Benefits of object-oriented analysis and design
- Reusability
- Recycling of program parts can reduce the costs of development in
computer based systems - Maintaining systems
- Making a change in one object has a minimal impact on other objects
Object oriented concepts: Objects
Persons/places/things that are relevant to the system being analyzed
Object oriented concepts: Classes
- Set of shared attributes and behaviors found
in each object in the class - Should have a name which differentiates it
from all other classes - Instantiate is when an object is created from a
class
o Method: Action that can be requested from
any object of the class
Object oriented concepts: Attribute
describes some property that is
possessed by all objects of the class
Object oriented concepts: Method
Action that can be requested from any object of the class
Object oriented concepts: Inheritance
- When a derived class inherits all the attributes and behaviours of the base class
- Reduces programming labor by using common concepts easily
- Feature only found in object-oriented systems
UML Concepts
- things
- relationships
- diagrams
UML things: things
- structural things
- Classes, interfaces, use cases and other elements that provide a way to create models
- Allow the user to describe relationships
UML things: behavioural things
- describe how things work
- interactions and state machines
UML things: group things
used to define boundaries
UML things: annotations things
can add notes to diagram
2 types of relationships in UML
- Structural Diagrams
- Used to describe the relations between classes - Behavioural Diagrams
- Describes the interaction between actors and a use case
3 types of UML Diagrams
- use case diagram
- use case scenario
- activity diagram
Use case diagram
- Describes how the system is used
- Starting point for UML modelling
Use case scenario
Verbal articulation of exceptions of the main behavior described by the
primary use case
Activity diagram
Illustrates overall flow of activities
Use case modelling
- Describes what the system does without describing how a system does it
- Based on the interactions and relationships of individual use cases
- Similar to the context diagram
Use case relations (behavioural)
- Communicates
- Connects an actor to a use case - Includes
- Describes the situation in which a use case contains behavior that is
common to more than one use case - Extends
- Describes situation in which use case possesses the behaviour that allows the new case to handle a variation of exception from the basic use case - Generalizes
- Implies one thing is more typical than another thing
Activity diagrams
- Shows the sequence of activities in a process
- Includes sequential and parallel activities
- Decisions that are made
Test Plans
- Activity diagrams can be used to construct test plans
- Each event must be tested to see if the system goes to the next state
- Each decision must be tested
UML steps
- Define use case model
- Continue UML diagramming to model the system during the systems analysis
phase - Develop the class diagrams
- Draw statechart diagrams
- Begin systems design by refining the UML diagrams
- Document system design in detail
