 Week08

 Review Schedule Weeks 8-14  This week o Review last class o Introduce Class Diagrams o ICE-03 Sheridan SYST Engineering Quality Systems 2

 Identify and analyze the objects and object-classes needed in a system  Learn how to identify and represent relationships between object classes.  Learn how to identify and create super/subclass relationships  Learn how to create a Unified Modeling Language (UML) class diagram using System Architect Sheridan SYST Engineering Quality Systems 3

 Use case o Activity the system carries out o Entry point into the modeling process  Event decomposition: help identify use cases  Elementary business processes (EBPs) o Basic unit of analysis o Initiated by event occurring at specific time and place o Discrete system response that adds business value Sheridan SYST Engineering Quality Systems 4

 Event decomposition o Develops use cases based on system response to events o Focus on business processes and business requirements  Result of the decomposition: o List of use cases triggered by business events o Use cases at the right level of analysis Sheridan SYST Engineering Quality Systems 5

 Problem domain o Set of work-related “things” in system component Things have data representation within system o Examples: products, orders, invoices, customers  OO approach to things in problem domain o Objects that interact in the system  Identify and understand things in problem domain o Key initial steps in defining requirements Sheridan SYST Engineering Quality Systems 6

Sheridan SYST Engineering Quality Systems 7

 Things can be identified with methodology  Separate the tangible from the intangible  Include information from all types of users  Ask important questions about nature of event o “What actions upon things should be acknowledged and recorded by the system?” Sheridan SYST Engineering Quality Systems 8

 List nouns users mention when discussing system  Event table as source of potential things o Use cases, external agents, triggers, response  Select nouns with questions concerning relevance o Further research may be needed Sheridan SYST Engineering Quality Systems 9

Sheridan SYST Engineering Quality Systems 10

 Analyst document entity associations ( relationships) o Example: “Is placed by” and “works in”  Associations apply in two directions o Customer places an order o An order is placed by a customer  Multiplicity: the number of associations o One to one or one to many  The associations between types of things o Unary (recursive), binary, n-ary Sheridan SYST Engineering Quality Systems 11

Sheridan SYST Engineering Quality Systems 12 Associations Naturally Occur between Things

Sheridan SYST Engineering Quality Systems 13 Multiplicity of Relationships

 Specific details of things are called attributes  Analyst should identify attributes of things  Identifier (key): attribute uniquely identifying thing o Examples: Social Security number, vehicle ID number, or product ID number  Compound attribute is a set of related attributes o Example: multiple names for the same customer Sheridan SYST Engineering Quality Systems 14

Sheridan SYST Engineering Quality Systems 15

 Domain model class diagram as UML class o OOA applies domain model class diagram to things  Problem domain objects have attributes  Software objects encapsulate attributes and behaviors o Behavior: action that the object processes itself  Software objects communicate with messages  Information system is a set of interacting objects Sheridan SYST Engineering Quality Systems 16

Sheridan SYST Engineering Quality Systems 17

Sheridan SYST Engineering Quality Systems 18

Sheridan SYST Engineering Quality Systems 19

 Generalization/specialization notation o Inheritance hierarchy o Rank things the more general to the more special Motor vehicle class includes trucks, cars, buses  Classification: means of defining classes of things o Superclass: generalization of a class o Subclass: specialization of a class Sheridan SYST Engineering Quality Systems 20

Sheridan SYST Engineering Quality Systems 21

 See SLATE Sheridan SYST Engineering Quality Systems 22

Sheridan SYST Engineering Quality Systems 23

 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 24

 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 25

 Demo exercise Sheridan SYST Engineering Quality Systems 26

 From last class… Sheridan SYST Engineering Quality Systems 27

 We need to know what types of things the user works with routinely. o Many types Tangible Intangible Important to include information from all types of users Sheridan SYST Engineering Quality Systems 28

Jacobson’s Three Types Of Objects Entity Interface Control Sheridan SYST Engineering Quality Systems 29

 Attributes  Behavior (methods & operations) o Real world o Data world Sheridan SYST Engineering Quality Systems 30

Class Diagram Showing Two Classes Object Diagram with Two Instances Sheridan SYST Engineering Quality Systems 31

 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 32

Sheridan SYST Engineering Quality Systems 33  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 * * ** ** * *

 Examples Sheridan SYST Engineering Quality Systems 34

 SLATE – Lesson 08 Class Diagram Exercises Sheridan SYST Engineering Quality Systems 35

Sheridan SYST Engineering Quality Systems 36

 Some instances of a class (subclass) may be grouped together based on features not shared by the rest of the class. o Attributes o Behavior o Relationships  Key verb is “isakinda” (and inverse, “canbea”). Sheridan SYST Engineering Quality Systems 37

 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 38

 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 39 Each subclass then adds attributes and behaviors that it needs but the other one doesn’t.

 The subclass relationship actually is a relationship in the way we have used that word.  It requires a verb (one in each direction). o “isakinda” o “canbea” Sheridan SYST Engineering Quality Systems 40 isakinda canbea

 To be considered truly O-O, a language, database, etc. must support: o Objects, o Classes, o Inheritance, and o Polymorphism Sheridan SYST Engineering Quality Systems 41

 With subclasses, we can show more detail about relationships on our diagram. o For instance, in most companies, only managers can hire and fire. o 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. Sheridan SYST Engineering Quality Systems 42

 SLATE- Inheritance Exercise Sheridan SYST Engineering Quality Systems 43

Sheridan SYST Engineering Quality Systems 44

 generalization path o 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 45

 constraints on the subclasses  overlapping: descendent may be descended from more than one of the subclasses o student can be both a research and teaching assistant  disjoint: descendent may not be descended from more than one of the subclasses o patient can not be both out and resident Sheridan SYST Engineering Quality Systems 46

 complete: all subclasses are listed o only have out and resident patients  incomplete: all subclasses are not listed o more subclasses are available o can have casual, part-time employees Sheridan SYST Engineering Quality Systems 47

 SLATE – Lesson 5 Vehicle Registration System Sheridan SYST Engineering Quality Systems 48

Sheridan SYST Engineering Quality Systems 49

 Continue with relationships o Class diagram Whole-Part associations (Aggregation) Sheridan SYST Engineering Quality Systems 50