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Asked By :  Tanya Spence
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1 a i uml provides notation and diagrams eg use case diagram

1. (a) (i) UML provides notation and diagrams (e.g. Use Case diagram) to support a User View/Perspective of a software system. Identify two other Views/Perspectives of a software system that UML provides for. [4 Marks] (ii) For each of the two additional views identified in (i) above, outline the main goal of the view and identify one diagram that could be developed to support its goal. [6 Marks] (b) A software system can be accessed by / interact with many users/systems. Illustrate, using example diagrams of your choice, the notation used to model different types of users and how they interact with the system. [7 Marks] (c) Discuss what is meant by Generalisation and Specialisation in terms of modelling user interaction with the system. [6 Marks] (d) Discuss what is meant by a Use Case Extended Description. In your answer, provide an example of your choice that illustrates the modelling of a normal flow and alternate flows. [10 Marks]




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Sure, I'll break down the information you requested in a structured manner.

1. (a) (i)

Question: Identify two other Views/Perspectives of a software system that UML provides for.

  1. Structural View
  2. Behavioral View

1. (a) (ii)

Question: For each of the two additional views, outline the main goal of the view and identify one diagram that could be developed to support its goal.

  1. Structural View:

    • Main Goal: The goal of the structural view is to represent the static aspects of the system, showcasing the architecture and the entities within the system, and how these entities are related.
    • Diagram: Class Diagram. This diagram shows the classes in the system, their attributes, methods, and the relationships between the classes.
  2. Behavioral View:

    • Main Goal: The purpose of the behavioral view is to illustrate the dynamic behavior of the system, focusing on how objects interact and change state based on inputs and events.
    • Diagram: Sequence Diagram. This diagram depicts how objects interact in a particular sequence, highlighting the flow of messages exchanged between them over time.

1. (b)

Question: Illustrate, using example diagrams of your choice, the notation used to model different types of users and how they interact with the system.

Example: Use Case Diagram

  • Notations:
    • Actor: Represents a type of user or another system that interacts with the system. Actors are typically depicted as stick figures.
    • Use Case: Represents a functionality or a service provided by the system to the actors. Illustrative example: an oval.
    • Association: Represents the relationship between actors and use cases. It’s depicted as a solid line connecting the actor to the use case.

Example Diagram:

     +----------------------+
     |      System          |
     |                      |
     |  (Use Case A) <----> |<----+ (Actor 1)
     |                      |
     |  (Use Case B) <----> |<----+ (Actor 2)
     |______________________|

1. (c)

Question: Discuss what is meant by Generalisation and Specialisation in terms of modelling user interaction with the system.

  • Generalisation: This refers to the abstraction of common features from multiple use cases or actors to create a generalized use case or actor. It allows the model to show shared functionality between elements, promoting reusability and simplification.

    • Example: If multiple actors (e.g., "Customer" and "Admin") share common behaviors, these behaviors can be generalized into a parent actor called "User".
  • Specialisation: This is the process where specific use cases or actors are derived from a more general element. It allows representing specialized behaviors or functionalities that extend their parent elements.

    • Example: An actor "Customer" might be specialized into "Regular Customer" and "Premium Customer," each with specific use cases.

1. (d)

Question: Discuss what is meant by a Use Case Extended Description. Provide an example illustrating the modelling of a normal flow and alternate flows.

  • Use Case Extended Description: This is a detailed textual description of a use case, providing in-depth information about the flow of events associated with the use case. It goes beyond what is depicted in simple use case diagrams by elaborating steps in the normal flow (main success scenario) and possible alternate flows (exception or error scenarios).

Example: Use Case "Withdraw Money"

  • Normal Flow:

    1. User inserts ATM card.
    2. System prompts for PIN.
    3. User enters PIN.
    4. System verifies PIN.
    5. User selects "Withdraw Money" option.
    6. User enters withdrawal amount.
    7. System checks account balance.
    8. System dispenses cash.
    9. System provides receipt.
  • Alternate Flows:

    • Invalid PIN: 1a. User enters wrong PIN. 2a. System prompts error and asks to re-enter PIN. - (Repeat up to 3 times, then capture the card if failed).

    • Insufficient Funds:

      1. User enters withdrawal amount greater than available balance.
      2. System displays "Insufficient Funds" message.
      3. User is prompted to enter a new amount or cancel the transaction.

This example delves into both normal and alternate scenarios, portraying the thoroughness of a use case extended description.

If you need more illustrations or deeper explanations, feel free to ask!


Answered By

Frances Yates

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