Modeling Objects and Classes, attributes, and relationships

1
Modeling Objects and Classes, attributes, and
relationships

• Data modeling
• Object structure analysis and design
• Logical data design

2
Data modeling

• Entity - person, place, thing, event or concept
  where data is collected and maintained for this
• Object structure analysis and design
  fundamental construct an object class with
  attributes and methods
• Where do find out what data is used/needed?
• Modeling the data
• ERD to Object relationship model

3
Logical data modeling concepts

• Entity only focus on data not methods
• Object Class both data and methods
• Attributes properties about an entity
• Instance of an object class
• Each object has a unique identifier (system
  maintained)
• Relationship how one entity/object is related
  to another

4
Relationship

• Cardinality minimum to maximum
• Cardinality is determined by business rules
• Each employee has maximum of three phone numbers
• Student can take up to six courses

5
Traditional Data modeling techniques

• Entity-Relationship diagram
• Entity and relation direction and cardinality

6
Object-oriented modeling technique Object
relationship model

• Object classes, attributes, and their
  relationship
• Cardinalities figure D.3
• 0 to 1, 1 to 1, 0 to many, 1 to many, many to
  many
• Collaboration relationship one instance of
  needs data contained in another instance
• Sales-transaction and customer

7
Specialization the IS-A relationship

• Subclass child
• Superclass parent
• Inheritance

8
Composition Has-A relationship

• One object is composed of one or more instances
  of another object class sales transaction has
  an st-line
• Figure D.8

9
Figure D.8a various examples
10
Identifying object classes, relationships, and
attributes

• Identifying classes candidate classes from the
  enterprise models
• Each class has data that must be retained
• More that one attribute for a class
• All instances have same attributes and methods

11
Identifying object classes, relationships, and
attributes

• Identifying relationships
• How do the classes relate to each other
• Any special or composition relationships

12
Identifying object classes, relationships, and
attributes

• Identifying object attributes
• What level of object gets the attribute
• Each attribute only once in the object model
• Attribute assigned to the class it most logically
  describes
• Bank accounts
• Account number

13
Object relationship model

• Figure D.14