1. Engineering Quality Software
Week09

2. SYST30009 - Engineering Quality Systems
Agenda
This week
Review last class
Class Diagrams
Sheridan
SYST Engineering Quality Systems

3. Class Diagrams Learning Objectives
Construct a class diagram from a narrative including relationships and multiplicities.
Identify and represent inheritance hierarchies in a class diagram.
Learn what is meant by a concrete and/or abstract class.
How to determine and note the constraints for generalization / specialization relationships.
Learn how to describe Whole-to-Part relationships on a class diagram.
How to draw all these relationships using System Architect.
Sheridan
SYST Engineering Quality Systems

4. SYST30009 - Engineering Quality Systems
Class Diagrams
Document the static structure of the system
They define what classes there are and how they are related
The symbol on the right defines the data and behaviour encapsulated by a class.
Objects “know things and know how to do things!”
Sheridan
SYST Engineering Quality Systems

5. Using System Architect
Demo exercise
Sheridan
SYST Engineering Quality Systems

6. SYST30009 - Engineering Quality Systems
Types of Objects
From last class…
Sheridan
SYST Engineering Quality Systems

7. SYST30009 - Engineering Quality Systems
Objects- Review
We need to know what types of things the user works with routinely.
Many types
Tangible
Intangible
Important to include information from all types of users
Sheridan
SYST Engineering Quality Systems

8. SYST30009 - Engineering Quality Systems
Jacobson’s Three Types
Of Objects
Entity
Interface
Control
Sheridan
SYST Engineering Quality Systems

9. Attributes & Behaviors
Behavior (methods & operations)
Real world
Data world
Sheridan
SYST Engineering Quality Systems

10. SYST30009 - Engineering Quality Systems
Class Diagram
Showing Two
Classes
Object Diagram
with Two Instances
Sheridan
SYST Engineering Quality Systems

11. Associations/Relationships
relationship among object classes
solid line connecting classes
association is named i.e. drives
where line connects to class is called “association role”
Sheridan
SYST Engineering Quality Systems

12. Associations with Multiplicity* *
shows number of objects in an association
lower..upper bound
bounds are inclusive 2..5
0..1 = optional one
0..* = optional many
1..* = many
1 = exactly one * * * * * *
Sheridan
SYST Engineering Quality Systems

13. The complexity of the Many-to-many relationships
Examples
Sheridan
SYST Engineering Quality Systems

14. SYST30009 - Engineering Quality Systems
Your turn…
SLATE – Lesson 08 Class Diagram Exercises
Sheridan
SYST Engineering Quality Systems

15. SYST30009 - Engineering Quality Systems
Sheridan
SYST Engineering Quality Systems

16. SYST30009 - Engineering Quality Systems
Subclasses
Some instances of a class (subclass) may be grouped together based on features not shared by the rest of the class.
Attributes
Behavior
Relationships
Key verb is “isakinda” (and inverse, “canbea”).
Sheridan
SYST Engineering Quality Systems

17. Subclasses and Inheritance
A subclass is made up of selected instances from another class, the “Parent class” or “superclass.”
A superclass includes all the instances of the subclass, plus possibly more as well.
Sheridan
SYST Engineering Quality Systems

18. Subclasses and Inheritance
Each subclass then adds
attributes and behaviors
that it needs but the other
one doesn’t.
Inheritance is when a subclass instance, in addition to the attributes and behavior it has by virtue of being in the subclass, also has all the attributes and behavior that instances of the superclass have.
Sheridan
SYST Engineering Quality Systems

19. Subclasses and Inheritance
The subclass relationship actually is a relationship in the way we have used that word.
It requires a verb (one in each direction).
“isakinda”
“canbea”
isakinda
canbea
Sheridan
SYST Engineering Quality Systems

20. SYST30009 - Engineering Quality Systems
Object-Oriented
To be considered truly O-O, a language, database, etc. must support:
Objects,
Classes,
Inheritance, and
Polymorphism
Sheridan
SYST Engineering Quality Systems

21. SYST30009 - Engineering Quality Systems
With subclasses, we can show more detail about relationships on our diagram.
For instance, in most companies, only managers can hire and fire.
In other words, only certain kindsa employees can do certain tasks. (only a baker can bake)
We are able to show that some relationships affect only a subclass, not every instance.
Subclasses
Sheridan
SYST Engineering Quality Systems

22. SYST30009 - Engineering Quality Systems
Your turn…
SLATE- Inheritance Exercise
Sheridan
SYST Engineering Quality Systems

23. Generalization, Inheritance & Constraints
generalization path
solid line with hollow arrowhead pointing from subclass to superclass
indicate basis of generalization
name the path for the attribute being removed = called the discriminator
discriminator shows which property is abstracted by a generalization relationship
Sheridan
SYST Engineering Quality Systems

24. Constraints on Generalization
constraints on the subclasses
overlapping: descendent may be descended from more than one of the subclasses
student can be both a research and teaching assistant
disjoint: descendent may not be descended from more than one of the subclasses
patient can not be both out and resident
Sheridan
SYST Engineering Quality Systems

25. Constraints on Generalization
complete: all subclasses are listed
only have out and resident patients
incomplete: all subclasses are not listed
more subclasses are available
can have casual, part-time employees
Sheridan
SYST Engineering Quality Systems

26. Whole-to-Part Associations
The UML provides ways to model two types of whole-to-part associations – aggregation and composition.
Jerry Kotuba
SYST30009-Engineering Quality Software

27. SYST30009-Engineering Quality Software
Definitions
aggregate: In an aggregation, the class representing the whole. aggregation: An association between classes representing a part-to-whole relationship in which the parts and the whole may exist independently and in which a single part may be associated with more than one whole at the same time.
Jerry Kotuba
SYST30009-Engineering Quality Software

28. SYST30009-Engineering Quality Software
Definitions…cont’d
composite: In a composition, a class representing the whole. composition: An association between classes representing a whole-to-part relationship in which the parts may belong to only one whole at a time and the whole does not exist without its parts.
Jerry Kotuba
SYST30009-Engineering Quality Software

29. Example of an Aggregation.
Jerry Kotuba
SYST30009-Engineering Quality Software

30. Example of a Composition.
Jerry Kotuba
SYST30009-Engineering Quality Software

31. Aggregation and Composition.
Jerry Kotuba
SYST30009-Engineering Quality Software

32. Categories of Whole-to-Part Associations
There are three relationships that sometimes occur in an object model:
Assemblies of parts
Members of groups
Containers and their contents
You may find these useful for making your model a better tool for understanding and communication.
The model can always be built without these. They do not really affect its use for system design, just for talking to the users.
Jerry Kotuba
SYST30009-Engineering Quality Software

33. SYST30009-Engineering Quality Software
Assemblies of parts
Taking something apart into its components is a technique we humans often use to understand how something works.
Often we find it improves our understanding to model
A product and its components
A business consists of branches, departments, etc.
A country consists of states, provinces, counties, boroughs, shires, towns, villages, cities, etc.
Jerry Kotuba
SYST30009-Engineering Quality Software

34. Containers and their contents
Container-Contents is a different and less common relationship.
In some situations we may find it helpful to view a relationship as one of these, e.g.,
Truck or Aircraft and the Products or Shipments that it carries
An actual shipping container and the goods it holds
A ship, bus or airplane and its passengers
A building and the businesses it houses.
Jerry Kotuba
SYST30009-Engineering Quality Software

35. Assemblies of parts Vs Containers and their contents
A Container, however, is still a perfectly good Container, even without its Contents
The jar is still OK even without the “hunny.”
And the Contents are perfectly OK without the Container
(although the “hunny” might get all over one’s paws!)
The essential difference between these relationships is that:
With Assemblies of parts, if you take the component away, the assembly (whole) probably won’t work any more
Take a wheel off a car
Take a hand off a clock
Take a leg off a table.
Jerry Kotuba
SYST30009-Engineering Quality Software

36. Collection-Member (members of groups)
Collection-Member is also a different and relatively uncommon relationship.
Sometimes we meet an actual collection:
A library full of books
An art gallery
A stamp or jewelry collection
A fleet of trucks, ships or aircraft
Other times it may help to use this to describe:
A place of worship, club or regiment and its members
An inventory of furniture or equipment
A herd, mob, flock, school or skein of animals.
Jerry Kotuba
SYST30009-Engineering Quality Software

37. SYST30009-Engineering Quality Software
How to show it in SA…
Draw the usual association link.
The “edit” the Association link and under the “aggregation” column select “aggregate” for Basic or “composite” for Composition
Jerry Kotuba
SYST30009-Engineering Quality Software

38. SYST30009-Engineering Quality Software
Your Turn…
Think about a book, which consists of a cover, table of contents, chapters and an index. Chapters in turn have pages, paragraphs and words. Show the special case of association between classes described here including the multiplicity.
Jerry Kotuba
SYST30009-Engineering Quality Software

39. SYST30009 - Engineering Quality Systems
Your turn…
SLATE – ICE04 & ICE05 Vehicle Registration System
Sheridan
SYST Engineering Quality Systems

40. SYST30009 - Engineering Quality Systems
What Comes Next?
State Diagrams
Sheridan
SYST Engineering Quality Systems