Unit 6

Question 1

Data Modeling

Answer 1

Data modeling represents the data view of the building blocks of a system
Note that the building blocks of the system model is classes/objects
The attributes of classes represent the data associated with the system
So, a data model uses classes, attributes, and relationships among classes.c

Question 2

Documenting Data used in Use Cases

Answer 2

The Use Case Diagram and Use Case Descriptions describe business processes and process logic
•They refer to but do not describe the data used by these processes
•So, data used by each use case will have to be documented; We call this documentation as the data dictionary
•Data Dictionary contains
1. the composition of data used within a Use Case in terms of data elements
2. the units, types, sample values, and other notes relevant for each data element

Question 3

Review Use case description for Calculate trip cost (Slide 5)

Answer 3

Do it

Question 4

Data Dictionary Notation

Answer 4

There are two types of data represented in a data dictionary
Data Element –primitive data item
Aggregate Data –composed of several data elements organized in a specific structure
For instance, suppose customer name is represented using first name, middle initial, and last name, and each of these parts of the customer name is not decomposed further (or it is not meaningful to decompose them further). Then, first name, middle initial, and last name are data elements, but customer name (as a whole) is aggregate data
Data elements do not have any specific notation to describe; however, aggregate data require specific notation to describe the structure

Question 5

Data Dictionary Notation to model aggregate data

Answer 5

symbol meaning
=   is composed of
\+   and
()  optional
[]  select one of several choices
|  alternative choices in []
{} repetition, or iteration

Question 6

Data Dictionary Notation

Answer 6

order = customer-name + shipping-address + customer-type + 1{item}10
Customer-name = First name + (middle initial) + last name
customer-type = [govt|private]
The above states that an order consists of one customer-name, one shipping address, one customer type, and at least one and a maximum of 10 items. All data elements are mandatory in an order. The customer-type will have one of the two values: govtor private. The middle initial is optional in a customer’s name.

Question 7

Description of Data Elements

Answer 7

General
data element name, aliases
definition
Format
Type, Length, Picture, Measurement unit
Control
Sourceaccess and update authorizationssecurity
Example: Date Element Name: Customer NumberAlias: Account NumberType: NumericLength: 5Picture: 99-999Source: New customer creation processUpdate: cannot be updated …

Question 8

Classes As Building Blocks

Answer 8

Classes are the building blocks of data modeling

Objects are the data units of the actual information system

Question 9

Review Finding Class Candidates Slide (11)

Answer 9

Do it

Question 10

Data Dictionary

Answer 10

Medical service = Service Code + Service name
Patient personal data = patient # + patient name + gender + date of birth
Patient contact data = address + {phone number} + email address
Appointment = patient# + service code + appointment date + appointment time + {physician name}

Question 11

Identifying Classes

Answer 11

Aggregate date are typically modeled as classes
Example: medical service and patient as classes
Data within a repeating group is typically modeled as a class
Item in the order example discussed previously
Data elements are typically modeled as attributes
Example: Service Code and Service name are attributes; since they are contained in medical service which is modeled as a class, they become attributes of the medical service class.

Question 12

Relationships

Answer 12

When an aggregate data is modeled using two or more classes, then there is probably a relationship among these classes
Appointment class is likely to be related to patient class and doctor class
Association
Aggregation
Generalization

Question 13

Association

Answer 13

Association is a structural relationship that defines the link between objects of one class with the objects of another class

Question 14

Types of Associations

Answer 14

Binary Association
Associations between exactly two different classes
•Course Section includes Students
•Members join Club

Unary Association (recursive)
Associations between two instances of the same class
•Person married to person
•A course has other courses as prerequisites

Ternary Association (three)
N-aryAssociation (between n)

Question 15

Multiplicity

Answer 15

Multiplicity specifies how many instances of one class can associate with instances of another class. Associations have minimum and maximum multiplicity
minimum is zero, the association is optional
If minimum is at least one, the association is mandatory

Question 16

Review Multiplicity Graphic (Slide 17 & 18)

Answer 16

Do it

Question 17

Review Association, Aggregation and Specialization Graphics(19,20,21)

Answer 17

Do it