
Sequence Diagrams

  • Detail how operations are carried out

  • Dynamic Diagrams

  • Organized according to time

    • The time progresses as you go down the page

    • The objects involved in the operation are listed from left to right according to when they take part in the message sequence.

  • Create a sequence diagram for each scenario



Sequence diagrams4
Sequence Diagrams

  • Sequence diagrams show how instance exchange messages.

  • An instance can be:

    • An object, not a class

    • An actor

  • Object-Types in sequence Diagram

    • 1- interface object

    • 2-entity object

    • 3-control object

  • Sequence diagrams contain the same information as Collaboration diagrams, but emphasize the sequence of the messages instead of the relationships between the objects.


Sequence diagrams5
Sequence Diagrams

  • Messages can be Simple like

    • One object sends a message to a passive object

    • The sender does not care what happens to the message

    • Useful when the recipient can not be controlled

  • Messages can be Return messages

    • Results of procedure calls



Sequence diagrams6
Sequence Diagrams

  • Messages can be Constructors, the message creates the recipient

  • Messages can be Destructors, the message destroys the recipient.


Sequence diagrams7
Sequence Diagrams

  • Messages have sequence numbers

    • The numbers represent the order of interaction


Sequence diagrams8
Sequence Diagrams

  • Messages have sequence numbers

    • Sequence number can be hierarchical


Sequence diagrams9
Sequence Diagrams

  • Messages have a specific format

[Condition]

Sequence Number.

Return value := MessageName(Arguments)

*[iteration]

[Condition]

Sequence Number.

Return value := MessageName(Arguments)


Effective sequence diagrams
Effective Sequence Diagrams

  • Use only instances and actors

  • Concentrate on actions, not on instance static details

  • Imaging as much real time scenarios as you can, and model them

  • Keep in mind that a programmer will read your design, so make it as clear as possible.

  • Sequence diagrams contain the same information as Collaboration diagrams, but emphasize the sequence of the messages instead of the relationships between the objects.


Behavioral models
Behavioral models

  • Behavioral models are models of the dynamic behavior of a system as it is executing. They show what happens or what is supposed to happen when a system responds to a stimulus from its environment.

  • You can think of these stimuli as being of two types:

    • Data Some data arrives that has to be processed by the system.

    • Events Some event happens that triggers system processing. Events may have associated data, although this is not always the case.

Chapter 5 System modeling


Data driven modeling
Data-driven modeling

  • Many business systems are data-processing systems that are primarily driven by data. They are controlled by the data input to the system, with relatively little external event processing.

  • Data-driven models show the sequence of actions involved in processing input data and generating an associated output.

  • They are particularly useful during the analysis of requirements as they can be used to show end-to-end processing in a system.

Chapter 5 System modeling



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