System Boundaries in Systems Development

System Modeling Overview

• System modeling involves creating abstract representations of a system, offering various views or perspectives.
• Predominantly utilizes graphical notation based on Unified Modeling Language (UML).
• Assists analysts in understanding system functionality and facilitates communication with customers.

Perspectives of System Modeling

• External Perspective: Models the context or environment outside the system.
• Interaction Perspective: Models interactions between the system and its environment or its components.
• Structural Perspective: Models the organization of the system and the structure of the data it processes.
• Behavioral Perspective: Models dynamic behavior and system response to events.

UML Diagram Types

• Activity Diagrams: Illustrate the activities involved in a process.
• Use Case Diagrams: Present interactions between the system and external entities.
• Sequence Diagrams: Depict interactions among actors and system components over time.
• Class Diagrams: Display object classes in the system and relationships between them.
• State Diagrams: Show system reactions to internal and external events.

Uses of Graphical Models

• Facilitate discussions about current or proposed systems; incomplete models encourage dialogue.
• Serve as documentation for existing systems; they need to accurately represent but need not be comprehensive.
• Provide detailed descriptions aiding in the generation of system implementation.

Context Models

• Illustrate the operational context of a system and define what lies beyond system boundaries.
• Social and organizational factors may influence the definition of system boundaries.

System Boundaries

• Define what is inside versus outside the system, impacting system requirements.
• Establishing boundaries can involve political judgments based on organizational influences.

Interaction Models

• Important for identifying user requirements and communication hurdles between systems.
• Use case and sequence diagrams are used to illustrate interaction.

Use Case Modeling

• Originally developed for requirements elicitation, now integrated into UML.
• Each use case outlines a specific task involving external interaction; actors can be individuals or other systems.

Sequence Diagrams

• Part of UML, illustrating interactions during particular use cases.
• Actors and objects are indicated at the top; interactions are represented by annotated arrows.

Structural Models

• Display the organization of a system in terms of its components and their relationships.
• Can be static (design structure) or dynamic (during execution).

Class Diagrams

• Used in object-oriented system modeling to show classes and their associations.
• Classes represent definitions of system objects, and associations link related classes.

Generalization in Modeling

• A technique to manage complexity by grouping entities into more general classes.
• Facilitates change management, allowing easier updates without reviewing all system classes.

Aggregation Models

• Demonstrate how collection classes (aggregates) are composed of other classes.
• Reflect part-of relationships akin to semantic data models.

Behavioral Models

• Represent dynamic behavior of the system in response to environmental stimuli.
• Types of stimuli include incoming data requiring processing.