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System Modelling Concepts
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System Modelling Concepts
System Modelling Concepts
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Question
What is system modelling and what is its primary purpose?
Answer
System modelling is the process of developing abstract models of a system, where each model presents a different perspective of that system. Its primary purpose is to represent the system in a way that can help understand, communicate, and potentially generate a (partial or complete) system implementation from it.
Question
List at least three benefits of system modelling in software development projects.
Answer
Benefits of system modelling include: facilitating communication between users, developers, analysts, testers, and managers; exploring potential designs; validating the architectural design of the software; and being independent of programming languages and development processes.
Question
What is the Unified Modelling Language (UML) and what is it used for?
Answer
UML is a standard language used for specifying, modeling, visualizing, constructing, and documenting software systems.
Question
Name and briefly describe four types of UML diagrams mentioned.
Answer
1. Activity diagrams: show the flow of activities in a process or data processing. 2. Use case diagrams: show interactions between a system and its environment. 3. Sequence diagrams: show interactions between actors and the system and among system components. 4. Class diagrams: show the object classes in the system and associations between them. 5. State diagrams: show how the system reacts to internal and external events.
Question
How can graphical models be used in different phases of system development?
Answer
Graphical models can be used: - To facilitate discussion about a proposed system, where incomplete or incorrect models can help promote understanding. - To document an existing system, where models should accurately represent the system, though may be incomplete. - As detailed system descriptions to generate system implementation, where models must be both correct and complete.
Question
What is the difference between use case diagrams and sequence diagrams in interaction modelling?
Answer
Use case diagrams present high-level interaction between the system and its environment whereas sequence diagrams provide detailed interactions between actors and the system and between system components. They can be used together, with sequence diagrams detailing the interactions involved in a specific use case.
Question
What are use cases originally developed for, and what do they represent?
Answer
Use cases were developed to support requirements elicitation from stakeholders who interact directly with the system. Each use case represents a discrete task involving interaction with an external system.
Question
Why aren't use case diagrams intended to show the order of execution of use cases?
Answer
Use case diagrams focus on illustrating the interactions and tasks (use cases) that the system supports but do not represent the sequence or order in which these use cases are executed.
Question
What naming convention is suggested for use case names?
Answer
Use case names should start with a verb to clearly describe the task or action involved.
Question
What additional details can complement a use case diagram to better understand a use case?
Answer
Use case diagrams can be complemented by: simple textual descriptions, structured descriptions in tables, or sequence diagrams that show detailed interactions.
Question
Explain what a 'use case actor' is and illustrate with an example from the Mentcare system.
Answer
A use case actor is an entity (a person or system) that interacts with the system in a use case. In the Mentcare system, an example use case involves two actors: the operator transferring data and the patient record system with which the operator interacts.