System Modeling and Context Models

System Modeling

• System modeling is the process of developing abstract models of a system
• Each model presents a different view or perspective of the system
• System modeling now uses graphical notations, mostly based on UML
• Models help analysts understand system functionality and communicate with customers during requirements engineering
• Models are used to derive requirements for a system
• Models are used to describe the system to engineers during the design process
• Models document the system's structure and operation after implementation

Context Models

• Context models illustrate the operational context of a system
• They show what is outside the system boundaries
• Social and organizational concerns affect where system boundaries are positioned
• Architectural models show the system and its relationship with other systems

System Perspectives

• Systems can be modeled from different perspectives
• An external perspective models the context or environment of the system
• An interaction perspective models interactions between a system and its environment, or between components of a system
• A structural perspective models the organization of a system or the structure of data
• A behavioral perspective models the system's dynamic behavior and responses to events

UML Diagram Types

• UML has 13 diagram types, but five are essential
• Activity diagrams show activities in a process or data processing
• Use case diagrams show interactions between a system and its environment
• Sequence diagrams show interactions between actors and system components
• Class diagrams show object classes and associations
• State diagrams show how a system reacts to internal and external events

Interaction Models

• Modeling user interaction helps identify user requirements
• Modeling system-to-system interaction highlights communication problems
• Modeling component interaction helps understand system performance and dependability, and potential issues
• Use case diagrams and sequence diagrams are used for interaction modeling
• Use case diagrams model interactions between a system and actors
• Sequence diagrams model interactions between system components

Use Case Modeling

• A use case is a simple description of a user's interaction with a system
• Use cases support requirements elicitation
• Each use case represents a discrete task involving external interaction
• Actors in a use case can be people or other systems
• Use cases are depicted diagrammatically and textually

Transfer-Data Use Case

• A use case in the Mentcare system represents uploading data
• The Patient Record System (PRS) is used for a general view of patient data, as opposed to details of each consultation

Tabular Description of Transfer Data Use Case

• A table describes the data, stimulus, response, and actors for the 'Transfer data' use-case.
• Includes details regarding Medical receptionist, Patient record system and data transfer protocol

Use Cases in Mentcare System

• Illustrates the various uses cases involving the role 'Medical Receptionist'

Sequence Diagrams

• Sequence diagrams are part of UML and model interactions between actors and objects within a system
• They show the sequence of interactions during a specific use case
• Objects and actors are listed at the top of the diagram
• Interactions between objects are shown by annotated arrows

Sequence Diagram for Viewing Patient Information

• Illustrates a sequence diagram for a user's action to view patient information

Structural Models

• Structural models display the organization of a system in terms of its components and relationships
• Static models show the structure of a system's design.
• Dynamic models show the organization when executing
• Structural models are used to discuss and design system architecture

Class Diagrams

• Class diagrams show object classes and associations in an object-oriented system
• An object class is a general definition of a system object type
• Associations link classes and show relationships between them
• Objects in early stages of software design often represent real-world items.

UML Classes and Associations

• Example: Relationships between Patient and Patient record, with 1 to * cardinality showing quantity

Classes and Associations in Mentcare

• Shows relationships between different categories of entities in the Mentcare system

The Consultation class

• Details of the consultation class, including fields like Doctors, Date, Time, Clinic, Reason, prescribed Medication, Prescribed Treatment, Voice Notes, and Transcript

Generalization

• Generalization is a technique to manage complexity by categorizing entities
• It infers common characteristics of classes.
• Example: Squirrels and rats are both rodents.
• It applies to software design and is implemented using inheritance.

A Generalization Hierarchy

• Shows a hierarchy of doctor specializations, with increasing specificity from 'Doctor' to more specific types.

Aggregation Model

• Displays how classes are composed of other classes, such as in a study pack or patient record
• A patient record is composed of a patient and consultations

Behavioral Models

• Models show a system's dynamic behavior during execution
• Data or events can trigger system behaviour
• Examples include real-time systems where data or events influence the ongoing process

Data-driven modeling

• Many business systems process data and generate outputs
• Data-driven models show the sequence of actions to process input data and generate outputs.

Event-Driven Modeling

• Real-time systems respond to external and internal events
• Their behavior is based on a finite number of states and transitions between them

State Machine Models

• They show system behavior, responses to stimuli and how they change states
• System states are shown as nodes, and events as arcs between states.

State Diagram of a Microwave Oven

• Illustration of states and transitions within a microwave oven

States and Stimuli for the Microwave Oven

• Lists the different states and events that can trigger transitions

Model-Driven Engineering (MDE)

• MDE is a software development approach using models rather than programs.
• Programs are generated automatically from the models and are implemented on hardware/software platforms
• It raises the level of abstraction and avoids programming language details.

Usage of Model-Driven Engineering

• It is at an early stage of development.
• Pros of MDE: Allows systems to be considered at higher levels of abstraction; Generating code automatically is cheaper
• Cons of MDE: Models for abstraction aren't always right for implementation; savings may be outweighed by implementation costs.

This quiz explores the principles of system modeling, including various perspectives and the importance of context models. It covers how models aid in understanding system functionality and communicate requirements. Test your knowledge on architectural models and their role in system design.