System Modeling Overview

System Modeling

• System modeling is the process of creating abstract models of a system. Each model shows a different perspective of the system.
• System models can be used to understand the system's functionality. They are used to communicate with clients.
• Models can be incomplete or incorrect, but still support discussions about the system.
• Models are used to document and describe existing systems, or to describe how a proposed system will function.
• Models don't need to be complete, just accurate enough to communicate function

Topics Covered

• Context models: Display the environment of the system (what surrounds the system and what other systems it interacts with)
• Interaction models: Show interactions between the system and other systems or components. Example diagrams are use cases and sequence diagrams
• Structural models: Show the internal structure of the system. Example diagrams are class diagrams, and more complex object class diagrams (e.g., an aggregation diagram).
• Behavioral models: Display how the system behaves and reacts to external and internal events. Example diagrams are activity diagrams, state diagrams

UML Diagram Types

• Activity diagrams: Show the activities involved in processing data.
• Use case diagrams: Show interactions between a system and its environment (e.g., actors).
• Sequence diagrams: Show the sequence of interactions between actors and objects in the system.
• Class diagrams: Represent the classes and objects in the system and relationships between them (e.g., "Patient record" class interacts with "Patient" class).
• State diagrams: Show how a system reacts to events by moving through different states.

System Perspectives

• External perspective: Models the context or environment of the system.
• Interaction perspective: Models interactions between a system and its environment, or between components within the system.
• Structural perspective: Models the organization or structure of the system, and the organization of the data processed.
• Behavioral perspective: Models the dynamic behavior of a system in reaction to events.

Context Models

• Context models illustrate how a system operates in relation to other systems.
• Social and organizational concerns may influence how the boundary of the system is defined.
• Architectural models illustrate the relationship between the current system and other systems.

System boundaries

• System boundaries define what is inside and outside a system.
• They can determine the scope of the system and requirements.
• Defining system boundaries is a complex political issue.

Process Perspective

• Context models describe the environment, not how the system is used.
• Process models show how systems are used within broader business processes.
• UML activity diagrams can be used to define business process models.

Model-driven engineering (MDE)

• MDE is an approach to software development where models are the main output.
• Models often become the basis for programming instructions / code.
• Model-driven engineering focuses on developing models rather than immediately developing code.

Usage of Model-Driven Engineering

• MDA is still a new approach to software development.
• Proponents find value in the automation from models to code.
• Cons: Models are not always helpful immediately and tools in development are not widely available.
• Concerns: Implementation complexity; security; testing; dependability; legacy system compatibility.

MDA Transformations

• Model-driven architecture transitions the model from a higher-level view to a lower-level view, ultimately to executable code
• This involves translators that can achieve these transitions. These translators use various patterns and rules, based on programming language specifications.

Multiple Platform-Specific Models

• Multiple platforms will necessitate multiple translators.

Agile Methods and MDA

• MDA is meant to work with agile methods but struggles with the extensive upfront modeling required.

Adoption of MDA

• Tools are limited. Tool adaptation is resource intensive
• Modeling is not necessarily suited to all systems; there are advantages based on context.
• Concerns: Maintainability, complexity of transitioning models.

Key Points (Summary)

• Models abstract systems by ignoring implementation details including all different perspectives.
• Models can be used together to build a comprehensive system understanding.
• UML diagrams are important for visualizing and describing systems in their various states, including interaction models, object class models, and behavioral models.
• MDA is an approach toward automated, model-to-code generation, but still faces practical concerns for acceptance into broader development paradigms.

This quiz covers the essentials of system modeling, emphasizing different types of models such as context, interaction, and structural models. Each model offers a unique perspective on the system, aiding in understanding and communication with clients. Test your knowledge on how these models contribute to documenting and discussing system functionality.