system modeling

System modelling

Helps analysts understand system functionality; models are used to communicate with customers.

External perspective

Shows the system's context or environment.

Behavioral perspective

Shows how the system behaves.

Structural perspective

Shows the system or data architecture.

Model types

Context models, behavioral models, semantic data models, and object models.

Context model

Illustrates operational context; shows what lies outside the system boundaries.

System boundaries

Define the separation between the system and its environment.

Architectural model

Shows the system and its relationship with other systems.

Behavioral models

Describe the overall behavior of a system.

Data processing models

Show how data is processed as it flows through the system.

State machine models

Show how systems respond to events.

Data flow diagram (DFD)

Represents processing steps as data flows through a system.

Processes

Rounded rectangles showing processing steps.

Data stores

Open-ended boxes where data is held.

External entities

Squares showing outside actors.

Data flows

Arrows showing movement of data.

Insulin pump DFD

Activity/data-flow model showing control of insulin delivery.

Blood sensor

Provides data for insulin calculation.

Calculate insulin dose

Processing step.

Pump controller

Executes delivery.

State machine models

Show behavior in response to events using states and transitions.

State

A condition or mode of the system.

Transition

Movement from one state to another due to an event.

Stimuli (events)

Triggers for state transitions.

Statecharts

UML representation of state machine models.

Guards

Conditions that must be true for a transition.

Start/end states

Beginning and termination indicators (filled circle/bullseye).

Microwave oven model

State diagram for oven operation.

Stimuli

User inputs like Half Power, Full Power, Timer, Number, Door Open/Closed, Start, Cancel.

Superstate

A higher-level state that contains substates (e.g., Operation).

Semantic data model

Describes logical data structure via entities, relationships, and attributes.

Entity

A real-world item or concept.

Relationship

How entities are linked.

Attribute

Properties of entities.

Entity-Relation-Attribute model

Sets out entities, relationships, and attributes.

Data dictionary

A list of all names in system models with descriptions of entities, relationships, and attributes.

Name management

Helps avoid duplication of terms.

Organizational knowledge

Captures knowledge linking analysis, design, and implementation.

Object models

Reflect real-world entities manipulated by the system.

Object classes

Blueprints for objects; difficult to identify but reusable.

Attributes

Characteristics of objects.

Methods (operations)

Behaviours of objects.

UML (Unified Modeling Language)

A standard representation for object-oriented modelling.

Static diagrams

Class, component, deployment, interaction overview, object, package.

Dynamic diagrams

Activity, communication, composite structure, sequence, state machine, timing, use case.

Inheritance

Mechanism where classes derive attributes/services from super classes.

Multiple inheritance

Inheriting from several super classes; may cause semantic conflicts.

CASE workbenches

Tool sets supporting software process activities (analysis, design, testing).

Analysis and design workbenches

Support system modelling in requirements engineering and design.