System Modeling with UML

• System modeling involves creating abstract representations of complex systems to understand, analyze, and predict their behavior
• System modeling defines system components, their interactions, and relationships
• System modeling utilizes graphical notation based on the Unified Modeling Language (UML)

Benefits of System Modeling

• Aids analysis and development in understanding system functionality and component interactions
• Serves as an effective means of communication for discussing system design and requirements with customers, stakeholders, and team members

Existing and Planned System Models

• Existing and planned system models play vital roles throughout the development lifecycle
• Models of existing systems represent the current state, capturing structure, behavior, and interactions as implemented or observed
• Understanding models clarifies what the current system does, depicting its functionality, structure, and interactions
• Analyzing existing system models identifies strengths and weaknesses, determining areas needing improvement or redesign
• Understanding current systems is a foundation for new requirements, ensuring new requirements address existing issues and enhance functionality
• Models of new systems represent a proposed or future system, planning its structure and behavior once implemented
• Models of the new system are used to illustrate and clarify proposed requirements to stakeholders
• Stakeholders ensure shared understanding of the new system's intended achievements.
• Engineers ensure that the design aligns with requirements by using these models to discuss and validate design proposals
• Models serve as documentation for the system's design, guiding the implementation process and providing a reference for developers
• Model-Driven Engineering (MDE) uses models as the primary means of specifying, designing, and implementing systems
• MDE focuses on creating and manipulating models to drive the development process, often involving automatic code generation and model transformations
• In a model-driven engineering process, it’s possible to generate complete or partial system implementations from system models
• Code or other artifacts may be produced, potentially accelerating the development process and reducing errors.
• Models provide clarity, facilitate communication, and support analysis and implementation in the system development lifecycle

System Perspectives

• System perspectives provide different viewpoints on a system, highlighting various aspects
• The external perspective models the context or environment in which the system operates
• The external perspective is concerned with interactions with external entities (users, other systems, external data sources)
• The external perspective helps understand the system's boundaries, its role within a larger ecosystem, and external factors
• The external perspective clarifies interactions with external stakeholders and systems, essential for defining requirements and integration points
• Use Case Diagrams and Context Diagrams are common models
• The interaction perspective models interactions between system components or the system and its environment
• Emphasizes the flow of data and control between different entities
• Interaction analysis helps in understanding and designing communication and data exchange processes within the system and with external systems
• Captures insight into how different components or entities collaborate to achieve system objectives
• Sequence Diagrams, Communication Diagrams, and Activity Diagrams are common models
• The structural perspective models the organization of a system or the structure of the data processed by the system
• Focuses on how the system is composed and how its components are arranged
• Helps understand the static structure of the system, including components, their relationships, and the hierarchy
• Provides a clear view of how data is structured, stored, and managed within the system
• Class Diagrams, Component Diagrams, Deployment Diagrams, and Entity-Relationship Diagrams are common models
• The behavioral perspective models the dynamic aspects of the system and how it responds to events and changes over time
• Captures how the system behaves in response to various inputs, changes, or events and is crucial for understanding and designing the system's response mechanisms
• Aids in defining how the system should handle different scenarios and transitions between states
• State Diagrams, Sequence Diagrams, and Activity Diagrams are common models

UML Diagram Types

• Activity Diagrams: Illustrate the activities and workflows involved in a process or data processing
• Use Case Diagrams: Depict interactions between the system and external entities (actors) and focus on the system's functionality
• Sequence Diagrams: Show the sequence of interactions between actors and the system, as well as between system components
• Class Diagrams: Represent the object classes in the system and their relationships or associations
• State Diagrams: Model the system's response to internal and external events, capturing state changes over time

Use of Graphical Models

• Graphical models aid in understanding, documenting, and implementing systems
• Facilitating discussion helps stakeholders communicate and explore system concepts, even if the models are not fully accurate or complete
• Documenting systems provides a structured and accurate representation of existing systems for reference, analysis, and communication
• Generating system implementation guides actual development and ensures the final system aligns with the design

Context Models

• Context models are used to provide a high-level view of the system and its environment
• Context models help understand the boundaries of the system, external entity interactions, and overall context
• Context models illustrate what is inside and outside the system's boundaries and help identify which elements are part of the system
• Context models show how the system interacts with external entities and helps to understand the system's interfaces and communication points
• Facilitate Stakeholder Understanding: by providing a clear picture of the system's environment and its interactions, context models help stakeholders understand the scope and constraints of the system
• Context models aid in identifying requirements related to system interactions, dependencies, and external interfaces and specify what the system should do and how it should behave in its operational environment.

Process Perspective

• Context models provide a high-level view of other systems in the environment
• Context models don't show how the system being developed interacts or is used within that environment
• Process models illustrate how the system is utilized within broader business processes
• Process models detail the interactions and flow of activities involving the system
• UML activity diagrams are commonly used to create business process models
• UML activity diagrams define the sequence of activities, control flow, and interactions involved in specific processes

Interaction Models

• Interaction models represent interactions between system components or with external entities
• Interaction models show how components or entities exchange information and control signals
• Interaction models help in understanding how the system behaves in response to events and interactions
• Interaction models facilitate the design and specification of interactions between system components

Use Case Modeling

• Use cases were developed originally to support requirements elicitation and are now incorporated into the UML
• Each use case represents a discrete task that involves external interaction with a system
• Actors in a use case may be people or other systems
• Use cases are represented diagrammatically to provide an overview of the use case and in a more detailed textual form

Sequence Diagrams

• Sequence diagrams are part of the UML and used to model the interactions between the actors and the objects within a system
• A sequence diagram shows the sequence of interactions 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

Structural Models

• Structural models show the organization and composition of a system including its components and their relationships
• Structural models focus on the static aspects of a system
• Structural models visualize system architecture and shows interconnections
• Structural models illustrate system structure and how its elements are arranged
• They act as a guide for system architecture design
• They clarify how components interact and integrate
• They ensure effective implementation.
• Structural models provide detailed documentation of the system's structure
• Structural models help manage changes

Class Diagrams

• Class diagrams are are used to show the classes in a system and the associations between classes
• An object class is a general definition of one kind of system object.
• An association is a link between classes and indicates a relationship between classes
• Objects represent what the class represents in the real world such as patient, prescription, doctor, etc.

Generalization

• Generalization is used to simplify and manage complexity by grouping entities into broader classes rather than focusing on their individual details
• Daily life categorizes experiences into general classes, inferring common traits
• System modeling identifies common attributes across classes, simplifying updates
• In object-oriented programming, Java uses class inheritance.
• Higher-level classes define attributes and operations which can be inherited by lower level functions

Aggregation Models

• Aggregation models show the relationship between components grouped together
• One components components exists inside of one or more components
• Show how components are integrated in larger structures and how structures integrate smaller objects
• Complex systems can be simplified by breaking them down into aggregate components

Behavioral Models

• Behavioral models shows dynamic system behaviors while it is executing
• They show what to expect when a system responds to stimuli from its environmental
• They reveal mechanisms behind human actions examining environmental, psychological, and social factors
• They inform the creation of programs to promote positive behavior and lower negative ones
• They can allow better meeting of needs to better a user's experience
• Help individuals improve motivations through tailored strategies
• There are two stimuli types: data & an event
• Data is information that needs to be processed
• Event is some event that triggers system processing

Data-Driven Modelling (DDM)

• Focuses on systems based on data received with minimal reliance on external events
• Illustrates the step-by-step processes in handling data and producing output
• Maps out data input to output, giving an clear picture of how systems process information

Event-driven modelling (EDM)

• Focuses on systems that repsond to various events on real time
• These models depict how a system is going to react to internal or external events
• The model assumes the system has a limit of events for which to respond
• Focus is on handling events over data processing

State Machine Models

• State machine models show how systems behave given a number of events, internal or external
• The model shows how a system transitions between events making them suitable for real-time systems
• The model is made of modes, or states, that trigger changes
• State Machine Models are represented as statecharts within Unified Modeling Language (UML)

Model Driven Engineering (MDE)

• MDE is software development focused on creating and using models in the development lifecycle
• Its approach is model-centric
• Automatic code generation is possible
• It has higher abstraction which promotes concentration on design and functionality not programming languages

Model Driven Architecture (MDA)

• MA is the beginning of Mode Driven Engineering and shares many key features;
• Model-Centric Design is emphasized to guide software design and implementation with UML
• MDA uses abstraction during model creation
• It is a foundational approach for comprehensive MDE

Types of Model

• The MDA method recommends 3 types of abstract systems:
• Computation Independent Model (CIM) which used to create domain models
• Platform Independent Model (PIM) model to derive structure and their reactions to external events
• Platform Specific Model (PSM) represents the system with details tailored to a specific platform or technology and is derived from the (PIM)

Agile Methods and MDA

• MDA proponents can support iterative development
• Conflicts with the agile principles of extensive modeling up front may make the integration challenging Automated transformations can provide executable code that can support agile integration by reducing manual coding.

Execitable UML

• Is the automated transformation of models to code
• is available through use of the subsect of UML 2, called Executable UML or xUML

Features of Executable UML

• Reduced Model Types which simplifies modeling processes by 3
  • Domain Model to identify main concerns through UML class diagrams
  • Class Models for operations and definitions
  • State model for lifecycle documentation
• Dynamic Behaviour can the specified with Object Constraint Language (OCL) which provides UML actions.